* IMlUSIETUm CCDIF about equally far apart, and joined at frequent intervals by short transverse bars. The latter are thickened, and trumpet-shaped at the base. The meshes of the whole ladder-like network formed by the beams and bars are rounded, usually oval, 35-210 ^ long and 25- 90 m broad. Most of the longitudinal beams are rhabds; some appear to be elongated rays of pentactines and hexactines. The interior of the lamellar body is occupied by rhabds and great numbers of onychhexasters, and large and small regular discohexasters. Plumicomes and a few irregular discohexasters with primary and secondary end-rays have also been found in it. Besides these spicules several large amphiasters have been observed. These are, however, most likely foreign to the sponge. Very proba- bly small hexactines also occur in the choanosome. I am not, however, certain about these spicules; the ones observed may in truth have been gastral or dermal and brought down into the choanosome accidentally. Below the surface pentac- tines are met. The superficial (dermal and gastral) skeleton consists of hexac- tines and pentactine to monactine hexactine-derivates with only five to one properly developed and one to five reduced rays, which latter appear as short, terminally rounded protuberances of the centre of the spicule. The tetractine forms are stauractines ; the diactine forms are mostly centro tyle amphioxes; a few of them appear compass-shaped. On one side of the lamella true hexactines, with all six rays fully developed, greatly predominate, spicules with only five or four fully developed rays (pentactines and stauractines) being rare, and spicules with only three or still fewer (triactines to monactines) absent altogether. On the other side of the lamella hexactine-derivates with fewer than six fully developed rays are more frequent than true hexactines and here also triactine to monactine forms with only from three to one fully developed rays are frequently LANUGONYCH I A FLABELLIJM. 105 met, the diactines being particularly abundant. Judging by analogy I should say that the surface, the skeleton of which consists chiefly of true hexactines, is gastral, the other dermal. The hexactine and pentactine forms are orientated in such manner that four of their rays extend paratangentially whilst one protrudes vertically out- ward. The stauractines, triactines, diactines, and monactines are usually extended wholly paratangentially. The rhabds are 4-20 mm. long and 5-140 m thick near the middle. Those 5-50 n thick are usually 4-7 mm. long. The slender ones are always distinctly centrotyle, the tyle being 1-6 ^ thicker than the adjacent parts of the spicule. In the stout rhabds the central tyle is only slightly developed, inconspicuous, and often altogether absent. The axial cross is equally developed in the stout non-centrotyle and the slender centrotyle rhabds. The smallest rhabds are nearly cylindrical and rounded at the ends. The rhabds 20-40 m thick in the middle taper gradually to 5-18 m towards the ends, which are usually unequally stout and simply rounded off. The large, stout rhabds generally have blunt, somewhat irregular, conic termini and are, just below the end, considerably thinner than the small slender rhabds. The measurements of five rhabds, tabulated below, indicate that these spicules are the more centrotyle and the more cylindrical the smaller they are, and vice versa. RHABDS. Length mm. Tyle Tliickness transverse diameter n difference be- tween transverse diameter of tyle and thickness of adjacent parts of the spicule of the spicule close to the tyle, near the middle of oue end fj. of the other end £i 5 19 4 15 15 12 5 23 3 20 11 5 5.7 56 3 53 12 8 6.3 53 1 52 18 14 19 80 0 (no tyle) 80 5 4 The ends of the rhabds are, for a short distance, covered with small spines. Apart from this these spicules are smooth. The spiculation of the end-parts is more conspicuous in the small than in the large rhabds. 106 LANUGONYCHIA FLABELLUM. The (hypodermal and hypogastral) pentadines (Plate 13, figs. 10, 12, 13, 16b) have an apical (proximal) ray 0.6-1 mm. long, and lateral (paratangential) rays 400-800 /*. The lateral rays of the same spicule are more or less unequal, the longest usually being 150-250 n longer than the shortest. All the rays are straight, conic, blunt, and 20-40 n thick at the base. The end-parts of the lateral rays bear quite numerous sharp-pointed spines. Proximally these spines become more blunt, lower, and less numerous, and they pass gradually into slight, hardly perceptible, flattened protuberances, finally disappearing alto- gether. The proximal parts of the lateral rays are smooth. Pentadines with very long apical rays (Plate 13, figs. 9, 16a) have also been observed. The apical (proximal) ray is in these spicules 3-9 mm. long. The lateral rays are usually broken; one intact one (Plate 13, fig. 9) was 1.85 mm. long and curved. These spicules may be foreign. Some of them are strongly corroded. A few large sword-like hexactines with the rays of one axis differently devel- oped from the rays of the other two axes have also been observed. The two rays in the differentiated axis represent the blade and the handle of the sword. The former is very long and broken off in the spicules observed. The latter is 165 n long and covered with spines. At the base it is 24-30 n thick and either cylindri- cal or terminally thickened, club-shaped. The other four rays, which represent the guard of the sword, appear to be long and equal among themselves. They were all broken off in the sword-like hexactine observed. These spicules seem to take part in the formation of the skeleton of the stalk; it is possible, however, that they are foreign. The small hexadines arid hexadine-derivates (Plate 12, figs. 24-34; Plate 13, figs. 5c, 28) always have fairly straight rays, but are, apart from this, remarkably variable and irregular. In the first place the angles between adjacent rays are not, as is generally the case in hexactinellid spicules, invariably 90°. In a good many of the tetractine (stauractine) (Plate 12, fig. 33), the triactine, and particu- larly the diactine (Plate 12, fig. 26; Plate 13, fig. 5c) forms, other than right angles are enclosed by them. This angular irregularity is particularly pro- nounced in some diactines which appear as variously opened compasses (Plate 12, fig. 26; Plate 13, fig. 5c). In the second place one to five of the rays may be reduced to mere terminally rounded protuberances arising from the centre of the spicule. Finally the reduced rays and, to a certain extent, also the fully developed rays of the same spicules are frequently unequal among themselves. In spite of this variability there are, however, absolutely no transitions between the reduced and the properly developed rays. LANUGON YCH I A FLABELLUM. 107 These hexac tines and hexactine-derivates measure 134-318 m in total diameter. Their fully developed rays are 83-180 n long and 5-14 n thick at the base. They are usually regularly conic and sharp-pointed, rarely cylindro- conic and somewhat blunt. The reduced rays are 6-25 long, 7-16 n thick, cylindrical, and terminally rounded. The length and thickness of the properly developed rays is, as the subjoined table shows, in the monactine to pentactine forms in inverse proportion to their number. The hexactine forms apparently do not conform to this rule. Since, however, the state of preservation of the specimen renders it impossible to ascertain clearly whether the not numerous larger hexactines are choanosomal or superficial, it might be assumed that these large hexactines are choanosomal spicules and do not belong to the series repre- sented by the dermals and gastrals, to which that rule applies. The small hexactines conform to the rule, and some at least of these are certainly superficial. HEXACTINES AND PENTACTINE TO MONACTINE HEXACTINE-DERIVATES. Fully developed rays Number Length Basal thickness limits n average of the longest three ,u limits /x average of the thickest three /x 6 83-140 132 5-10 9 5 90-118 114 5-9 8 4 95-125 120 6-9 8 3 100-142 141 5-11 10 2 105-160 152 6-11 10 1 123-190 1S5 10-14 13 Both the fully developed and the reduced rays are covered with spines. On the basal parts of the fully developed rays the spines are somewhat sparse and here they arise vertically. On their distal parts the spines are more numer- ous and here they point obliquely outward. The extreme tip of the ray is usually free from spines for a distance of 4 or 5 /x- The spines are conic, sharp- pointed, and 0.5-2 ^ high. Their size is in proportion to the thickness of the ray from which they arise, the stoutest rays bearing the largest spines. The cylindrical, terminally rounded, more or less knob-like, reduced rays are covered with similar spines, which are either similarly distributed as on the fully developed rays or more crowded. 108 LANUGONY CIII A FLABELLUM. It has been stated above that some of the fully developed rays are more cylindroconic and less sharply pointed than the great majority of rays. Such blunt rays have only been observed in the hexactines and pentactines, and it is always the distal protruding ray of these spicules which exhibits this peculiarity. This differentiation is interesting, since it would, if further developed and associ- ated with an increase in the size of the spines, convert these superficial hexactines and pentactines into pinules. The onychhexasters (Plate 13, figs, fib, 15b, 27) measure 86-135 m in total diameter. Their main-rays, which are regularly arranged and enclose angles of 90° with their neighbours, are 5-8 n long, thickened at both ends, and, in the middle, where thinnest, 2-3 n in transverse diameter. From the end of each main-ray several, most frequently four, branch-rays arise. These are con- siderably curved, convex to the centre of the spicule, at the base, but soon straighten out, often, however, exhibiting slight bends farther on. They are 48-60 yu, long, 1.3-2 /j. thick at the base, and gradually attenuated to 0.3-0. 6 m at the end. They bear along their length sparse, minute, backwardly directed spines, and on their ends two to four, most frequently three, slender terminal spines, 3-5 yu long. These usually enclose angles of 90-120° with the end-ray, and are curved, concave towards the centre of the spicule, or nearly straight. They generally arise from the same point, quite terminally, and form a verticil. Sometimes, however, one is situated a little below the end of the end-ray. All the discohexasters (Plate 13, figs. 1-4, 5a, 6a, 15a, 17-26) have very much the same shape, but they differ quite considerably in regard to their size and the number of their end-rays. I measured 22 of them and found that 0 was under 80 2 were 81- -100 6 U 101 -120 3 U 121 -140 0 was 141- -160 2 were 161- -180 6 u 181 -200 3 u 201- -220 0 was over 221 in total diameter. This gives the following frequency-curve (Fig. 3). From this remarkably regular double curve I conclude that two kinds of discohexasters are to be distinguished, a large kind over 150 ^ in diameter and a small kind under 150 m- LANUGONYCHIA FLABELLUM. 109 The large discohexasters measure 165-220 n in total diameter. Their main- rays, which are regularly arranged and enclose angles of 90° with their neigh- bours, are 8-10 /i long and 4.5-7 n thick. Each main-ray bears a terminal verticil of usually four end-rays, which arise steeply from the main-rays, but at once curve outwards, and are quite straight, apart from the short, curved, basal part. The basal curvature is such that the distal straight and middle-parts of all the end-rays become fairly concentric with the centre of the spicule, and also fairly equidistant; the whole discohexaster in consequence appearing as a quite regular rosette. The end-rays are 90-105 m long and 3.5-6 /x thick at the base. They are attenuated distally and are 1.5-3 m thick at their thinnest point, a short distance below the end. From here they again thicken and measure, at the end itself, 3-5 n in transverse diameter. Below the thinnest point the end- rays bear minute backwardly directed spines. The spines are rather sparse at the base of the ray but become very numerous distally towards its thinnest point. 110 LANUGONYCHIA FLABELLUM. The distal part of the end-rays, beyond the thinnest point, is smooth. At the end each end-ray bears a verticil of seven large anchor-teeth, like recurved spines with a maximum length of 11 /x. The basal parts of these terminal spines coalesce to form a kind of convex terminal disc. The transverse diameter of these terminal spine- verticils is 12-16 The constancy of the number (seven) of these terminal spines seems very remarkable, since this number is apparently in no way connected either with the triaxon (hexactine) ground plan of all hexac- tinellid spicules, or the physical (crystallographic) properties of the silica of which they consist. The small discohexasters differ from the large ones described above only in regard to their size and the number of their end-rays. They measure 82-140 n in total diameter, and have main-rays 5-8 ' /x long and 2.7-5 n thick. Each main-ray usually bears seven or eight end-rays 36-62 n in length. These measure in thickness 1.5-3 n at the base, and 0.5-1. 2 n at the thinnest point near the end, and 1-1.5 m at the end itself. The terminal spine-verticils measure 6- 11 n in transverse diameter. The plumicomes (Plate 12, figs. 21-23) have a central thickening about 3.5 m in diameter and regularly arranged main-rays, enclosing angles of 90° with their neighbours. The proximal part of the main-rays is cylindrical, and 1-1.5 /x thick. Near their end they are thickened to an oval knob, 2-3 n in transverse diameter, from which the end-rays arise. A terminal cylindrical rod, 0.8-1. 4 n thick, 2-4 /x long, and rounded at the end, arises from each knob. This rod, which lies in line with the proximal part of the main-ray, appears as its termina- tion. The total length of the main-rays (including the terminal rod) is 10-14 n. The end-rays, of which there may be about twenty on each main-ray, are curved in an S-shaped manner, and are 30-40 /x long. The irregular discohexasters with primary and secondary end-rays (Plate 12, fig. 20) are very rare. I found only three. These spicules may be malformed discohexasters. Since, however, the three observed are very much alike and since no intermediate forms connect them with the other hexaster-forms, they may also be spicules sui generis. They measure 120-140 /x in total diameter. Their main-rays, which are regularly arranged and enclose angles of 90° with their neighbours, are 5-11 m long and 3-7 n thick. Each main-ray bears two or three basally curved, but for the greater part of their length fairly straight, strongly spined, primary encl-rays. These are 50-60 /x long, 3-4 ^ thick at the base, and about 2 ^x at the end. The <3 ends of many of them are divided into short and stout, irregularly bent, trans- LANUGONYCHIA FLABELLUM. Ill verse branches. Slender secondary end-rays 8-17 n long arise from the sides and ends of the primary end-rays and their terminal branches. The basal parts of these are directed obliquely backwards towards the centre of the spicule, but they at once curve strongly outward, their distal and middle-parts being fairly straight and directed obliquely outwards. Each of these secondary end-rays bears a terminal verticil of relatively large, recurved spines, which appears as a terminal disc with strongly serrated margin. These terminal spine-verticils, which measure as much as 10 n in transverse diameter, closely resemble the terminal spine- verticils of the discohexasters above described. In examining these remarkable spicules I gained the impression that their secondary end-rays, the basal parts of which are in exactly the same position relative to the primary end-rays as the spines, might be considered as hypertrophic spines. The amphiasters, which, as stated above, I believe to be foreign, have a shaft about 13 n long and 1.2 n thick, from each end of which arise three branch-rays, sometimes 23 n long. These branch-rays bear secondary branches at the end. The known species most closely allied to the sponge described above are Mellonympha velata (Wyv. Thoms.), Lanuginella pupa 0. Schm., and certain rossellinas. It differs from all these by its spiculation to such an extent, how- ever, that a new species must be established for it. About this there can be no doubt. It is more difficult to decide in which genus this species should be placed. Is it to be assigned to one of the already established genera and if so to which one, or is a new genus to be established for it? In regard to its internal microscleres and to its large pentactines Lanugony- chia flabellum resembles most closely Mellonympha velata, the only species of Mellonympha. Since, however, its body is lamellar and thin, since its dermal spicules are reduced hexactines, mostly with only from one to four fully developed rays, since it is very doubtful whether the large pentactines observed in it pro- trude beyond the surface to form a veil, and since ordinary small, not protruding hypodermal pentactines certainly occur in it, I hardly think it advisable to place it in the same genus as this ovoid sponge with its large, freely protruding velar hypodermal pentactines and its pentactine dermals. Lanuginella pupa, the only species of Lanuginella, although also differing from Lanugonychia very considerably in shape, resembles it more closely in regard to its dermal and gastral spicules. It is, however, destitute of onych- hexasters, spicules which are very abundant in Lanugonychia flabellum. Ijima 1 1 1. Ijima. Studies on the Hexactinellida. IV. Journ. Coll. sci. Tokyo, 1904, 18, p. 12. 112 STAUROCALYPTUS HAMATUS. has indeed observed small and delicate oxyhexaster-like spicules in rare instances in Lanuginella pupa. Since, however, he considers these spicules as young stages of the discohexasters, this observation does not invalidate the correctness of F. E. Schulze’s statement 1 that the absence of onychhexasters (to which kind of spicules F. E. Schulze considers the onychhexasters to belong) is characteristic of Lanuginella. There being therefore no reason for altering this characteristic of Lanuginella I accept it and am consequently unable to place the sponge above described in Lanuginella. Since the otherwise similar species of Rossellinae differ from Lanugonychia flabellum by the absence of plumicomes, and since F. E. Schulze and I. Ijima consider the absence or presence of plumicomes in the Rossellidae as a difference sufficient for generic distinction, I do not think it advisable to place Lanugony- chia flabellum, in any of the described genera. As it seems to be most closely allied to Lanuginella and as it differs from this genus chiefly in that it possesses onychhexasters, I propose Lanugonychia, the type and, at present, only species of which is the Lanugonychia flabellum. Acanthascinae F. E. Schulze. Rossellidae with discoctasters. The collection contains one specimen of this subfamily, a new species of Staurocalyptus. STAUROCALYPTUS Ijima. Rossellidae (Acanthascinae) with oxyhexasters, small discohexasters, and discoctasters, and with hypodermal pentactines the lateral rays of which are des- titute of long curved spines. , Staurocalyptus hamatus, sp. nov. Plate 16, figs. 25-43; Plate 17, figs. 1-25; Plate 18, figs. 1-14. One specimen of this species was trawled at Station 4642 on 7 November, 1904; 1° 30.5' S., 89° 35' W. ; depth 549 m. (300 f.); the bottom was composed of broken Globigerina and molluscan shells; the bottom-temperature was 48.6°. It is characterised by the possession of numerous oxyhexactines and a few hemioxyhexasters with hook-like rays (end-rays). To this the name refers. Shape and size. The specimen has the shape of a shallow, inverted cup. 1 F. E. Schulze. Revision des systemes der Asconematiden und Rosselliden. Sitzungsb. Akad. Berlin, 1897, p. 548. STAUROCALYPTUS HAMATUS. 113 Its lower, concave side fits the dorsal side of a crustacean, apparently a species of Dicranodromia, which firmly holds the sponge on its back by the dorsally directed, last pair of thoracic extremities. In its original position the sponge completely covered the Dicranodromia dorsally (Plate 18, fig. 14). Seen from above (Plate 18, fig. 5) or below (Plate 18, fig. 6) the sponge appears oval in outline, with a protuberance at one end. It is 35 mm. long and 28 mm. broad. The wall of the inverted cup, formed by it, is about 3 mm. thick. Scattered pores are observed both on the free upper convex side and the lower concave side which rested on the back of the Dicranodromia. Those of the upper side are mostly oval, with a maximum measurement of 1 mm. in length and 0.5 in breadth. Those of the lower side are relatively broader, more nearly circular, and reach 1.5 mm. in diameter. Large prost.al rhabds protrude both from the upper and the lower side. The colour in spirit is light brown. General structure. I found a few remnants of a dermal membrane both on the concave, lower, and the marginal part of the convex, upper side. Of a gastral membrane no trace could be detected. The remnants of the soft parts in the interior indicate that the sponge has sac-shaped flagellate chambers, 80- 100 yu long and 50-70 n broad. Skeleton. Spicule-bundles, 40-200 m thick, traverse the sponge. These bundles appear to be most numerous just below the lower, concave face of the sponge, where they extend chiefly paratangentially. They are composed of rhabds — of small rhabds only, or of a large rhabcl accompanied and more or less enveloped by numerous, comital, small rhabds. Besides the rhabds forming the bundles, isolated rhabds also occur in large numbers. Oxyhexasters, hemi- oxyhexasters, and oxyhexactines with straight rays and end-rays, oxyhexactines with terminally curved, hook-like rays, and discoctasters of various size are very numerous. The last appear to be much more frequent in the interior than near the surface of the sponge. Small discohexasters, and hemioxyhexasters with rays, either all hook-like or partly hook-like and partly straight, are met with in smaller numbers. Hypodermal pentactines and a few triactine megascleres occur at, or just below, the surface. On those parts of the surface where rem- nants of the dermal membrane are left, spiny rhabds are observed. Most of these are simple diactine rhabds. Some are centrotyle, and a few possess, besides the two properly developed rays, short rudiments of one or two further rays. These spicules and a few angular diactines and stauractines, similar in regard to size and spinulation, found in the spicule-preparations, I consider as 114 STAUROCALYPTUS HAMATUS. the dermal spicules of the sponge. Spicules which might be considered as gas- trals were not observed. The choanosomal and prostal rhabds (Plate 16, figs. 25-38, 39a, b; Plate 18, fig. 13) are usually more or less curved, and exceedingly variable in size. They are 0.67-13 mm. long, and 5-175 n thick at the thickest point. The rhabds under 3 mm. in length are less than 50 n thick, those 3-9 mm. in length are 40- 100 /x thick, those over 9 mm. in length, usually 100-160 n. Although there is, as this shows, on the whole, a certain correlation between thickness and length, the proportion between these two dimensions is nevertheless very far from being constant and varies between 50 to 1 and 122 to 1. The thickest point of the rhabd may be situated at or near the middle of its length (Plate 16, figs. 29, 39a), or it may be more (Plate 16, fig. 30) or less (Plate 16, fig. 34) approximated to one of the ends. A tyle is met with only exceptionally. It is, when present, in the small rhabds 4-6 m more in transverse diameter than the adjacent parts of the spicule, and may be situated near the middle or nearer one end. Occasion- ally it lies quite terminally, in which case the spicule appears as a tylostyle. In the large rhabds the axial thread is usually somewhat thickened (Plate 16, fig. 36) at several points, but an axial cross can only rarely be made out. In the small rhabds an axial cross can generally be found. When a tyle is developed the axial cross generally lies in its centre. In the large rhabds the two rays taper towards the end and are usually abruptly and bluntly pointed (Plate 16, figs. 27, 33, 35, 37), rarely rounded or sharp-pointed. In these spicules the ends are 55 -3 as thick as the thickest portion of the middle-part. In the small rhabds the ends are cylindroconic or quite cylindrical and terminally either abruptly and bluntly pointed, like the ends of the larger rhabds (Plate 16, fig. 26), or more rounded (Plate 16, figs. 25, 27). In these spicules the ends are from half as thick to quite as thick as, or even slightly thicker than, the thickest portion of the middle-part. In the rhabds in which the thickest part lies near one end, this end is conic and stout (Plate 16, fig. 33), the other being cylindrical and slender (Plate 16, fig. 31). The whole of the rhabd, with the exception of the two ends, is smooth. The ends are covered with broad, conic, vertically arising spines 0.5-1 /x, rarely 2 /x long. The terminal spiny region is 40-230 /x long and passes, as the spines become scarcer and lower, gradually into the smooth middle-part of the spicule. In some of the rhabds an abrupt step-like attenuation occurs at a shorter or longer distance from one of the ends. Of other rhabd-irregularities noticed I mention slight transverse grooves which give to the contour an indented ap- pearance. As the figure (Plate 18, fig. 13) of such a spicule clearly shows, these STAUROCALYPTUS HAMATUS. 115 indentures are not restricted to the outer surface but affect the whole of its superficial, clearly stratified part, down to the more homogeneous central part, the surface of which also shows the indentures. The hypodermal pentadines (Plate 18, figs. 8-10) have a straight or slightly curved proximal ray, which is 0.5-2. 2 mm. long and 9-22 /x thick at the base. The lateral rays are vertical to the proximal ray and in the same spicule often unequal, the longest being 120-210 n, the shortest 80-170 tx long. All these rays are blunt. The tips of the lateral rays are spiny. A triactine with one longer and two shorter rays, opposite in the same straight line (axis), which enclosed an angle of 70° with the axis of the long ray was observed in the spicule-preparations. The long ray of this spicule was 860 n long, the two short rays were 260 and 280 n. The distal parts of all the rays were spined. The dermal spicules (Plate 16, figs. 40-43) are usually simple, straight or slightly curved, diactine rhabds (Plate 16, figs. 42, 43), 335-470 /x long, and 7- 13 ix thick at the thickest point, which is usually situated near the middle. An axial cross can usually be discerned at or near the middle. The two rays are cylindroconic and terminally rounded. Their ends are usually a half to a third as thick as the thickest portion of the middle-part of the spicule. Sometimes, however, they are thinner than that, down to a quarter of the maximum thick- ness of the middle, or thicker, up to nine tenths of this, or even slightly more. The two ends of the same spicule are usually somewhat unequal, one being 1 /x or so thicker than the other. The whole spicule is covered with conic, vertically arising spines, 0.5-2 fx long. The spines are more numerous at the ends than in the middle. This difference in the degree of spinulation of the different parts is the more clearly pronounced the longer the spicule is. Besides these simple diactine dermal rhabds similar ones with a tyle, situated either more or less centrally or, rarely, terminally, are met with. The tyle may be a simple thickening, and concentric with the axis of the spicule, or it may be one sided (Plate 16, fig. 41), or composed of two protuberances (Plate 16, fig. 40). These protuberances, which are obviously ray-rudiments, are up to 10 n long and covered with spines like the other parts of the spicule. I found in the spicule-preparations a few tetractines (stauractines) and angularly bent diactines with rays similar in regard to their spinulation to those of the rhabds above described. The former have rather unequal rays 160-230 m long and 9-10 /x thick at the base. One of the latter had rays 48 /x long, 8 ix thick at the base, and 5 m at the end. The oxyhexasters, hemioxyhexasters, and oxyhexactines with straight rays 116 STAUROCALYPTUS HAMATUS. (Plate 16, fig. 39c; Plate 17, figs. 5-8, 9b, 10b) measure 96-165 m in diameter and have from one to four end-rays. The forms with partly simple and partly bifurcated rays, that is the hemioxyhexasters with two end-rays on the branched main-rays, appear to be the most frequent. The true oxyhexasters usually have two or three, rarely three or four end-rays. The size of the spicule is, on the whole, in inverse proportion to the number of end-rays. The oxyhexactines and the hemioxyhexasters and oxyhexasters with two end-rays are 110-165 /x in diameter, the oxyhexasters with more than two end-rays on all or some of the main-rays 96-130 n in diameter. The main-rays (and simple end-rays) enclose angles of 90° with their neighbours. The simple rays are 54-84 n long, 3-4.5 n thick at the base, and conic. Their end is very slender and they terminate in an exceedingly fine point. The basal part of the ray is for a short distance smooth. Farther on it bears slender, straight, very oblique spines, which point backwards towards the centre of the spicule. The proximal spines are the largest and attain 1 ix in length. Farther on they rapidly become smaller and on the distal part of the ray no spines at all can be detected. This decrease of the size-of the spines towards the ray-end is either gradual throughout, or there is a step-like, abrupt decrease a short way up. The rays of these spicules, particularly those in which there is such an abrupt decrease of the size of the spines, resemble the threads of exploded cnidoblasts of certain hydroids. I consider these simple rays as main- rays with a single end-ray; their proximal smooth part is their main-ray, their middle and distal spined part, their end-ray. The main-rays which bear end- rays are smooth and very short, only 4-8 /x long, and 3-5.5 m thick. The end- rays arise very steeply, often nearly vertically, from the main-rays and at once curve outwards, so that their nearly straight distal and middle-parts enclose angles of 30-35° with the continuation of the main-ray axis. Apart from their basal curvature these end-rays resemble in shape and spinulation the middle and distal spined part of the simple rays above described. The end-rays are spined quite down to the base, are 37-75 /x long and 2.5-4 /x thick at the base. Rarely hemioxyhexasters are met with some rays (end-rays) straight and others hook-like (Plate 17, fig. 4). These spicules appear as transitions between the straight-rayed spicules described above and the spicules with hook-like rays to be described below. The transitional hemioxyhexaster represented (Plate 1 7, fig. 4) measures 170 ix in diameter, has two hook-like simple rays, two straight simple rays, and one main-ray with two straight end-rays. The oxyhexactines with hook-like rays (Plate 16, fig. 39d; Plate 17, figs. 1-3, 10c) measure 140-227 m in diameter. The rays of the same spicule may be equal STAUROCALYPTUS HAMATUS. 117 or unequal. The rays are, measured along the chord, 75-120 y. long, and 2.5- 8 thick at the base. They are conic and gradually attenuated to a fine point. The proximal parts of the rays are straight and regularly arranged so as to enclose angles of 90° with their neighbours. At a distance from the centre usually equal to from one half to three quarters of the length of the chord of the whole ray, the rays begin to curve either gradually or more often abruptly with a distinct angular bend. The distal part of the ray, beyond this point, is uniformly curved through an angle of at least 90°, usually more. Sometimes the curvature is so great that the end points directly backwards and the end-tangent becomes nearly parallel to the axis of the basal part of the ray (Plate 17, fig. 1). Excep- tionally the curved end-part forms nearly a whole turn (Plate 17, fig. 10c, the upper ray). In such cases it is clearly to be seen that the curvature is spiral, and it seems probable that it is of this nature also in those cases where the curved part of the ray is shorter, and the true nature of its curvature not so clearly discernible. Like the simple rays of the straight-rayed hemioxyhexasters and oxyhexac- tines described above, the rays of these spicules are smooth at the base, and farther on covered with slender, oblique, backwardly directed spines, which decrease in size distally, so that the end-part appears merely roughened or nearly smooth. Of hemioxyhexasters with hook-like rays I found only two or three. These had one bifurcate and five simple rays. One of these spicules measured 210 ^ in diameter; its simple rays were 3 m thick at the base. The small discohexasters (Plate 17, fig. lOe; Plate 18, figs. 1-4, 7, lib, 12b) measure 20-23 n in total diameter. The main-rays of the same spicule are equal and enclose angles of 90° with their neighbours. A central thickening, 3-4 n in diameter, can clearly be made out. The main-rays are smooth, 3. 5-4.5 m long, 1.2-1. 6 m thick in the middle, and thickened at both ends, proximally to the centrum, distally to the somewhat extended base, from which the end-rays arise. Each main-ray bears about 16 end-rays. The end-rays are curved, concave to the continuation of the main-ray axis, quite considerably at the base, but only very slightly, or not .at all, towards the end. They are 7-8 m long, about 0.2 n thick at the base, and attenuated towards the end, which bears a thickening about 0.8 m in transverse diameter. This terminal thickening is certainly broader than high and convex on the outer side. However, in consequence of its small size more cannot be made out about its shape. This thickening may be, and, judging by analogy, probably is, a verticil of terminal, recurved spines. 118 STAUROCALYPTUS HAMATUS. The discoctasters (Plate 16, fig. 39e; Plate 17, figs. 9cl, lOd, 11, 12, 13d, 14- 25) measure 58-320 n in diameter, usually 70-260 /z- They consist of six short and stout main-rays, each of which bears several, in the regular forms, four end-rays. Eight groups of three of these (24) end-rays, belonging to three different main-rays, usually coalesce to as many single rays, which are divided distally into verticils of about six terminal branches. The main-rays in the same spicule are equal and their axes enclose angles of 90° with those of their neighbours. They are distally rounded, 6.5-9 n long and about as thick. The six main-rays together appear as a compact central body from which arise six dome-shaped protuberances, placed in the positions of the corners of an octa- hedron. Seen from above this structure appears, when standing upright (on a corner of the octahedron), as a cross with short stout arms (Plate 17, figs. 11, 19- 23) ; when lying on one of the sides (of the octahedron) it is six-lobed in shape (Plate 17, figs. 16-18). The eight coalesced end-ray groups of three arise from the eight depressions between the dome-shaped tips of the main-rays, at points corresponding to the eight faces of the octahedron. These coalesced end-ray groups, which might be designated as pseudomain-rays, are 16-49 /z long and 3-10 M thick. They are on the whole, cylindrical, but usually somewhat irregu- lar, thickened here and there (Plate 17, figs. 14-16). The terminal branches of these pseudomain-rays, which may be designated as secondary end-rays, are slightly curved, convex to the continuation of the pseudomain-ray axis, and diverge from it at angles of 12-16°. They are 15-115 n long, 0.7-2 /z thick at the base, and attenuated towards the end, where they measure 0.4-1. 5 ^ in transverse diameter. They bear, along their length, very obliquely situated, backwardly directed spines, which are sometimes 1.5 /z long and somewhat curved. Their end is crowned by a terminal verticil of similar but stouter and more divergent recurved spines, which together form a sort of terminal disc with serrated mar- gin, 1-2.5 /z in transverse diameter (Plate 17, fig. 24). The great differences in the size of the discoctasters is due chiefly to differ- ences in the length of the secondary end-rays, 15 n in the smallest, 115 m in the largest, and to a small extent also to differences in the length of the pseudomain- rays, 16 m in the smallest, 49 /z in the largest. The main-rays are in the largest discoctasters only 3 m longer than in the smallest. Not infrequently (Plate 17, figs. 13d, 14) a simple ray (end-ray), curved at the base and straight farther on, arises directly from the central mass composed of the main-rays, between the pseudomain-rays. These simple main-rays are 27-31 m long, and 1.5-2 /z thick at the base. They are attenuated distally and FARREA OCCA SCUTELLA. 119 provided with lateral spines and a terminal verticil (“disc”) of such, like the secondary end-rays. I consider these simple rays as ordinary end-rays which have not coalesced with others to form pseudomain-rays and which are not divided distally into branches (secondary end-rays). I am inclined to consider the specimen above described as the basal part of a higher, perhaps cup-shaped, sponge, the upper parts of which may have been either nipped off by the Dicranodromia, which used it as tent and shield, or torn off during capture. Since hexactine megascleres are absent and since the sponge possesses hypodermal pentactines, mostly diactine spiny dermals, oxyhexasters, hemioxy- liexasters, microoxyhexactines, small discohexasters, and discoctasters, I think there can be little doubt that it belongs to Staurocalyptus, although its gastral spicules are unknown. It differs from all the species of this genus hitherto described by the possession of oxyhexactines and hemioxyhex asters with hook- like rays. This and other minor differences necessitate the establishment of a new species for it. EURETIDAE Zittel. Hexasterophora the body of which is calyculate or composed of ramified or anastomosing, thin-walled tubes. With a firm reticulate supporting skeleton- net. Among the free spicules are always uncinates and either scopules or clavules. With oxyhexasters or discohexasters or both. The collection contains nine more or less complete specimens and twenty fragments of this family. The generic position of two specimens and twelve fragments is doubtful. The others belong to the two genera Farrea and Eurete. FARREA Bowerbank. Euretidae with clavules, without scopules. There are four more or less complete specimens which represent a new variety of Farrea occa Bowerbank. Eight fragments apparently belong to two distinct forms which, however, cannot be specifically determined. Farrea occa scutella, var. nov. Plate 25, figs. 25-29; Plate 26, figs. 1-21; Plate 27, figs. 1-17. The collection contains four more or less fragmentary specimens of this sponge, all trawled off the southern coast of western Panama at Station 4621 on 21 October, 1914; 6° 36' N., 81° 44' W. ; depth 1067 m. (581 f.); they grew on green mud and rock; the bottom-temperature was 40.5°. 120 FARREA OCCA SCUTELLA. They resemble portions of wine-glasses with stems. To this the name of the new variety refers. Shape and size. From an extensive basal plate, which at one time was obviously attached to something hard on the sea-bottom, a short stem arises, which spreads out above to form a thin, curved, lamellar body (Plate 26, figs. 16-21). One of the specimens has two basal plates and two stems (Plate 26, figs. 18, 19). This is probably the product of a concrescence of two specimens, originally distinct, which grew side by side. The basal plate measures 5-17 mm. in maximum transverse diameter, is 1-2 mm. thick near the middle, and thins out towards the somewhat irregular lobose margin. The stem is 4-7 mm. broad and 2-3 mm. high. It consists of a vertical curved lamella, about 1 mm. thick, which appears as a portion of the wall of an upright cylindrical tube cut through longitudinally or obliquely. Above it is generally curved outward and abruptly extended into the lamella which forms the body proper of the sponge. This lamella is elegantly curved in a cylindroid or saddle-shaped manner and at the base, where it arises from the stem, is about 1 mm. thick. Towards the margin it gradually thins out. In all the specimens this lamella is more or less fragmentary. In the largest it is 19 mm. long and 18 mm. broad, measured along the chord. The colour in spirit is light brown. The skeleton consists of a network and loose hexactines, pentactines, uncinates, oxyhexasters, clavules with large teeth, and clavules with small teeth. The skeleton-net (Plate 25, figs. 25, 27-29; Plate 26, figs. 8-14, 16-21) pervades all parts of the sponge. On the lower side of the basal plate (Plate 26, figs. 10, 11) it is very dense and consists of smooth beams, 8-20 n thick, which enclose round meshes 10-40 ^ in diameter, so that this part of it appears as a perforated plate. On the upper side of the basal plate and in the stem (Plate 26, figs. 12, 13) it is composed of more or less spiny beams, 6-35 n thick, which enclose irregular, square, or triangular meshes 30-180 n wide. In this region numerous small hexactines are attached to the beams of the network (Plate 25, figs. 25, 27-29; Plate 26, figs. 12, 13) with one thickened ray. These attached tree-like hexactines are 75-135 n high. In some places other similar hexactines are soldered to these attached ones, whereby rudiments of a slender secondary network are here and there formed. In the proximal part of the lamellar body proper of the sponge the skeleton-net consists of an inner, regular layer with square, rectangular meshes (Plate 26, fig. 17), and an outer, irregular layer, with FARREA OCCA SCUTELLA. 121 chiefly triangular meshes (Plate 26, fig. 16). The marginal and middle-parts of the skeleton-net of the body-lamella (Plate 26, figs. 8, 9, 14) consist of a single layer composed of longitudinal and transverse beams. The former are in some places curved, in others straight, and spread out towards the margin of the lamella in a fan-shaped manner. Here and there they divide into two equal branches, which, at first, diverge at an angle of about 30°, but very soon become parallel ; thus the number of the longitudinal beams increases towards the margin of the body-lamella. The transverse beams are vertical to the longitudinal ones and accordingly also in some places curved, in others straight. All the beams of this network are quite smooth. The longitudinal ones are mostly 73-80 n thick, the transverse 75-90 tx. The meshes are mostly square and rectangular, more rarely quadratic, and exceptionally (where the longitudinal beams branch) triangular. The rectangular ones are 280-510 n long and 200-400 p. broad. In some places this network is remarkably regular (Plate 26, fig. 8). From each node of this network two thorns, 32-45 m thick at the base, arise in opposite directions. Both are vertical to the surface in which the network extends. One is directed dermally, the other gastrally. These thorns are fairly straight, either conic or thickened near the end, and covered with protuberances. At the base these thorns are broad, rounded, and 6-8 m high; towards the end they be- come smaller and much more slender. Of the loose spicules the uncinates and clavules with short teeth are very rare and also the hexactines rather scarce. The other kinds of loose spicules, particularly the oxyhexasters, are abundant (Plate 26, fig. 8). The fragmentary condition of the specimens renders it difficult to ascertain the position of these spicules in the sponge. I can say, however, that there is no reason to assume that they are arranged otherwise than in the type of this species where their position has been described by Schulze.1 The loose hexactines (Plate 25, fig. 26) are 110-190 n in total diameter, and have straight, conic, spined rays usually 3.5-4 /z thick at the base. The pentactines (Plate 26, figs. 8a, 15; Plate 27, fig. 6a) have regularly arranged lateral rays, usually 180-255 m long. The lateral rays of the same spicule are as a rule somewhat unequal. The difference in length between the longest and shortest is usually 15-30 ^ • Very rarely one lateral ray is greatly reduced in length, only 120 ^ long, and terminally thickened. When that is the case this difference is of course much greater. The lateral rays are straight or, more frequently, slightly and uniformly curved, concave to the proximal ray. F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 277 ff., pi. 71-73, 76, figs. 1-3. 122 FARREA OCCA SCUTELLA. They are on the whole cylindroconic, about 9 n thick at the base, and attenuated distally to 4-6 /x. The end is rounded off. Frequently a slight thickening is observed just before the end. The lateral rays are spiny. On the basal and middle-part of the rays the spines are 2-4 n high and arise vertically ; on the end- part they are 1-1.5 n high and obliquely inclined towards the end of the ray. The spines of the lateral rays are larger in the dermal pentactines than in the gastral. In the former they are larger and much more numerous on the outer side of the rays than elsewhere, the inner side being often nearly destitute of spines. On the lateral rays of the gastral pentactines the concentration of spines on the outer side is not so pronounced. The axial thread traverses the lateral rays quite to their ends. The proximal ray is straight, 180-260 m long, and usually bears only small spines near the end. In most of the pentactines, particularly the dermal ones, a rudiment of the sixth distal ray is present. This is 14-17 m long, and as thick as the other rays. It bears a few large, upwardly directed spines. Sometimes only a single terminal spine is present. In this case the distal ray (together with the spine) appears a sharp-pointed, conic thorn. The uncinates are very rare and I cannot positively assert that those ob- served in the preparations really belong to the sponge. An intact one was straight, pointed at both ends, and measured 1.6 mm. long and 10 n thick near the middle. Its spines were slender and 8 /x long. The oxyhexasters (Plate 26, figs. 1-7, 8c; Plate 27, fig. 6c) are 105-140 /x in total diameter. Their main-rays enclose angles of 90° with each other and are, in the same spicule, usually equal ; sometimes, however, considerable inequalities are observed in them, the proportion of the length of the shortest to that of the longest sometimes being 3:5. The main-rays are 22-37 /x long, straight, cylin- droconic, 2. 8-3. 8 /x thick at the base, and attenuated distally to 2-2.7 /j.. They are perfectly smooth and traversed by an axial thread, which terminates below the end and does not give off branches for the end-rays. Of end-rays there are one to four, usually two or three. The end-rays are slightly curved, concave to the continuation of the main-ray at the base, and farther on usually fairly straight, rarely considerably and irregularly curved. They are conic, uniformly attenu- ated to a fine point, 30-44 n long, 1.3-2. 2 ^ thick at the base, destitute of axial threads, and, like the main-rays, perfectly smooth. When only one end-ray is present, it extends in the continuation of the axis of the main-ray to which it belongs. When there are two they usually enclose an angle of about 60° and lie in or near a plane which passes through the main-ray from which they arise. The planes in which such end-rays extend are usually oblique to the two axial FARREA OCCA SCUTELLA. 123 planes, passing through the axis to which these forks belong and either of the two other axes of the spicule. The end-ray forks of opposite main-rays do not lie in the same plane. As far as I could make out the planes of such forks are opposite, and usually symmetrical, in such manner that the angle enclosed by them with either of the two axial planes above mentioned are supplementary; added together they give 180°. When there are three or four end-rays the most divergent usually enclose an angle of about 90°. The clavules with large teeth (Plate 27, figs. 1-5, 6b, 7-11, 13-17) are gener- ally 300-370 n long; a few are shorter, down to 210 ^ in length. They consist of a centrum, from the lower end of which there arises a shaft, and from the opposite, upper end of which arises a verticil of recurved teeth. The centrum is a short cylinder, 6.5-12.5 usually 9-12 /x, in transverse diameter, which generally bears one or a few spines at its lower end. These spines are oblique, inclined towards the shaft, and 0.5-2. 3 m long. Their size seems to be in inverse propor- tion to their number; the solitary ones are the largest. At the base, where it arises from the centrum, the shaft is 4-8 m thick; its basal part is conic; farther on it becomes nearly cylindrical; just before the end it is 2. 5-4. 5 m thick. The end is abruptly and bluntly pointed and frequently slightly thickened. The proximal and middle-parts of the shaft bear oblique spines, inclined towards its end. These spines are similar to those on the centrum, but smaller. The end-part bears stouter, vertical spines, 0.6-1. 5 n long. The number of these spines is variable. Their size appears to be in inverse proportion to their num- ber. A smooth belt sometimes intervenes between the middle region with oblique, and the terminal region with vertical spines. There are usually nine, more rarely ten, recurved teeth which form the verticil at the upper, distal end of the centrum. They are fairly equal in the same spicule, and regularly ar- ranged, the angle between adjacent ones being the same. The verticils formed by these teeth measure 39-53 m in transverse diameter. The individual teeth are conic, 5-7 m thick at the base, and uniformly attenuated towards the sharp- pointed end. They are uniformly curved, concave to the centrum, and their chords usually enclose angles of 55°-63° with the axis of the centrum and shaft. The teeth generally bear spines, sometimes 0.7 m long, some distance below their ends. These spines are confined to a median line following the outer, convex side of the teeth. Usually they form short saw-like rows on the upper margin. Sometimes they are very conspicuous (Plate 27, figs. 13, 14), sometimes so small as to be hardly visible (Plate 27, figs. 16, 17). The apex of the tooth- verticil is generally smooth and dome-like (Plate 27, figs. 1-5, 6a, 7, 8, 11, 13, 14, 16, 17). 124 FARREA OCCA SCUTELLA. Sometimes a continuation of the shaft extends beyond it, forming an apical, distally rounded, smooth protuberance, 6-7 p long and 4.5-6 p thick (Plate 27, figs. 9, 10, 15). The rare clavules with short teeth (Plate 27, fig. 12) are, apart from their teeth, similar to but smaller than the large-toothed ones above described. Their teeth are very short, hardly at all recurved, and the verticils formed by them only 18 p in diameter. Whether these clavules are young forms of the large- toothed ones, or a distinct kind of spicule, I cannot say. Their spiculation assigns these sponges to Farrea. Their shape, however, does not accord with F. E. Schulze’s diagnosis 1 of the Euretidae to which Farrea belongs, for in this diagnosis it is stated that these sponges are tubular. E. Topsent 2, who has studied a sponge very similar to the one described above, says, concerning this part of Schulze’s diagnosis, “II ne faut evidemment pas prendre ce caractere trop a la lettre” and places these sponges of his, in spite of their non-tubular shape, in Farrea. I also am disinclined to attach any great system- atic importance to that difference of shape and therefore also place the sponges above described in Farrea. Of all the known species Farrea occa Bowerbank is obviously most closely related to them. A great many specimens, by no means identical in structure and appearance, have been assigned by various authors to this species, and for some of them distinct varieties and subspecies have been established by Topsent and Wilson. Although it seems to me very doubtful whether all the sponges assigned to Farrea occa are really specifically identical and belong to this spe- cies, and although I think that the forms described as varieties and subspecies of it might very well be considered as distinct species, I provisionally accept this arrangement, because it would lead much too far to reinvestigate all these sponges, and if we accept this arrangement, we must assign to this species so wide a range of variation that the sponges described above find a place in it. Among the sponges described as Farrea occa, those for which Topsent 3 estab- lished the variety F. o. var. foliascens are obviously most closely allied to F. o. var. scutella. From these they differ by the abundance of clavules, the scarcity and size (or absence, vide supra ) of the uncinates, and the larger dimensions of the superficial pentactines. Although these differences are not very great, they are, in my opinion, quite sufficient for varietal distinction particularly 1 F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4, p. 177. 2 E. Topsent. Farrea occa (Bowerbank) var. foliascens n. var. Bull. Mus. oceanogr. Monaco, 1906, no. 83, p. 4. 3 E. Topsent. Loc. cit., 1906, p. 1. FARREA. 125 when held together with the fact that the specimens of F. o. foliascens were trawled in the tropical Atlantic, whilst the sponges described above come from the eastern Pacific. Farrea sp.? Plate 32, figs. 1-3. There are in the collection one large and three small fragments of skeleton- nets of this sponge, all trawled off the southern coast of western Panama, at Station 4631, 3 November, 1904; 6° 26' N., 81° 49' W.; depth 1415 m. (774 f.) ; they grew on green sand; the bottom-temperature was 38.0°. The large fragment (Plate 32, fig. 1) is 36 mm. long and appears as a part of the skeleton-net of a tube nearly circular in transverse section and about 10 mm. wide. Very short branch- tubes about 6 mm. wide arise from this tube, which can be considered as a main-tube. Attached to both sides of this skeleton-net are portions of network which form short tubular covered ways about 3 mm. high and broad. The skeleton-net (Plate 32, figs. 2, 3) of the main-tube and its branches forms a single layer and chiefly consists of smooth, longitudinal, and transverse beams, mostly 80-140 n thick. Here and there a short oblique beam of similar thickness is observed. The meshes are mostly square, rectangular, 350-600 /x long, and 180-240 /x broad. A few are triangular. From each node of this net- work two thorns arise, one directed towards the inner gastral surface, the other towards the outer dermal surface. These thorns are conic, vertical to the sur- face, about 50 ix thick at the base, and covered with very blunt spines. The gastral ones attain a considerable length. The skeleton-net composing the walls and roofs of the covered ways above mentioned is irregular and has mostly triangular meshes. A large number of hexactines 80-140 m in diameter are attached, with one ray, to the beams of these networks. In places, other similar hexactines are soldered to these, forming here and there a fine net. The sponges to which these skeleton-nets belonged can be assigned with a considerable degree of certainty to Farrea. Farrea sp.? There are in the collection four slightly curved, small fragments, the largest 19 mm. long, of simple skeleton-nets extending in two directions (one surface) only. These skeleton-nets were trawled in the southeastern Pacific, at Station 126 EURETE ERECTUM. 4685, on the 10 December, 1904. 21° 36.2' S., 94° 56' W. ; depth 4033 m. (2205 f.) ; they grew on dark brown clay; the bottom-temperature was 35.3°. These skeleton-nets are very regular and composed of smooth longitudinal and transverse beams, 40-60 m thick, which enclose square rectangular meshes about 750 p long and 200-350 p broad. The sponges to which these skeleton-nets belonged can be assigned with a considerable degree of certainty to Farrea. EURETE Semper. Euretidae composed of anastomosing tubes without central calyculate structure. With scopules, without clavules. The collection contains three specimens of this genus which belong to three species, one of which is new. Eurete erectum F. E. Schulze. Plate 30, figs. 1-17; Plate 31, figs. 1-28. Eurete erectum F. E. Schulze, Amerikanische Hexactinelliden, 1899, p. 72, taf. 17, figs. 1-3. Eurete erectum subsp. tubuliferum H. V. Wilson, Mem. M. C. Z., 1904, 30, p. 63, pi. 7, figs. 9, 12; pi. 8, figs. 1-3, 6. Eurete erectum subsp. gracile H. V. Wilson, Mem. M. C.Z., 1904, 30, p. 69, pi. 8, figs. 4, 5, 8, 9; pi. 9, figs. 1, 3, 5. Two specimens of this species, a fairly complete larger and a fragmentary smaller one, were trawled off the southern coast of western Panama, at Station 4622 on 21 October, 1904; 6° 31' N., 81° 44' W.; depth 1067 m. (581 f.); they grew on green sand and rock. Shape and size. The larger specimen (Plate 30, fig. 16) is a tube with quite regular circular transverse section. This tube is slightly spirally twisted, 67 mm. long, and throughout about 14 mm. in (outside) diameter. Its wall is 1-1.5 mm. thick and perforated by seven apertures. These are circular, arranged in a regular spiral, about 10 mm. wide, and surrounded by slightly protruding rims. The rims are in some places 5 mm. high and above strongly curved outward. They appear as rudiments of wide calyculate branches of the main-tube. The smaller specimen is a fragment of a similar but wider tube. It is 30 mm. long and the main-tube, of which it formed a part, must have been about 17 mm. in diameter. A thin, membranous alcyonarian colony, the outer surface of which extends in the level of the tips of the distal pinule-rays, covers large tracts of the outer dermal surface of the sponge. EURETE ERECTUM. 127 The colour in spirit is light yellowish brown. When the tube-wall is ob- served by transmitted light, numerous small dark brown spots, about 1 mm. apart, make their appearance in it. These appear to be accumulations of deep- sea ooze in the bottoms of wide, vertical, sacular canals which lead from the outer surface into the deeper parts of the tube-wall. Canal-system. The flagellate chambers (Plate 30, figs. 7c, 10c, 17c) are spherical or short oval, and measure 60-80 n in diameter. Skeleton. A special dermal and a special gastral skeleton are developed besides the internal. The internal skeleton consists of a supporting network and loose spicules; the dermal and gastral skeletons are exclusively composed of loose spicules. The supporting skeleton-net (Plate 30, figs. 4-6, 10-12, 17; Plate 31, fig. 24) appears as a lamella corresponding in shape to the tube-wall, but thinner than this. It is composed of smooth beams, 30-105 /x thick. In its outer part (Plate 30, fig. 4) the meshes are irregular, mostly triangular, the larger ones generally a little under 200 /x wide. Its inner part (Plate 30, figs. 6, 11) is more regular, composed chiefly of longitudinal and transverse beams enclosing square, rectangular meshes, mostly 370-400 ^ long, and 170-400 /x broad. Here and there small hexactines, 80-120 /x in diameter, are attached vertically to the beams of the net by one of their rays. From both faces of the lamella formed by, the skeleton-net large thorns protrude. These thorns arise from the superficial nodes of the net, point outwards, and are nearly vertical or, more rarely, oblique to the surface. They are straight or slightly curved, and quite regularly conic, pointed or, rarely, inflated at the end, and covered with broad and low, terminally rounded spines, which decrease in size distally. The thorns on the outer, dermal side (Plate 30, figs. 7e, lOe) are mostly 140-340 /x long, and 20-50 m thick at the base. The thorns on the inner, gastral side (Plate 31, fig. 24g) are larger, 230- 430 ix long, usually 270-400 fx, and 35-60 m thick at the base. The loose spicules of the choanosome are uncinates and discohexasters. The former are fairly abundant, the latter rather scarce. The dermal skeleton is composed of hexactine pinnies and small scopules. The dermal pinules are very numerous and form a continuous layer on the outer surface. Their lateral rays (Plate 30, figs. 7a, 10a, 12a, 17a; Plate 31, fig. 22) extend paratangentially and together form a network, usually with more or less quadratic meshes (Plate 31, fig. 22). Their proximal and distal apical rays are situated radially (Plate 30, figs. 7d, lOd, 12d, 17d). Their centres are on an average 130 /i apart. The dermal scopules are situated radially. Most of them 128 EURETE ERECTUM. lie below the pinule-layer and their end-ray bunches do not, as a rule, protrude beyond the surface. They are not numerous. The gastral skeleton consists of hexactine pinnies, regular and irregular, derivates of such with reduced distal apical (pinule) ray, and scopules. The pinules and pinule-derivates are very numerous and irregularly intermingled. They form, like the corresponding dermal spicules, a continuous superficial layer. Their lateral rays (Plate 30, figs. 12b, 15b, 17b; Plate 31, fig. 24b) extend para- tangentially, their apical proximal and distal rays (Plate 30, figs. 12h, 17h; Plate 31, fig. 24h) radially. The gastral scopules are situated radially. Most of them protrude a considerable distance beyond the zone of the lateral pinule- rays, and the end-ray bunches of many lie at a considerably higher level than the tips of the distal pinule-rays. The gastral scopules are much more numerous than the dermal. The dermal pinules (Plate 30, figs. 7a, d, 10a, d, 12a, d, 17a, d; Plate 31, figs. 2-5, 22) have a straight distal ray, 85-145 n long, usually 105-140 n, and at the base 8-18 n thick, usually 10-12 m- This ray is thickened above in a club-shaped manner and rounded distally. Its proximal part is smooth, its (thickened) middle- and end-parts covered with large spines. The maximal thickness of the distal ray (together with the spines) is 30-50 n, usually 40-48 n- The proximal spines are 5-8 n long, and nearly vertical to the ray, directed only slightly upwards. Distally the spines increase in size and become more and more inclined towards the tip of the ray; those arising from its summit are parallel to its axis. Half way up the spines attain the largest size. Here they are 8-13 n long. The proximal ray is usually straight. In its basal and middle- parts it is attenuated only slightly, at the end abruptly, towards the pointed end, like a Roman sword. It bears small spines near the end. The other parts of it are smooth. The proximal ray is 78-222 n long, usually 110-200 n, and at the base 6-13.5 n thick, usually 7-11 /x. The lateral rays enclose angles of 90° with each other and are, in the same spicule, fairly equal. They are similar to the proximal ray in shape and spiculation, 108-152 ^ long, usually 110-142 n, and at the base 6.5-15 n thick, usually 8-10 /x. The gastral pinules (Plate 30, figs. 1, 2, 9, 12h; Plate 31, fig. 24h) have a straight distal ray, 70-130 n long, and 11-17 n thick at the base. Its proximal part is smooth, its middle- and end-parts covered with short spines 10-17 /x long. The number of these spines is variable and never great. Sometimes there are only a few. The spines point obliquely upward and are rather irregularly distributed. The fewer there are, the more marked does this irregularity of EURETE ERECTUM. 129 their arrangement become. The proximal ray is straight, or slightly curved, and attenuated, proximally and medially very gradually, distally very abruptly towards the pointed end. It is 160-235 n long, rarely as much as 290 /x, and 8-13 (i thick at the base. Its basal and middle-parts are smooth. Near the end it bears small spines. The lateral rays are in the same spicule usually fairly equal. They are straight or very slightly curved and generally not extended in a plane, but just perceptibly bent downward towards the proximal ray. The angles enclosed between their chords and the proximal ray are consequently somewhat smaller than 90°, those between them and the distal ray somewhat larger. Apart from this they are regularly arranged, their projections on a plane vertical to the axis of the apical rays enclosing angles of 90° with each other. The lateral rays are 187-240 m long, 10-15 m thick at the base, and slightly at- tenuated to the rounded end. Their middle- and end-parts bear small and pointed (Plate 30, figs. 1, 9) or large and blunt spines (Plate 30, fig. 2). The number of these spines is never great and on the whole in inverse proportion to their size. The gastral pinule-derivates are connected with the gastral pinules above described by transitional forms, but these are remarkably rare. Most of them are fairly regular pentactines with an apical knob, the reduced distal ray; some are irregular. The regular pentactine-like gastral pinule-derivates (Plate 30, figs. 8, 13, 14). The proximal ray is usually straight, 250-320 n long, and 13-16 u thick at the base. In regard to shape and spinulation it resembles the proximal ray of the gastral pinules above described. The reduced distal ray is a rounded apical protuberance, usually 7-12 ^ high, 14-18 /x broad, and beset with a few large spines. The lateral rays of the same spicule may be fairly equal or very unequal. In extreme cases the largest are 30% longer than the smallest. The lateral rays are slightly inclined toward the proximal ray and also a little curved in this direction (concave to the proximal ray) ; sometimes they are curved also in a transverse direction. The projections of their basal parts on a plane vertical to the axis of the proximal ray, however, always enclose angles of 90° with each other. The lateral rays are 200-328 ^ long, and 14-23 m thick at the base. Distally they taper gradually and they are, at the rounded end, 7-13 m thick. They bear thick, usually quite blunt, vertically arising spines, 4-10 n long. In the middle-part of the ray these spines are large and sparsely scattered ; towards the end they become smaller, particularly more slender, and more numerous, the end itself often being quite crowded with spines. I had the impression some- 130 EURETE ERECTUM. times that the spines were arranged in elongate spiral rows ; in other cases no such spiral arrangement could be made out. Often the spines are restricted to the distal and lateral sides of the rays; sometimes, however, they are also found on the proximal side. The irregular gastral pinule-derivates (Plate 30, fig. 3) are similar to the regu- lar pentactine-like ones and differ from them only in one or two of their lateral rays resembling the distal rays of pinules. The uncinates (Plate 31, figs. 13, 14) are slightly curved or nearly straight, pointed at both ends, 0.5-1. 6 mm. long, and 4-9 m thick. Their spines are 7-27/x long, and 0.6-1 m thick at the base. They either diverge considerably (Plate 31, fig. 14) or are nearly parallel to the shaft (Plate 31, fig. 13). Their tips are 1.5- 4 m distant from the shaft. This elevation of their tips is by no means always in proportion to their length. The discohexasters (Plate 31, figs. 15, 18, 21) measure 50-70 /j. in total diameter. Their main-rays are regular, smooth, straight, 6-10 n long, and 1.6- 3 ,u thick. Each main-ray bears from one to four end-rays. These are usually curved, concave to the continuation of the main-ray at the base, and nearly straight farther on. They are 18-26 m long, 1.2-2 n thick at the base, and attenuated distally to 0.8-1. 5 The end-rays bear along their length minute recurved spines, and at the end a terminal verticil of similar but larger spines, which together form a kind of terminal disc with deeply serrated margin 2.5-4 /x in transverse diameter. It is possible that there are two kinds of discohexasters similar in size, but differing in respect to the end-rays, one with more slender and less spiny, the other with stouter and more spiny end-rays. Since, however, these asters are scarce I was unable to decide whether they all belong to the same series of forms, or whether two distinct varieties of them, as indicated above, should be distin- guished. The dermal scopules (Plate 31, figs. 16b, 17, 19) are 200-420 n long and consist of a centrum 4-10 n long and 5.5-11.5 n broad, from which arises at one end (the inner) a simple shaft, and at the opposite (the outer) a bunch of end-rays. The centrum is not well-defined, often it passes quite gradually into the shaft. It and the proximal part of the shaft are densely covered with minute spines. The shaft is straight, cylindroconic, 170-330 ^ long, 3-6 n thick at the base, and pointed at the end. Sometimes, particularly in the dermal scopules with only two end-rays, this spinulation extends quite to the end of the shaft. Some of the dermal scopules have four end-rays, others only two, and a few have three. The dermal scopules with only two end-rays are fork-like. The end-rays EURETE ERECTUM. 131 are 20-76 n long and 1-3.5 /x thick at the base. They are usually attenuated towards the end, more rarely of uniform thickness throughout. The end itself is pointed, blunt, rounded or slightly thickened to a terminal "disc,” which, however, is always small, only rarely over 3 /x in transverse diameter. The end- rays are usually curved in an S-shaped manner, rather strongly concave to the continuation of the axis of the shaft at the base, and very slightly, in the opposite direction, in their middle- and end-parts. These curvatures, particularly the basal, are subject to considerable variation. The breadth of the bunches formed by the end-rays is 11-25 /x. The end-rays are uniformly covered by densely crowded minute spines. The terminal "disc” is, when present, composed of similar but slightly larger spines. The gastral scopules (Plate 30, fig. 15i; Plate 31, figs. 1, 6-12, 16a, 20, 23, 24i, 25-28) are 0.6-1.18 mm. long, and consist of a centrum, from one (the inner) end of which arises a simple shaft, and from the opposite (outer) a bunch of end-rays. The centrum is sometimes (Plate 31, fig. 27) rather clearly defined, some- times it passes gradually into the shaft. It is 5-18 m long, 6.5-17 m broad, and bears small backwardly directed spines, like those on the adjacent parts of the shaft and the end-rays. An axial cross, composed of six axial threads regularly arranged in the usual manner, can always be detected in the centrum. One of these axial threads is long and continued in the axial thread of the shaft. The one opposite this one is short, and terminates a considerable distance below the distal end of the centrum, without giving off branches for the end-rays. The other four axial threads are still shorter and equal among themselves. Some- times four very slight elevations arise from the sides of the centrum over them. The shaft is 0.52-1.05 mm. long, straight or slightly curved, and 3-11 ix thick at the base, where it arises from the centrum. In some gastral scopules it tapers toward the end, in its basal and middle-part, very gradually, in its distal part rapidly. In most, however, its middle-part is cylindrical or thickened and is 1-3 /x, sometimes 13.5 /x thicker than the base in transverse diameter. The shaft terminates in a sharp point and is traversed throughout by an axial thread. At the base it is covered with a greater or smaller number of minute recurved spines, similar to those on the basal parts of the end-rays and on the centrum. Farther on it bears a few minute, isolated, vertical spines or is quite smooth. A little distance below the end larger vertical spines are observed. Of end-rays there are usually four ; in some gastral scopules, however, three, five, or six have been observed. The end-rays are 75-133 /x long, and 2-8 \x thick at the base. Generally the end-rays become thicker toward the distal end (Plate 31, fig. 1); sometimes they are of uniform thickness throughout (Plate 31, 132 EURETE ERECTUM. figs. 10-12) . Just below the distal end they measure 4-8 p in transverse diameter. In these measurements the fact finds its expression that the basally thin end-rays are distally thickened, whilst the basally stout ones are of uniform thickness throughout. The end-rays are destitute of axial threads and usually rather densely covered with minute recurved spines, which increase in size from the base, where they are about 0.7 p long (Plate 31, fig. 27), to the end, where they are 1.5-3 n long (Plate 31, figs. 6-9, 26). The end of the end-ray is thickened to a tyle, 12-17 p in transverse diameter. This is particularly conspicuous in the end-rays which are thin at the base and thickened distally. The distal, apical face of the tyle is dome-shaped and usually quite smooth (Plate 31, figs. 6-9). Its sides are densely covered with spines, directed obliquely downwards. The spines nearest its apex are small, farther down they rapidly increase in size, and the lowest attain 2 p or more in length. The spines of the tyle are, like those on the other parts of the end-ray, distinctly curved downwards. The end-rays are curved in an S-shaped manner, strongly, concave to the continuation of the axis of the shaft at the base, and slightly in the opposite direction in their distal and middle-parts. This second (outward) curvature is sometimes so light that the distal part of the end-ray appears straight. The degree of divergence of the end-rays is variable. The bunch formed by them is 60-102 p broad. • As examples the measurements of three gastral scopules of various dimen- sions are tabulated below. Total length p 760 920 1180 Breadth of the bunch of end-rays p 64 80 62 Shaft length p 642 789 1050 thickness in the middle p 8.5 9 12 at the base p 6.5 8 9 Centrum length p 13 18 10 thickness p 12 15 13 End-rays length p 105 113 120 thickness at the base p 3.5 5 5 just below the terminal tyle p 4.5 8 5 transverse diameter of the terminal tyle p 15 16 12 EURETE ERECTUM. 133 The statements given above show that the sponges here described are very similar to Eurete erecturn F. E. Schulze.1 Wilson has established three subspecies of this species: — tubuliferum ,2 mucronatum ,3 and gracile .4 One of these, E. e. mucronatum, differs from the sponges above described, and also from Schulze’s type, and from the other two of Wilson’s subspecies, by possessing oxyhexasters instead of discohexasters. This difference is in my opinion of such systematic importance that I consider it distinct from the other sponges placed in Eurete erecturn. After the exclusion of this subspecies, Schulze’s Eurete erecturn , Wilson’s E. e. tubuliferum, Wilson’s E. e. gracile, and the sponges described above, remain as forms of one species. A comparison of these shows, that, although similar in the main, they differ from each other in several minor points. The tubular body of the sponge is in Schulze’s type dichotomously branched, in the three others simple. This tube is in Wilson’s E. e. tubuliferum and in my specimens 14-17 mm. wide, in Schulze’s type and in Wilson’s E. e. gracile 8-12 mm. The distal rays of the dermal pinnies are in Wilson’s E. e. gracile 50 m thick, in Schulze’s type and in Wilson’s E. e. tubuliferum only 35-40 /z. In the specimens examined by me, dermal pinules occur together with distal rays as stout as those of E. e. gracile and as slender as those of the other two. In my specimens the lateral and proximal rays of the gastral pentactine-like pinule-derivates are considerably larger than the corresponding rays of the gastral pinules proper. In the other three no such difference occurs, their gastral pinules and pinule-derivates being about as large as the gastral pinules of my specimens. The greatest differences between these sponges are met with in their scopules. To facilitate a comparison between the scopules of these sponges, short descriptions of them are tabulated on p. 134. In respect to their other characters, particularly the shape and size of the uncinates and discohexasters, the four groups of forms appear to agree quite closely. Schulze’s type was collected at Albatross Station 2819, near the Gala- pagos Islands, depth 717 m. ; Wilson’s E. e. tubuliferum at the Albatross Stations 3358 and 3359, off the south coast of western Panama, depth 875 and 1015 m.; Wilson’s E. e. gracile at Albatross Station 3380, Gulf of Panama, depth 1693 m. ; and the specimens examined by me at Albatross Station 4622, off the south coast of western Panama, depth 1067 m. The differences between 1 F. E. Schulze. Amerilcanische Hexactinelliden, 1899, p. 72, taf. 17, figs. 1-3. 2 //. V. Wilson. Mem. M. C. Z., 1904, 30, p. 63, pi. 7, figs. 9, 12; pi. 8, figs. 1-3, 6. 3 H . V. Wilson. Loc. cit., p. 68, pi. 8, fig. 7. 4 H. V. Wilson. Loc. cit., p. 69, pi. 8, figs. 4, 5, 8, 9, pi. 9, figs. 1, 3, 5. 134 EURETE ERECTUM. SCOPULES OF THE DIFFERENT FORMS OF EURETE ERECTUM. A In Schulze’s type B In E. e. tubuliferum Wilson. C In E. e gracile Wilson. D In the specimens ex- amined by me. Dermal scopules Total length 200- 600 n) 4-6 end-rays with pointed, re- curved spines and terminal tyle with larger spines on lower side. Two kinds. In one 3-4 cylindrical end- rays, 40 by 2 n, with minute sharp dentic- ulations and small smooth terminal tyle; centrum distinct; shaft 200-240 by 4 fx. In the other 4-10 end-rays, 60-100 by 2-3 1±, with minute sharp denticulations and a terminal tyle 5-8 ij. in diameter, sometimes with re- curved spines; shaft a little longer than in the other form, 6 ix thick. Two kinds. In one 4 end-rays, 50-70 by 4-6 ix, tapering dis- tally, with minute denticulations bas- ally, smooth distally, without tyle or a very small terminal tyle; shaft 300 by 6-8 ix. In the other 4-6 cylindrical end- rays, 70-100 by 3-5 ix, slightly roughened, with terminal tyle 6-12 ix in diameter, and spines. Total length 600-700 ix. Total length 200- 420 /x. 2 or 4, rarely 3 end-rays. 20-76 by 1-3.5 /x at the base, attenuated distally or cylindrical, the end pointed, rounded, or slightly thickened, densely covered with minute spines. Shaft 3-6 ix thick. Gastral scopules Similar to the dermal but larger on the whole and with more divergent end-rays, these more frequently angularly bent. 4-6 end-rays 70-80 m long, either smooth, 2 fx thick at base, and thickened to 4 /x dis- tally, with terminal tyle 12 ix in diameter with recurved spines on the lower side; or cylindrical, with mi- nute denticulations, with terminal tyle 8 ix in diameter; or transitions between these; shaft 300 by 5 ix. 3-6 end-rays, 100- 120 ix long, either cy- lindrical, 4-5 ix thick, with terminal tyle, 12 ix in diameter with recurved spines ; or 12 ix thick at base and tapering distally, without terminal tyle ; or transitions be- tween these. Total length 0.6-1. 5 mm.; shaft 8-16 ix thick. Total length 0.6- 1.18 ix. 3-6, usually 4 end-rays, 75-133 by 2-8 ix at base, thickened distally or, rarely, cylindrical. Densely covered with minute recurved spines, with semi- spherical terminal tyle 12-17 ix in diam- eter, with large re- curved spines below. Shaft at base 4-11 ix thick. the specimens examined by Schulze and Wilson and those described in this paper indicate that the former differ from the latter quite as much as the latter differ among themselves. This is particularly noticeable in that the former possess dermal scopules with only two end-rays, which are absent in the latter, and that the gastral pentactine-like pinule-derivatives of the former are much larger than the corresponding spinules of the latter. The general agreement of all these sponges, the localities from which they were obtained, and particularly the fact that the differences between them appear to be virtually confined to the superficial spicules, which are of course most liable to be influenced by the environment, make it very doubtful, however, whether they should be considered EURETE SPINOSUM. J35 as distinct subspecies. To me it seems that a subdivision of the species into four local forms (A, B, C, and D) adapted to different surroundings, but congenitally hardly at all different, would more correctly express the relation between them. Their distinctive features are the following: — Eurete erectum A. ( Eurete erectum F. E. Schulze, 1899). Main-tube dichotomous. One kind of scopule with 4-6 end-rays with terminal tyle. Total length of scopules 400-600 ^ . Eurete erectum B. ( Eurete erectum subsp. tubuliferum Wilson, 1904). Main-tube simple. Several kinds of scopules with 3-10 end-rays, all with terminal tyle. Total maximum length of scopules 400 m- Distal ray of dermal pinules under 40 ^ thick. Eurete erectum C. ( Eurete erectum subsp. gracile Wilson, 1904). Main-tube simple. Several kinds of scopules with 3-6 end-rays. These in some with terminal tyle, in others distally attenuated and without tyle. Total length of longest gastral scopules 1.5 mm. Distal ray of dermal pinules 50 fx thick. Eurete erectum D. Main-tube simple. Several kinds of scopules. Some small dermal ones with only 2 end-rays without terminal tyle. The others with 3-6 end-rays. These either distally thickened and with terminal tyle or, more rarely, cylindrical or attenuated distally, without terminal tyle. Total length of largest gastral scopules 1.18 mm. Eurete spinosum, sp. nov. Plate 29, figs. 1-26. One fragmentary specimen of this species was trawled off northern Peru, west southwest of Aguja Point, at Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4062 m. (2222 f.) ; it grew on fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. The lateral rays of its superficial pent-actines bear exceedingly large spines. To this the name refers. Shape and size. The single specimen is a lamellar fragment 25 mm. long, 20 mm, broad, and 2 mm. thick. It is curved in one direction, the radius of 136 EURETE SPINOSUM. curvature being about 20 mm., and may originally have formed part of a cylindri- cal tube about 40 mm. in diameter. The colour in spirit is dirty brown. The skeleton consists of a continuous net, which pervades the whole lamella, and of loose pentactines, hemioxyhexasters, and scopules. Long, slender rhabds have also been observed, but it is doubtful whether they belong to the sponge. The pentactines form a continuous layer on the intact parts of the surface. Their lateral rays extend paratangentially, their apical ray points inward. The hemioxyhexasters are exceedingly numerous and appear, so far as can be judged by the fragmentary specimen, to occur in dense masses in all parts of the choanosome. The large (perhaps foreign) rhabds lie more or less parallel to the surface. The skeleton-net (Plate 29, figs. 18, 19, 23-25) is by no means uniform in structure throughout the thickness of the lamella. In the dermal zone (Plate 29, figs. 18, 23) it is rather irregular, composed of beams 8-40 ^ thick, usually 20- 35 m, and here its meshes are triangular or irregularly square, not rectangular, and 0.2-0. 4 mm. wide. In the gastral zone (Plate 29, figs. 19, 25) on the other hand the network is very regular, composed of longitudinal and transverse beams. The former are 18-50 m thick, and on an average about 0.23 mm. apart; the latter are 8-36 m thick, and individually usually extend obliquely but col- lectively from zones which are 0.8-1 mm. apart, and extend transversely, vertical to the longitudinal beams, quite across the whole specimen. With the exception of a few, usually thin ones, which are quite smooth, the beams of the skeleton-net are covered with conic spines, 2.5-8 m high, mostly 5-6 fx. The spines of the thin and thick beams are nearly equal in height but differ, often very considerably, in breadth, those on the thicker beams being usually much stouter than those on the thinner beams. Freely terminating rays of the hexactines, by whose concres- cence the network seems chiefly to be formed, arise from the beams in many places. These spine-like protuberances are thinner than the beams of the net- work and are only 4 ^ thick. Here and there local thickenings are observed in the beams. Cylindroconic, terminally rounded spines attaining 25 n in length and 9 n in thickness arise from these thickenings. These spines are parallel to the surface of the sponge and the thickenings from which they arise also chiefly extend in this direction. The thickenings with their spines have a cockscomb- like appearance (Plate 29, fig. 24). The comparison of a number of these struc- tures has convinced me that they are in truth hemioxyhexasters which have been soldered to the growing skeleton-net and the rays of which have been secondarily EURETE SPINOSUM. 137 thickened by the apposition of silica-layer, together with the beams of the skele- ton-net. which had, as it were, incorporated them. The rhabds, which may, as above mentioned, be foreign, are long, smooth centrotyles. They are about 15 m thick near the centre. The tyle measures about 17 m in transverse diameter. The superficial pentactines (Plate 29, figs. 20-22) usually have fairly equal, straight, conic, terminally rounded lateral rays, which enclose angles of 90° with their neighbours (Plate 29, fig. 20). Rarely (Plate 29, fig. 21) the lateral rays are cylindroconic, curved, and irregularly arranged. The lateral rays are 150- 270 m long, 12-22 ^ thick at the base, and covered throughout with vertically arising spines. The spines on the proximal part of these rays are 8-12 ^ long; distally they become smaller. The apical (proximal) ray is smaller than the lateral rays and destitute of large spines. The hemioxyhexasters (Plate 29, figs. 9-17, 26b) measure 80-122 ^ in total diameter, usually 90-110 n. Two of their rays, which extend in the same axis and lie opposite each other, are usually conic, short and simple, and only excep- tionally bear an end-ray. These two rays I designate the apical. The four other rays, which lie in a plane vertical to the axis of the other two, nearly always bear end-rays. These four rays I designate the lateral. The simple stems (main-rays) of these lateral rays always enclose angles of 90° with their neigh- bours and are, in the same spicule, usually fairly equal (Plate 29, fig. 10); only exceptionally they differ in length (Plate 29, fig. 12). In the ordinary regular hemioxyhexasters the lateral main-rays are 16-24 y long; in the rare irregular forms the shortest is sometimes only 14 ^ long, or still shorter. The lateral main-rays are cylindroconic, at the base 3. 5-6. 5 ^ thick, usually about 4 fx, and uniformly attenuated towards the end, the transverse diameter of which is about three quarters of that of the base. The thickness of these main-rays is not in proportion to their length, the thickest not being longer, often indeed shorter than the thinner ones. The lateral main-rays bear minute spines which decrease in size proximally. In the thinner ones these spines can only be made out in the distal part, and also here only in the u. v. photographs (Plate 29, fig. 9). The thick ones are covered with clearly visible spines throughout (Plate 29, fig. 12). Each lateral main-ray bears. three regularly disposed end-rays which lie in the plane of the four lateral main-rays. One of them extends in the same direc- tion as the main-ray to which it belongs, and appears as a continuation of the latter. The other two lie symmetrically on the two sides of this central one. These regularly disposed end-rays are, in the same spicule, usually equal (Plate 138 EURETE SPINOSUM. 29, fig. 10). In the few hemioxyhexasters, however, in which the main-rays are unequal, a corresponding irregularity is also observed in the end-rays (Plate 29, fig. 12). The regularly disposed end-rays are conic, sharp-pointed, and covered with minute, backwardly directed spines (Plate 29, fig. 14). In a few hemioxy- hexasters with exceptionally thick lateral main-rays the regularly disposed end- rays are reduced in length and terminally rounded. In the normal, regular hemioxyhexasters the end-rays are 25-44 n long, and 1.8-3. 7 ^ thick at the base. In the irregular forms the shortest are sometimes only 13 n long. The central end-ray of each group of three is straight throughout; the two lateral ones are either also straight throughout (Plate 29, fig. 12) or, much more frequently, straight only in their middle- and end-parts, but curved at the base, concave to the central end-ray. The chords of the lateral end-rays enclose angles of 47-52° with the central end-ray. Besides these regularly disposed end-rays other end- or branch-rays some- times arise from the lateral main-rays. Occasionally one or two supernumerary end-rays are added to the regularly disposed three. These additional end-rays extend, like the latter, in the plane of the lateral main-rays. More frequently a branch-ray is seen arising some distance below the end of the lateral main-rays. These branch-rays extend more or less vertically to the plane of the lateral main-rays, and are parallel to the apical rays. In size and spinulation the supernumerary end- and branch-rays are similar to the regularly disposed end- rays; they are, however, more frequently irregularly curved. The axis of each lateral main-ray is occupied by an axial thread (Plate 29, figs. 14-17, 19). This terminates at the end of the main-ray and does not send branches into the end-rays. The latter are destitute of axial threads. The scopuies (Plate 29, figs. 1-8, 26a) are 140-288 m long. They consist of a centrum, 3.8-7 n in diameter, usually 4-5 m, from one side of which arises a shaft, and from the other arise four or, rarely, five or six end-rays. The shaft is conic, straight, or slightly curved, 115-261 m long, and 1. 9-2.4 /x thick at the base. Near the distal end and often also near the base it bears minute spines. The end- rays diverge distally and together form a brush-like verticil 9-18 // broad at the end. The individual end-rays are very slightly curved, concave to the continua- tion of the shaft at the base, and nearly straight in their remaining part. They are 20-44 n long, 0.9-1. 5 m thick at the base, very slightly attenuated towards the end, and densely covered with minute, backwardly directed spines. At the end they bear a verticil of larger, recurved spines, which together form a kind of terminal disc with strongly serrated margin (Plate 29, figs. 7, 8). EURETID. 139 Although the specimen at my disposal is but a small fragment there can be little doubt that it belongs to the group of sponges represented by Eurete bower- bankii F. E. Schulze and Eurete marshalli F. E. Schulze1 2. Since, however, it differs from these species by its superficial pentactines, which are much more spiny than in either E. bowerbankii or E. marshalli , and since its hemioxyhexasters have relatively longer end-rays than those of E. botoerbankii 2 and relatively shorter end-rays than those of E. marshalli,3 it cannot be assigned to either of them and must be considered as a new species. Euretid from Station 4641. Plate 106, figs. 1-3. The supporting skeleton-nets of three euretids, one large fairly intact, and two small fragmentary ones, were trawled near Chatham Island, Galapagos, at Station 4641 on 7 November, 1904; 1° 34.4' S., 89° 30.2' W. ; depth 115 m. (633 f.); they grew on a light gray Globigerina ooze; the bottom-temperature was 39.5°. The larger supporting skeleton-net (Plate 106, fig. 3) is 47 mm. long and consists of a tube, 7 mm. wide, with nearly circular transverse section, which rises vertically from the base of attachment. This tube is straight for the greater part of its length, but bent abruptly to one side a little below its free upper end. Eighteen tubular branches, with a maximum length of 7 mm., and about as wide as the main-tube, arise from this tube. These branch-tubes are arranged in a spiral line. Some of them are distinctly widened distally, funnel-shaped. The basal part of the main-tube, and the lowest branch-tubes have walls about 2 mm. thick. Distally the walls become thinner, the uppermost being about 1 mm. thick. In the smaller specimens the main-tube is shorter and a little wider. The beams composing these skeleton-nets are, in the middle-part of the length of the main-tube of the largest specimen, mostly 40-80 m thick. The meshes of the network are, in the inner, gastral parts of the tube-walls, 100-300 /x wide and square with strongly rounded corners (Plate 106, fig. 1). In the outer, dermal parts of this portion of the skeleton-net the meshes are mostly 80-350 y. wide and more frequently triangular with rounded corners (Plate 106, fig. 2). The axes of the rays of the spicules, through the concrescence of which these 1 F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 297. 2 F. E. Schulze. Loc. cit., pi. 79, fig. 13. 3 F . E. Schulze. Loc. cit., pi. 79, fig. 3. 140 EURETID. skeleton-nets have been produced, are very distinct. In many places small hexactines, attached by the tip on one of their rays, arise vertically from the beams of the skeleton-net. I think there can be no doubt that these skeleton-nets belong to a euretid sponge, but since no loose spicules were found in them, I am unable to say to which genus they should be assigned. Euretid (?) from Station 4651. Plate 32, figs. 4-6. There are in the collection a fairly complete skeleton-net and three lamellar fragments of this sponge, all trawled off the coast of northern Peru, at Station 4651 on 11 November, 1904; 5° 41.7' S., 82° 59.7' W.; depth 4064 m. (2222 f.); they grew on sticky, fine, gray sand; the bottom-temperature was 35.4°. The fairly complete skeleton-net (Plate 32, fig. 4) consists of a dense basal mass with digitate processes, some of which are 10 mm. long and 6 mm. thick, from which arises a broad and low calyculate, funnel-shaped lamella. The margi- nal parts of the funnel are, for the most part, broken off. What remains of it is 65 mm. in maximum transverse diameter. Proximally, where it arises from the basal mass, the lamella forming the funnel is about 1.5 mm. thick. Towards the margin it thins out to 1 mm. The skeleton-net of the basal mass is very dense and irregular. Its beams are mostly 15-100 /x thick, and its meshes 15-220 /x wide. The small meshes are round, the large ones triangular or irregularly square. The outer (dermal) zone of the skeleton-net of the funnel (Plate 32, fig. 6) is irregular, composed of beams 20-180 /x thick, which enclose mostly triangular meshes up to 700 ,u wide. The inner, gastral zone (Plate 32, fig. 5) is more regular, but does not attain such a degree of regularity as is often observed in the corresponding zone of the skele- ton-nets of the Euretidae. It is chiefly composed of smooth longitudinal and transverse beams, but a fair number of usually spined, oblique beams also occur in it. The longitudinal beams are 50-100 /x thick, the transverse beams are sometimes 160 /x thick. The oblique beams are much thinner, usually only 15-30 ix thick. The meshes are square or, less frequently, triangular. The square ones are usually somewhat irregular, not rectangular, 600-900 /x long, and 190-550 m broad. These skeleton-nets, which are similar to the ones from Station 4695, proba- bly belonged to a euretid. EURETID. 141 Euretid (?) from Station 4685. There are in the collection three small, flat, lamellar fragments about 1 mm. thick, the largest of which is 16 mm. long, trawled in the southeastern Pacific at Station 4685 on 10 December, 1904; 21° 36.2' S., 94° 56' W.; depth 4033 m. (2205 f.); they grew on dark brown clay; the bottom-temperature was 35.3°. These lamellae are skeleton-nets composed on one face of longitudinal and transverse beams, mostly 40-50 m thick, which enclose square, rectangular meshes, generally 300-500 n long and 200-250 ^ broad; on the other face of considerably thinner beams, which enclose smaller, irregularly triangular meshes. The beams are mostly spined. The spinulation is more developed in the irregu- lar than in the regular part of the network. Numerous hexactines, 100-150 ^ or more in diameter, are attached by one ray to the beams of this network. These skeleton-nets probably belonged to a euretid. Euretid (?) from Station 4695. There are in the collection four fragments of skeleton-nets of this sponge trawled northeast of Eastern Island, at Station 4695 on 23 December, 1904; 25° 22.4' S., 107° 45' W. ; depth 3694 m. (2020 f.); they grew on fine, light brown ooze. The largest and least incomplete is 32 mm. high, and appears as a tubular stalk, extending above to a thin-walled funnel 22 mm. in diameter. The stalk is about 10 mm. long, and in the middle, where it is somewhat attenuated, of oval, transverse section, 6.5 mm. broad and 4.5 mm. thick. The skeleton-net of the stalk is irregular, composed of longitudinal and oblique spined beams, the former about 90 m thick, the latter 15-50 n. In places the stout longitudinal beams of this part of the net bear numerous, vertically arising thorns, 6-10 m thick at the base, and of varying length. The meshes of this network are irregular, generally 50-200 ^ wide. The skeleton-net of the funnel is more regular, chiefly composed of longitudinal and transverse beams. Oblique beams, however, also occur in it, particularly in its outer zone. The beams of this network are smooth and 50-130 m thick, the meshes in the inner zone square, rectangular, in the outer zone more frequently triangular. The rec- tangular meshes of the inner zone are mostly about 600 n long and 300-400 u broad. Verticil thorns, directed towards the funnel-cavity, arise from the nodes of the inner part of this network. 142 CHONELASMA. These skeleton-nets may have belonged to a euretid sponge. They are similar to those described above from Station 4651. COSCINOPORIDAE Zittel. Lamellar, calyculate, or more complicated Hexasterophora consisting, if lamellar, of a simple plate; if calyculate or more complicated, of a rather thin wall enclosing a wide cavity. This plate or wall is traversed by straight, conical, blindly ending, sac-shaped afferent and efferent canals. With a firm supporting reticulate skeleton and uncinates and scopules. The collection contains one specimen of this family, which belongs to a species of Chonelasma. CHONELASMA F. E. Schulze. Funnel-shaped or lamellar Coscinoporidae. Chonelasma sp. Plate 32, figs. 7-9. There is in the collection a rather large skeleton-net of this sponge, collected in the Paumotu Islands at Station 3689 (A. A. 134) on 28 October, 1899; 18° 06' S., 142° 24' W. ; depth 1476 m. (807 f.); they grew on a bottom of fine coral-sand and manganese nodules; the bottom-temperature was 37.6°. This skeleton-net (Plate 32, fig. 7) is a curved plate, 92 mm. long, 51 mm. broad, and 9-1 1 mm. thick. The sponge to which it belonged may have been tubular or calyculate; probably it was of large size. The convex, probably outer (dermal) zone of the skeleton-net (Plate 32, fig. 8) is on the whole smooth. It is composed of skeleton-net lamellae vertical to the surface, extending in- discriminately in all directions and crossing each other irregularly. These lamellae form a network, the meshes of which are represented by short vertical canals round or polygonal in transverse section and 0.5-2 mm. wide. The concave, probably inner (gastral) zone of the skeleton-net (Plate 32, figs. 7, 9) has some outgrowths. Most of these are quite small. One is 8 mm. high. Apart from a curved, obliquely transverse band 3-5 mm. broad, where the net- work is so dense as to appear nearly solid to the naked eye, the zone of the skeleton-net bordering on this inner concave, probably gastral surface is com- posed of skeleton-net lamellae, vertical to the surface and extending longitudi- nally. These lamellae are about 0.7 mm. apart and connected by numerous HEXACTINELLA. 143 transverse beams, which, to a certain extent, also form skeleton-net lamellae. These transverse lamellae are, however, not nearly so compact and so regularly arranged as the longitudinal ones. Together the longitudinal and the transverse skeleton-net lamellae form a network with meshes about 0.7 mm. broad and 0.7-1. 5 mm. long. The skeleton-net lamellae of the outer zone, that is the one bordering on the convex side (Plate 32, fig. 8), are composed of a network of beams mostly 450- 650 jx thick, which enclose roundish irregular meshes, usually 1.5-2. 5 mm. wide. The beams of this network are covered with large, rounded protuberances. Its meshes are either quite empty or contain only slight traces of a fine secondary network, similar to that in the inner zone, described below. The skeleton-net lamellae of the inner zone, that is those bordering on the concave side (Plate 32, fig. 9) , are composed of a primary network in the meshes of which a fine secondary network is spread out. The primary network consists of smooth, longitudinal, transverse, and oblique beams. The longitudinal beams are situated either singly or in bundles of two or three. Those of the same bundle are connected at frequent intervals by short transverse beams. Here and there they even coalesce to form irregular stems sometimes 350 p thick. The individual longi- tudinal beams are usually about 130 p thick, the transverse and oblique 60-110 p. The meshes are very irregular and are sometimes more than 1 mm. long. Thorns about 200 p long, 40 p thick at the base, and provided with low, rounded protu- berances arise from some of the nodes of this network. The secondary network extends in the meshes of the primary and in the transverse band above referred to, and also occupies the interstices between the lamellae. It is composed of beams, 5-10 p thick, which enclose square, rectangular, or, more rarely, irregular meshes 50-130 p wide. TRETOCALYCIDAE F. E. Schulze. Hexasterophora with ramified afferent and efferent canals. With a firm reticulate supporting skeleton and uncinates and generally also scopules. The collection contains one specimen and three fragments of this family, which belong to Plexactinella. HEXACTINELLA Carter. Tretocalycidae which are calyculate or composed of simple, ramified, or anastomosing tubes; with firm reticulate supporting skeleton, uncinates, scopules, 144 HEXACTINELLA MONTICULARIS. and discohexasters or oxyhexasters or tylehexasters or two of these forms. With- out microonychhexactines and tylostyles with slender branch-rays, bearing end- discs, on the tyle. The collection contains one specimen and three fragments of this genus. The specimen is insufficiently preserved for specific distinction. The three fragments all belong to a new species. Hexactinella monticularis, sp. nov. Plate 28, figs. 1-28. Three fragments of the skeleton of this sponge were trawled south of Chat- ham Island, Galapagos, at Station 4642 on 7 November, 1904; 1° 30.5' S., 89° 35' W. ; depth 549 m. (300 f.); they grew on broken Globigerina shells; the bottom-temperature was 48.6°. From the surface broad and truncate conic protuberances arise and to these the name refers. Shape and size. The three fragments measure 16, 17, and 20 mm. in maxi- mum diameter respectively. All appear to be parts of an irregular massive sponge with stout, truncate, conic protuberances. One of these protuberances, which is about 4 mm. high and 8 mm. broad at the base, is represented (Plate 28, figs. 23, 28). The colour in spirit is brown. The skeleton consists of an internal and superficial network and loose hexac- tines, pentactines, uncinates, discohexasters, and scopules. The internal skeleton-net (Plate 28, figs. 23, 24, 26, 28) forms meandric lamellae, mostly nearly 0.5 mm. thick, which appear as the walls of tubes, with lumina more or less circular in transverse section and about 1 mm. wide. In the interior of the sponge these tubes are variously curved and irregular in their course. On approaching the surface they straighten out. On the whole they extend chiefly radially and longitudinally from the base to the upper and lateral parts of the surface, where they open out. The openings are fairly equidistant and uniformly distributed, as numerous on the summits and the sides of the monticular processes as on the other parts of the surface. Since most of the tubes reach the surface obliquely their superficial openings are more or less oval (Plate 28, figs. 23, 28). It is to be presumed that the tubes form two systems, one afferent, vestibular (“Epirhysen”); the other efferent, preoscular (“Apo- rhysen”). HEXACTINELLA MONTICULARIS. 146 The lamellae separating these tubes consist of a network of beams, mostly 40-100 n thick, with meshes 100-200 ^ wide. Some parts of this network are quite irregular, others more regular, with more or less quadratic meshes. The beams generally bear small, broad, sharp-pointed, conic spines (Plate 28, fig. 22). Large, freely terminating, conic protuberances, which are hexactine rays and may be designated as thorns, arise from the beams in many places. In the inner part of the lamellae these thorns are not numerous; they are small, usually 90-200 n long (Plate 28, fig. 22). In their superficial part they are more numerous, more or less vertical to the surface of the lamella, and larger, 120-360 n long, and about 60 n thick at the base. These superficial thorns are covered with spines similar to those on the beams, but on the whole larger and more densely crowded. The superficial skeleton-net (Plate 28, figs. 21, 27), remnants of which have been found in several places, extends paratangentially on the surface. It is rather loose and irregular, and consists of pentactines the lateral rays of which have been more or less soldered together. The loose hexadines (Plate 28, figs. 17, 18) found in the interior are probably destined to be soldered together to form the internal skeleton-net. The small, probably young forms have straight, or slightly curved, nearly smooth rays, 70- 100 n long and 3 m thick at the base. In the larger, probably older ones (Plate 28, figs. 17, 18) the rays are 100-260 n and more long, nearly cylindrical, and 10-14 ix thick. They are, in the same spicule, often unequal and always covered with spines. Most of these spines are small, whilst some, which lie irregularly scattered between the small ones, attain a very large size and measure 10-50 n in length. These large spines, of which each ray bears from five to ten or more, increase in size towards the distal end of the ray. The largest of them bear small secondary spines. Several, usually three, are situated terminally. These are always the largest. The large spines along the length of the rays arise nearly vertically, the terminal ones usually point obliquely outward. The pentactines (Plate 28, figs. 19, 21, 27) are situated superficially. Their lateral rays, which form the superficial net, are 120-200 fx long, 4-10 n thick at the base, and slightly attenuated towards the end. They are covered throughout with vertically arising spines. Young, still free, superficial pentactines (Plate 28, fig. 19) have slender rays and very small spines. Older ones, already incor- porated in the superficial net (Plate 28, figs. 21, 27), have stouter rays and longer spines. Of uncinates two kinds, a smaller and a larger, can be distinguished. The smaller uncinates (Plate 28, fig. 10), which are very numerous and 146 HEXACTINELLA MONTICULARIS. doubtlessly proper to the sponge, attain a length of 225-420 n. They are centrotyle and anisoactine, the tyle, which marks the morphological centre, being situated much nearer the end from which the spines diverge than the other. The proportion between the length of the two actines is 2 : 3 to 1 : 3. Close to the tyle these uncinates are usually 2-3 /x thick, the tyle itself being about 0.7 more in transverse diameter than the adjacent parts of the spicule. The spines are numerous, very oblique, and so thin that it is impossible to see them with ordinary light. The u. v. photographs, however, show them clearly enough (Plate 28, fig. 10). I should say that these spines are scarcely thicker than 0.1 ii. The large uncinates are rare and may be foreign to the sponge. All those observed were broken. The largest fragments were 600-800 n long and about 5 m thick. Their spines are strongly inclined, nearly parallel to the shaft, and exceedingly thin. Two kinds of discohexasters, a larger and a smaller, can be distinguished. These are, it is true, connected by intermediate forms, but the latter are so rare that the distinction between them is quite clearly pronounced. The large discohexasters (Plate 28, figs. 12, 15, 16, 25) measure 52-62 /x in total diameter, usually about 60 and have equal and regularly arranged, fairly smooth main-rays, 5-6 n long and about 1.8 n thick. Each main-ray bears four rather strongly divergent end-rays. The end-rays are curved, concave to the continuation of the main-ray at the base, and straight or slightly curved in an irregular manner farther on. The end-rays are about 23 ^ long, 1.2-1. 3 m thick at the base, and attenuated distally to 0.7-1 ix. They bear along their whole length numerous minute, backwardly directed spines and at the end a verticil of larger, recurved spines, which together form a kind of convex terminal disc with strongly serrated margin, 1.5-2. 2 /x in transverse diameter (Plate 28, fig. 12). The small discohexasters (Plate 28, figs. 11, 20) measure 30-47 n in total diameter, and have equal, regularly arranged, fairly smooth main-rays, 4. 5-6. 5 /j. long and 1-1.6 /x thick. Each main-ray bears four, exceptionally five, end-rays. These are curved at the base, concave to the continuation of the main-ray, and nearly straight farther on. In these small discohexasters the basal curvature usually extends farther than in the large discohexasters. The end-rays are 9-18 m long, 0.5-1 /x thick at the base, and attenuated distally to 0.4-0. 7 /x. They are covered along their whole length with numerous minute, backwardly directed spines, and usually bear at the end a verticil of four or more larger recurved spines, which, when seen in profile, together appear as a convex terminal HEXACTINELLA MONTICULARIS. 147 disc, 1-2.5 m in transverse diameter (Plate 28, figs. 11, 20). Sometimes these spines are so small that the end-rays appear terminally rounded and destitute of terminal discs. The scopules (Plate 28, figs. 1-9, 13, 14) are 220-400 /x long. They consist, of a stout centrum, from one side of which arises a simple shaft, and from the opposite a verticil of end-rays. Sometimes one or two end-rays are also attached to the sides of the centrum. The centrum is 6. 2-9. 6 m broad, 4-9 n long, and has four lateral protuber- ances arranged regularly crossways. When small these protuberances appear as slight rounded elevations (Plate 28, figs. 7-9), when large as short, cylindrical, terminally rounded ray-rudiments, equaling the shaft in thickness (Plate 28, figs. 5, 6). The centrum and its protuberances are uniformly and densely covered with minute spines. ■ The shaft is 200-345 n long, straight or, rarely, curved. It is nearly cylindrical for the greater part of its length, and rather abruptly attenuated to a sharp point. It is 3-4.5 /x thick at the base, where it rises from the centrum; in the middle of its length it is slightly thinner, or, not so frequently, as thick or slightly thicker than basally. The middle-part of the shaft is nearly smooth. The proximal part, for a distance of about 30 n from the centrum, is, like the centrum, densely covered with minute spines. In a belt which is 10-20 /x broad and situated a short distance from the distal end, larger, particularly broader sparsely scattered spines occur. Of end-rays there are from five to nine, most frequently seven. As men- tioned above, these generally all rise from the apex of the centrum, that is the face opposite the shaft. These terminal end-rays are slightly curved, concave to the continuation of the axis of the shaft for a short distance, and, for the remainder of their length, straight or curved slightly in the opposite direction (outwards). They diverge above more or less and together form a stouter or more slender, brush-like or calyculate verticil, 9-22 n broad at the distal end. These end-rays are 1 1-65 m long, most frequently 1 1-30 /x. Of 33 measured : - 0 was under 10 m long. 1 was 36-40 M long 5 were 11-15 n C i 0 “ 41-45 M ( L 9 U 16-20 M u 1 “ 46-50 M a 7 u 21-25 M u 0 “ 51-55 M a 7 u 26-30 fx u 0 “ 56-60 M u 2 u 31-35 /x u 1 “ 61-65 M u 0 was over 66 n long 148 HEXACTINELLA MONTICULARTS. These end-rays are, at the base, 1-2 n thick, very rarely 2.6 n, and attenuated towards the distal end to 0.6-1 p, rarely 1.4 p. They are densely covered with minute, backwardly directed spines, and usually bear a terminal verticil of larger, recurved spines which together form a kind of convex terminal disc with deeply serrated margin, 1.2-2. 5 n in transverse diameter. Sometimes the termi- nal spines are so small that no disc-shaped terminal thickening at all can be detected. The exceptionally occurring lateral end-rays are more divergent, more curved, and shorter than the terminal ones above described, which they resemble in all other respects. From a point in the middle of the centrum six axial threads extend in three straight lines vertical to each other. One of these is long and well-developed. This one is continued in the axis of the shaft, which can be traced quite to the end of the latter. The other five axial threads are short, rudimentary, and terminate within the centrum. The one in line with and opposite the axis of the shaft is directed towards the terminal end-ray verticil, and ends before reaching it without giving off branches. The end-rays are destitute of axial threads. The other four axial threads terminate in the four lateral protuber- ances of the centrum. The shape of the scopules and the arrangement of their axial threads indi- cate:— that the upper part of the centrum, from which the end-ray verticil arises, is, as far as it is traversed by the axial thread, an end-ray bearing main- ray; that the shaft is a well-developed, simple ray; that the four lateral pro- tuberances of the centrum are rudimentary simple rays, and that the end-rays are homologous to hexaster end-rays. Thus the whole scopule appears as a hemihexaster. Since its end-rays bear the terminal verticils of recurved spines characteristic of the discohexasters and hemidiscohexasters, these scopule- hemihexasters are discohemihexasters. In view of this I think it not unlikely that the scopules of the Hexactinellida generally are to be considered as apically highly differentiated hemihexasters, the scopules of the sponge here described being not quite so far advanced in this development and not so far removed from the ancestral form as the scopules destitute of lateral protuberances of the centrum of other hexactinellids. The comparability of the scopules with hexasters was first noticed by F. E. Schulze who says1 concerning their end-rays, “I should be more inclined to compare them with the terminal rays of the rosettes.” But this author does not 1 F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 34. HEXACTINELLA. 149 draw the same conclusion as I should concerning their origin from this com- parability and their general structure, and expresses 1 his inclination to consider them “as diacts or monacts.” In spite of the fragmentary condition of the specimens they can, with a sufficient degree of certainty, be assigned to Hexactinella. Of all the known species only two, H. ventilabrum Carter and H. labyrinthica Wilson, have, like them, discohexastrose microscleres. From both of these species the sponge above described differs by the scopules, which have four end-rays in the former, and usually seven end-rays in the latter. Hexactinella sp. indet. Plate 32, figs. 13-15. A skeleton-net probably a species of Hexactinella was trawled off the south- ern coast of western Panama at Station 4631, on 3 November, 1904; 6° 26' N., 81° 49' W. ; depth 1415 m. (774 f.); they grew on a bottom of green sand; the bottom-temperature was 38°. This skeleton-net (Plate 32, fig. 13) has the shape of a funnel 30 mm. high and 52 mm. in maximum breadth above. The funnel-wall is 4 mm. thick. Both the upper marginal part and the lower end, which latter may have been attached to a stalk, are broken off. The funnel-wall consists of skeleton-net lamellae extending radially and longitudinally from the base towards the margin. These lamellae are mostly a little over 1 mm. apart and joined to each other by groups of oblique beams, which, on the inner side of the funnel, form a honey- comb-like net (Plate 32, fig. 15) composed of lamellae vertical to the surface and enclosing short, likewise vertical canals, round or polygonal in transverse section, and mostly 1.5-2. 5 mm. wide. The skeleton-net of these lamellae consists of smooth beams, on an average about 100 p thick, which in some places extend longitudinally and transversely with rather large square, rectangular meshes, but which are generally, particu- larly in the inner honeycomb zone, so variable in their direction, so crowded, and joined at so frequent intervals, that they form a quite irregular and very dense network. 1 F. E. Schulze. Loc. cit., p. 35. 150 HYALONEMA. Amphidiscophora F. E. Schulze. Hexactinellida the spicules of which are always isolated; with amphidiscs; without hexasters. Of the two families into which F. E. Schulze1 divides this suborder, one, the Hyalonematidae, is represented in the collection. HYALONEMATIDAE (Gray) F. E. Schulze. Amphidiscophora in which the afferent apertures all lie in one area, the gastral face. The collection contains fifty-seven more or less complete specimens and six fragments of this family. All belong to the genus Hyalonema. HYALONEMA Gray. Hyalonematidae with gastral cone, without conuli-like protuberances on the dermal face; with one or, exceptionally, several stalks composed of long intertwined anchoring spicules; with acanthophores in the lower end-part of the body. Two specimens cannot be specifically determined. The other fifty-five, and the six fragments, belong to twenty-four species, twenty-two of which are new. Hitherto fifty well-defined species of Hyalonema have been described. To these twenty-two are added in this Report, so that there are now seventy-two valid species of Hyalonema. The number of species being so great I en- deavoured to arrange them in subgenera. In attempting to do this I first thought it might be possible to fall back on F. E. Schulze’s 2 original division of the genus into the subgenera Hyalonema (with a special gastral sieve-mem- brane) and Stylocalyx without such a structure. I found, however, as Schulze himself did on reconsideration,3 that this could hardly be done with advantage. Then I tried to attain my object with the help of the key given in Schulze’s Valdivia report,4 but this also helped me only to a small extent. I therefore 1 F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4, p. 181. 2 F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 189. 3 F. E. Schulze. Revision des systemes der Hyalonematiden. Sitzungsb. Akad. Berlin, 1893, no. 30, p. 554. 4 F. E. Schulze. Hexactinellida. Ergeb, Deutsch. tiefsee-exped., 1904, 4, p. 163. HYALONEMA. 151 propose a new arrangement, based on the results of my examination of the twenty-four Pacific species. These results have led me to think that certain characters of the amphi- discs could be utilised for this purpose. It is true that the numerous very differ- ent forms of these spicules are to a great extent connected by transitions ; there are, however, in spite of this, some amphidisc-forms not so connected. The anchor-teeth of the amphidiscs of most of the Pacific Hexactinellida have smooth margins. In five of them, however, there occurs a particular kind of amphidiscs with serrated anclior-teeth. For these I establish the subgenus Prionema. Of the fifty species previously known there are, I believe, only two, II. poculum F. E. Schulze 1 and H. validum F. E. Schulze,2 in which amphidiscs with serrated teeth have been noticed and described. I think it highly probable, however, that such amphidiscs occur in others also, as for instance in H. lusita- nicum Bocage, and H. cupressiferum F. E. Schulze, where they have not been mentioned either because they were overlooked — they are generally small and clearly visible only with high powers — or because the authors who studied these sponges did not consider them of importance. Most of the species of Hyalonema examined by me in which the anchor- teeth of all the amphidisc forms are smooth-margined, generally have hyper- bolic, semispherical, or bell-shaped anchors and measure from about a quarter to a third of the whole spicule in length. In some of them, however, the amphi- disc-anchors are of other relative dimensions and often also of another shape. In five of the Pacific species examined, one of which had been previously de- scribed, the anchors of a certain kind of amphidiscs are more or less semi- spherical and about half as long as the whole spicule, so that the two anchors of the same spicule nearly or quite meet in the middle. For these species I establish the subgenus Oonema. Of the species previously described there are, besides the one in the A. Agassiz Pacific collection above referred to, four ( H . tenerum F. E. Schulze, H. robuslum F. E. Schulze, H. globiferum F. E. Schulze, and II. pedunculcitum Wilson) which can certainly, and one ( H . ovuliferum F. E. Schulze) which can perhaps, be assigned to this subgenus. In two of the Pacific species examined by me, one of which had been previ- ously described, the anchors of the largest amphidiscs are small and relatively very short and broad. For these species I establish the subgenus Phialonema. 1 F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 208. (This serration is not shown in the figure of a macramphidisc of this species. Loc. cit., plate 33, fig. 4). 2 F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4, p. 82, taf. 34, fig. 8. 152 HYALONEMA. Of the species hitherto described there is, besides the one reexamined by me which is referred to above, one ( II . pellucidum Ijima) at least, probably several, which can be referred to this subgenus. In two of the Pacific species examined one kind of amphidisc has broad and rather low, umbrella-like amphidisc-anchors. For these I establish the sub- genus Skianema. In one of the Pacific species examined I found a peculiar kind of amphidisc with from one to three branches on the convex side of some or most of its anchor- teeth, which give to the anchors the appearance of being doubled. For this species I establish the subgenus Thallonema. The remaining species of Hyalonema, in which none of the different kinds of peculiar amphidiscs referred to above occurs, can be divided, in accordance with the primary division used in F. E. Schulze’s key, into those in which the largest amphidiscs are stout and have a thick shaft; subgenus Hyalonema, and into those in which these amphidiscs are slender and have a thin shaft; subgenus Leptonema. Nine of the Pacific species examined by me, two of which were insufficient for exact description and for naming, and the great majority of the species of Hyalonema previously described, belong to the subgenus Hyalonema. One of the Pacific species examined by me, and at least five previously described species ( H . poculum F. E. Schulze, II. solutum F. E. Schulze, H. urna F. E. Schulze, H. divergent, F. E. Schulze, H. depressum F. E. Schulze) belong to the subgenus Leptonema. Possibly //. lusitanicum Bocage and II. cupressiferum F. E. Schulze men- tioned above as probably belonging to the subgenus Prionema, and H. ovuliferum F. E. Schulze assigned to the subgenus Oonema may also belong to the subgenus Leptonema. HYALONEMA (Gray) Lendenfeld. Species, the amphidiscs of which have hyperbolical, semispherical, or bell- shaped terminal anchors from about one fourth to one third of the whole spicule in length; without amphidiscs of any other kind. The largest amphidiscs are stout and have a thick shaft. The collection contains twenty-three more or less complete specimens and three fragments of this subgenus. Two of the specimens, apparently represent- ing two distinct forms, could not be specifically determined; the twenty-one others and the three fragments belong to seven different species, all of which are new. HYALONEMA (HYALONEMA) OBTUSUM. 153 Hyalonema (Hyalonema) obtusum, sp. nov. gracilis, var. nov. Plate 33, figs. 1-24; Plate 34, figs. 1-19; Plate 35, figs. 1-37; Plate 36, figs. 1-45; Plate 37, figs. 1-22; Plate 38, figs. 1-8; Plate 39, figs. 1-10. robusta, var. nov. Plate 39, figs. 11-41; Plate 40, figs. 1-22. Two specimens were trawled at two stations in the Tropical Pacific; - Hyalonema (H.) obtusum var. robusta at Station 3681 (A. A. 2) on 27 August, 1899; 28° 23' N., 126° 57' W. ; depth 4330 m. (2368 f.) ; it grew on light brown volcanic ooze; the bottom-temperature was 34.6°. H. (H.) o. var. gracilis at Station 3684 (A. A. 17) on 10 September, 1899; 0.50' N., 137° 54' W. ; depth 4504 m. (2463 f.) ; it grew on light yellow-gray Globigerina ooze. These sponges are distinguished from their nearest allies by the stout truncate or terminally rounded spines on their macramphidisc-shafts. To these the name refers. Although on the whole very similar in their spiculation, these two sponges differ in respect to their external appearance and certain characters of their skeletal element so that I consider them distinct varieties. The spicules of the specimen from Station 3681 (A. A. 2) are generally speaking stouter, those from Station 3684 more slender. 1 therefore name the former H. (II.) o. var. robusta, and the latter H. (II.) o. var. gracilis. Shape and size. The specimen of var. robusta is rather fragmentary, its super- ficial parts having to a great extent been lost. It consists (Plate 39, fig. 33) of a flattened body, 65 mm. long, 12 mm. thick, and 42 nun. broad above. Below it becomes narrower, and there protrudes from its rounded lower end a bundle of stalk-spicules. This bundle, where it arises from the sponge-body, is about 2.6 mm. thick. The stalk-spicules forming it are broken off at a distance of 35 mm. from the lower end of the sponge. The specimen of var. gracilis is well-preserved, but destitute of the stalk; the sponge-body having apparently been pulled off the stalk-spicules by the trawl. It has the shape of a short and broad spindle or top (Plate 33, fig. 15), is 47 mm. long (high), and has a maximum transverse diameter of 30 mm. The lower end, from which in life the large stalk-spicules arose, is now simply rounded off. The upper end consists of a gastral cone closely enveloped by the thin, frill-like margin of the wall surrounding the gastral cavity. The cone (Plate 33, fig. 16a) is 9 mm. high, nearly cylindrical, circular in transverse section, terminally rounded, 6 mm. thick at the base, and 4 mm. at the end. Its end is slightly 154 HYALONEMA (HYALONEMA) OBTUSUM. bent to one side (Plate 34, fig. 3c). The frill surrounding it terminates with a fairly circular margin which lies in the level of the summit of the cone. The gastral cavity appears as a narrow fissure 5-12 mm. deep but only 0.4-1 mm. wide (Plate 33, fig. 16; Plate 34, fig. 3b) separating the gastral cone from the marginal part of the sponge-body. The surface of the cone, and the inner face of the upper tubular marginal part of the wall surrounding the gastral cavity are smooth and destitute of aper- tures of any kind, the efferent openings being restricted to the bottom of the fissure-like gastral cavity. The intact parts of the outer surface exhibit a fine reticulate structure with meshes about 0.7 mm. wide (Plate 33, fig. 15). The colour of the specimen of var. robusta in spirit is rather dark reddish brown, that of var. gracilis light greenish brown. Canal-system. The state of preservation of the specimen of var. robusta renders it impossible to say anything about the canal-system. In the specimen of var. gracilis subdermal cavities (Plate 34, figs, lb, 3, 4, 19c), mostly 0.3-0. 7 mm. high and 0.2-0. 5 mm. broad, are spread out below the dermal membrane (the outer surface). These cavities are generally separated from each other by thin partitions. From most of them small afferent canals take their origin; some are directly continued in large afferent canal-stems, 0.3-0. 7 mm. wide, which extend somewhat tortuously towards the interior, and ramify in the central part of the sponge. Occasionally junctions of two such afferent canal- stems have been observed. The choanosome, that is the region occupied by the flagellate chambers, does not extend, for the most part, beyond the level of the floors of the subdermal cavities. In a few places only broad, conical groups of flagellate chambers rise between adjacent subdermal cavities, up to a distance of only 0.1 mm. from the outer surface. The individual flagellate chambers appear to be broad oval or nearly spherical, and attain a maximum diameter' of 60-100 m (Plate 34, fig. 2). The efferent canals join to form canal-stems up to 1.2 mm. wide, which, as above mentioned, open out into the bottom of the narrow, fissure-like gastral cavity. The larger of these canals are considerably contracted at the mouth. The skeleton of var. gracilis. The outer surface is covered with dermal pinules, micramphidiscs, and small macramphidiscs. Most of the pinules are pentactine, some hexactine. Their paratangentially extending lateral rays lie in the dermal membrane; their radially extending and freely protruding distal rays form a fur about 150 m high (Plate 35, fig. 24). The micramphidiscs are, in some places at least, exceedingly numerous. They seem to be quite HYALONEMA (HYALONEMA) OBTUSUM. 155 irregularly situated. The small macrampliidiscs are also numerous and often arranged in groups (Plate 34, figs. 1, 19b; Plate 35, fig. 24b). Their shafts ex- tend radially or obliquely and their distal parts protrude freely beyond the surface. The dermal membrane is supported by hypodermal pentac tines very variable in size. In the upper parts of the sponge the large pentactines greatly predominate, at the base the small ones are more numerous. The centres of the large hypodermal pentactines are about 0.7 mm. apart. The apical rays of these spicules are directed radially inward (Plate 34, fig. lc); their lateral rays, which are markedly inclined towards the apical ray, extend nearly paratangen- tially in the beams of the superficial network above referred to. Uncinate amphioxes, situated for the most part radially or obliquely, are met with in the subdermal region. The superficial part of the choanosome underlying the dermal surface is occupied, down to a depth of about 2.5 mm., by hexactine megascleres, rather regularly arranged in several paratangentially extending layers. These hexactines are situated so that two of their rays extend radially (inwards and outwards), two longitudinally (upwards and downwards), and two transversely (to the right and left). The distance between the centres of these spicules is less than the length of their rays, and the opposite rays of adjacent ones usually extend for some distance side by side and close together (Plate 34, fig. 19d). These hexactine megascleres, therefore, form a three-dimensional network with fairly regular, somewhat cubic meshes. These spicules vary greatly in size ; the larger are situated proximally, the smaller distally. Numerous rhabd-megascleres and a few angularly bent diactines of similar dimensions occur in the choanosome. Most of the rhabds are blunt amphioxes or amphistrongyles, but styles and tylostyles also occur. Some of these rhabds are isolated; most of them, however, form loose strands. In the central (axial) part of the choanosome, the rhabds extend for the most part longitudinally; in the other parts of the choanosome they are mostly directed obliquely upwards and outwards, and generally lie in the walls of the canals. The styles and tylo- styles are situated so that their rounded (thickened) end points downward and inward, their pointed end upward and outward. The choanosome is rich in microscleres. Large numbers of micramphidiscs are imbedded in the canal-walls and throughout it are scattered some macramphidiscs, masses of microhexac- tines (Plate 34, fig. 2), and a few microhexactine-derivates, chiefly with only two opposite rays fully developed and the others more or less, sometimes entirely reduced. 156 HYALONEMA (HYALONEMA) OBTUSUM. As above stated the sponge-body was in life obviously attached to a bundle of stalk-spicules, which have, however, been pulled out of it. Empty tubular spaces, sometimes 0.9 mm. wide (Plate 36, fig. 26a), the walls of which are formed by fine, highly stainable membranes, mark the places where the upper ends of the largest of these stalk-spicules were situated. These spaces lie in the axial part of the sponge-body. They are conical, attenuated above, and extend upwards to within a distance of 2 mm. from the summit of the gastral cone. In the lower part of the sponge-body these spaces are surrounded by a kind of cement, composed of dense masses of stout, one- to five-rayed, most frequently tetractine or diactine acanthophores (Plate 36, fig. 26). In this cement a few microhexactine-derivate pachyinicrohexactin.es also occur. Quite at the bottom, a short distance below the dermal membrane, numerous slender-rayed spicules with long spines, which I consider as slender acanthophores, form a kind of felt. These spicules are mostly tetractines, but a good many triactines and a few diactines, pentactines, and hexactines also occur among them. Transi- tional forms, connecting these spicules on the one hand with the stout acantho- phores above referred to, and on the other with the dermal pinules, are also found in this part of the sponge. The thin marginal part of the circular wall which surrounds the gastral cavity, and forms the boundary between the dermal and the gastral parts of the surface, contains numerous, longitudinally situated, diactine pinules, the distal rays of which protrude freely beyond the surface. The gastral surface, that is the surface of the gastral cone, and the inner surface of the wall surrounding the fissure-like gastral cavity are covered with micramphidiscs and gastral pinules. The micramphidiscs are situated irregu- larly, and in some places are so numerous as to form dense masses. The gastral micramphidisc-layer does not terminate at the openings of the efferent canal- stems into the gastral cavity, but is continued in the walls of these canals and their branches quite down into the innermost parts of the choanosome. The gastral pinules are mostly pentactine, but hexactine forms also occur. Their centres are 30-100 i± apart. Their lateral rays extend paratangentially in the gastral membrane; their distal apical rays arise vertically from the surface, and protrude freely beyond it, forming a dense fur about 125 m high (Plate 35, figs. 1, 3, 16). This pinule-fur is not, like the micramphidisc-layer, continued down the efferent canals, but terminates at their mouths. Small hypogastral pentactines, similar in position to the hypodermal pen- tactines above referred to, occur below the surface of the cone. HYALONEMA (HYALONEMA) OBTUSUM. 157 Strands of longitudinal rhabds enter the wall of the gastral cavity and the gastral cone from below. The rhabds of the gastral wall for the most part follow the gastral membrane, and here form a dense and distinct subgastral layer. The rhabds of the cone lie partly superficially, partly axially. The superficial rhabds of the cone are more slender than the axial ones. The axial rhabds are congregated in strands which together form a loose column extending quite to the summit of the cone (Plate 34, fig. 3). A few hexactine megascleres apparently with long longitudinal and shorter transverse rays also take part in the formation of this column. The micramphidiscs not only form a dense layer on the outer surface of the gastral cone, but also extend for some distance into its interior. Farther down, at a level about 0.3 mm. below the surface, micro- hexactines and microhexactine-derivates, similar to those of the choanosome, make their appearance in the cone. These spicules extend down to a depth of about 0.8 mm., thus occupying a zone about 0.5 mm. thick. The microhexac- tines are very numerous in this zone, the microhexactine-derivates rare. The central part of the cone, in which the axial column of longitudinal rhabds ex- tends, is destitute of microscleres. The skeleton of var. robusta appears to be on the whole similar. The micro- hexactine-derivates are more various; the uncinates attain a larger size, and reach down to greater depths of the sponge. The upper ends of the large stalk-spicules are still present, and the felt formed by the slender acanthophores in the basal part of the sponge-body is denser and more extensive (Plate 39, figs. 22-24). The dermal pinules (Plate 35, figs. 23, 24a, 25, 29-37; Plate 40, figs. 4, 5) are mostly pentactine, but hexactine forms also occur, differing from the pentac- tine ones only by possessing a sixth, proximal, apical ray. The distal apical ray is generally straight, rarely angularly bent below the middle of its length (Plate 35, fig. 25). In the dermal pinules of var. gracilis 137-165 n, the ray is usually 143-154 n long and 4-5 n thick at the base. Farther up it thickens and it gener- ally terminates with a stout, broad, and blunt cone 8-11 /x thick. Rarely it is terminally rounded, dome-shaped, and has a maximum thickness of 12 /x (Plate 35, fig. 31). The proximal part and the terminal cone (or dome) of the distal ray are smooth, its middle-part bears sharp, conic spines. The lowest of these spines are sparse, short, and strongly divergent. Farther up they become more numerous. The size of the spines increases up to the middle of the length of the distal ray and then again decreases; the inclination of the spines towards the tip of the ray increases continuously quite to the end. The largest spines attain a length of 13-19 /x, and are 2-4 n thick at the base, usually about 3.5 tx. The 158 HYALONEMA (HYALONEMA) OBTUSUM. maximum transverse diameter of the distal ray, together with the spines is 18-32 ix. The distal ray of the dermal pinules of var. robusta is 140-172 ix long and 5-8 /x thick at the base. The maximum transverse diameter of this ray, together with its spines, is 25-40 ix. The proximal apical ray, of the hexactine forms of var. gracilis, (Plate 35, figs. 29, 30) is straight, 10-42 \x long, and 3. 7-4. 5 \x thick at the base. It is cylindroconic, generally abruptly and sharply pointed, and covered with minute spines. The four lateral rays of the same spicule are usually fairly equal, the greatest difference of length observed not exceeding 4 /x. The lateral rays are straight; in the dermal spinules of var. gracilis they are 20-40 ix long, rarely up to 50 n, and 3-5 m thick at the base; in those of var. robusta they are sometimes (Plate 40, fig. 4) much shorter, 10-36 ix long. They are cylindroconic, rounded or, more rarely, abruptly pointed, and covered with minute spines. The gastral pinules (Plate 35, figs, la, 2, 3a, 4-9, 16; Plate 40, fig. 3) are, like the dermal pinules, mostly pentactine; hexactine forms, however, also occur dif- fering from the pentactine only by possessing a sixth apical proximal ray. The distal ray is straight; in the gastral pinules of var. gracilis, it is 73-145 /x long, usually 77-135 /x, and 4. 5-5. 5 ix thick at the base, in the gastral pinules of var. robusta 94-140 ix long and 5-7 ix thick at the base. It is thickened above, and attains its greatest thickness a little way beyond the middle of its length; then it again becomes thinner, and it ends in a usually sharp-pointed, rather slender, terminal cone, which does not exceed the proximal end of the ray in thickness. The proximal end-part and the distal cone of the ray are smooth ; its middle-part bears spines. The spines on the proximal half of the distal ray are very sparse, point obliquely upward, and are strongly divergent, the angles enclosed between them and the ray being 40°-55°. The spines on the distal half of the ray are smaller, more crowded, and less divergent, their size decreasing and their inclina- tion increasing towards the end of the ray. They attain a length of 15-25 m and a basal thickness of 3-4.5 ix. The maximum transverse diameter of the distal ray, together with the spines, is in both varieties 26-45 /x. The proximal ray (of the hexactine forms) (Plate 35, fig. 4; Plate 40, fig. 3) is straight, 43-74 /x long, 4. 5-5.5 m thick at the base, conical, pointed, and spiny. The four lateral rays of the same spicule are fairly equal or rather unequal in size; the maximum difference observed in their length was 15 /x- The lateral rays are straight or, more rarely, slightly curved. Their length is subject to considerable variation. They are in the gastral pinules of var. gracilis 35-90 /x HYALONEMA (HYALONEMA) OBTUSUM. 159 long, usually 45-70 ju, at the base 4. 5-5. 5 m thick, rarely as much as 6 n, conic, pointed or, more rarely, rounded at the end, and covered with spines, which are more conspicuous in the distal than in the proximal portion of the rays. In the gastral pinules of var. robusta the lateral rays are on an average somewhat longer, they measure here 47-75 m in length. The marginal pinules (Plate 35, figs. 10-13, 26-28) have been found only in var. gracilis; in the specimen of var. robusta they appear to have been lost. In these pinules only the distal and proximal rays are properly developed, the lat- eral rays being altogether rudimentary, and together forming merely a tyle. These spicules consequently appear as centrotyle diactines. The outer, distal one of their two properly developed rays, which corresponds to the distal apical ray of the hexactine and pentactine pinules, is 304-360 n long, rarely as much as 450 id, fairly straight, and 5-10 ^ thick at the base. Its proximal part, and its distal, conic, sharp-pointed end-part, are smooth. Its middle-part bears spines, which are rather strongly inclined towards the end of the ray, attain 6-10 n in length, and are 1.5-2 ^ thick at the base. The maximum transverse diameter of this ray, together with the spines, is 17-20 id. The opposite, inner, proximal one of their two properly developed rays, which corresponds to the proximal apical ray of the hexactine pinules, is usually 490- 665 id long, fairly straight, at the base about as thick as the distal ray, and attenuated towards the end. Sometimes it is greatly reduced in length, only 50 /d long, cylindrical, and thickened at the end to a terminal tyle 13 m in diameter. The central tyle, which is all there is left of the reduced lateral rays, is 3-7 n thicker than the adjacent parts of the spicules, and measures 8-15 ^ in transverse diameter. The hypodermal pentactines of the outer surface (Plate 33, figs. 5-14, 17, 24; Plate 34, fig. lc; Plate 39, figs. 31, 32, 40, 41). The proximal apical ray is straight or, rarely, slightly curved, and usually properly developed, conic, and blunt-pointed, occasionally reduced, cylindrical, and terminally thickened (Plate 34, fig. lc). It is in the large hypodermal pentactines, which greatly pre- dominate in the upper parts of the specimen of var. gracilis, when properly de- veloped, 0.7-1.86 mm. long and, at the base, 30-75 n thick, rarely 90 id. When reduced it retains its thickness throughout, but is less than half as long. In the small hypodermal pentactines, which occur chiefly in the lower part of this sponge, the proximal ray measures 0.27-0.6 mm. by 10-23 n. The lateral rays are inclined towards the proximal rgy, and enclose with it angles of 73°-84°. The four lateral rays of the same spicule are usually very unequal in length; the 160 HYALONEMA (HYALONEMA) OBTUSUM. longest is sometimes more than twice as long as the shortest. The greatest difference in length between the lateral rays of the same hypodermal pentactine observed was 310 /x. The lateral rays are straight, conic, and blunt. They are, in the large hypodermal pentactines of var. gracilis, 240-730 /x long and 32-60 /x thick at the base. In the small ones they measure 135-440 n in length. The small hypodermal pentactines accordingly have, relative to the proximal ray, considerably longer lateral rays than the large ones. At the end the lateral rays are usually from one fifth to one third as thick as at the base, and here measure 5-22 n in transverse diameter. The hypodermal pentactines of var. robusta have a proximal ray 0.47-1.3 mm. long, and 40-80 m thick at the base. The lateral rays are on the whole attenuated towards the distal end less than in the hypodermal pentactines of var. gracilis. They are, when not reduced, 250-750 /x long and, at the base, about as thick as the proximal ray. The end-parts of the lateral rays of these spicules exhibit remarkable irregu- larities of external shape and internal structure. These irregularities are the more conspicuous the thicker (the more blunt) the rays. Such an irregular lateral ray-end of a hypodermal pentactine of var. gracilis is represented (Plate 33, fig. 17). A rudiment of a branch-ray, arising a short distance from the tip of the main-ray, and a marked irregularity in the axial thread and the stratifi- cation of the siliceous body of the latter are noticeable in this spicule. I am inclined to ascribe these irregularities to the influence of the obstacles — other spicules — met by these rays during their longitudinal growth. The cells building the tips of these rays were forced to act in an abnormal manner; being prevented by other spicules from adding to the length of the axial thread and from depositing silica around it in a normal and regular manner, they produced the irregular structures observed. The obstacles (other spicules) which thus cause these irregularities are probably the stout proximal rays of adjacent hypodermal pentactines. The hypogastral pentactines of the gastral cone of var. gracilis have straight proximal apical rays, usually 240-400 /x long, and about 12-20 n thick at the base. The lateral rays are slightly inclined towards the proximal ray, straight, and generally 180-250 ^ long. In the specimen of var. robusta the parts contain- ing these spicules appear to have been lost. The hexactine megascleres of the distal part of the choanosome (Plate 34, figs. 5-18, 19d) are in both varieties very variable in size and have a maximum diameter of 350 n~ 2 mm. The rays of the same spicule are often unequal. The greatest difference of length observed in them was 400 n. The rays are 130-950 n HYALONEMA (HYALONEMA) OBTUSUM. 161 long, straight, conic, rather blunt-pointed, and 7-35 /x thick at the base. Their basal thickness is roughly speaking in proportion to their length. Very young stages of these hexactines appear as spheres, 20 /x in diameter, perforated by six axial cylinder threads, 5 /x thick, which are joined at right angles in the centre. Where these axial cylinder threads reach the surface of the sphere this is elevated in the shape of very thin-walled tubes rising about 10 n over the surface of the sphere (Plate 39, fig. 5). The hexactine megascleres of the loose axial spicular column , which were found only in var. gracilis, appear to be larger than the more superficially situated, but since I have not been able to find any intact ones, I can only say that their longitudinally extending rays appear to be much longer than their transverse rays, and that their rays are, at the base, about 40 m thick. The stout acanthophores (Plate 36, figs. 1-25, 27-45; Plate 39, figs. 17-21, 34-38) of the basal part of the sponge-body range from pentactine to monactine. The pentactines are rare. The few observed in var. gracilis were 225-530 n in diameter, and had rays, at the base, 12-29 m thick. The tetractines (Plate 36, figs. 1-25, 27, 28; Plate 39, figs. 18-20) generally have more or less unequal rays. The inequality of the rays is often very con- siderable. The rays are exceedingly variable in size, curvature, shape, and spinulation, but constant and uniform in so far as their basal parts always form a fairly regular, rectangular cross, and as the rays themselves always appear to extend nearly in one plane. The tips of the rays are nearly always more or less spiny, only quite exceptionally (Plate 39, fig. 20) entirely smooth. In both varieties these spicules measure 180-840 /x in to till diameter. Among the irregu- lar ones all sizes between these limits are met. The regular ones never appear to exceed 500 m in diameter. The rays are generally wavy in outline, cylindro- conical or cylindrical, and distally thickened, or, more rarely, without a thick- ening at or near the end (Plate 36, fig. 1; Plate 39, fig. 20). The ray either terminates with the distal thickening and then appears simply rounded off at the end (Plate 36, figs. 22, 23, 25; Plate 39, fig. 18), or it is continued beyond the distal thickening in the shape of a terminal cone (Plate 36, fig. 7). The rays of these spicules are in var. gracilis 35-380 ^ long and 12-35 n thick at the base; in var. robusta, where they are more irregular and stouter, 40-500 /x long and, at the base, 20-50 m thick. The distal thickening is in the tetractines of var. gracilis 10-40 n in diameter, in those of var. robusta 10-60 n. The thickness of the rays is not in proportion to their length, and varies in the rays of all lengths between similar limits. We consequently find among the 162 HYALONEMA (HYALONEMA) OBTUSUM. short rays relatively much stouter ones than among the long rays. The rays most strongly reduced, that is those under 55 m in length, are by far the relatively stoutest. None of the rays as short as this was in gracilis under 25 ' n, several of them were here 35 m thick. In both varieties the tips of the rays bear broad, conic, vertical spines with a maximum length of 4 /x (Plate 36, figs. 27, 28). On the distal thickening these spines are usually densely crowded (Plate 36, figs. 6, 7, 9), more rarely sparsely scattered (Plate 36, fig. 4, fig. 18, the upper and lower ray, fig. 23, the upper and left ray). They are usually confined to the distal thickening, the proximal part of the ray and the conic tip (when present) protruding beyond it being quite smooth (Plate 36, figs. 1, 2, 4-25, 27, 28). Sometimes, however, the spines cover the whole ray (Plate 36, fig. 3) in greater or smaller numbers. It is to be noted that the axial thread is in many of these tetractines, particu- larly in the slender-rayed (perhaps young) ones, remarkably wide (Plate 36, fig. 27), sometimes as much as half as thick as the ray itself. The triactines (Plate 39, fig. 21) are obviously tetractine-derivates, in which one of the rays has quite disappeared. They are more frequent in var. robusta than in var. gracilis, measure in both 330-760 n in total length, and have rays about 37-42 n thick in the former, and about 20 ^ thick in the latter. The diactine and monactine rhabds are of two kinds : — shorter and stouter tetractine-derivates, and longer and more slender derivates of the ordinary rhabds of the choanosome. The tetractine-derivate rhabds of the cement-mantles (Plate 36, figs. 31, 40-45; Plate 39, figs. 17, 34-38) are generally diactine and slightly and irregu- larly curved, rarely (Plate 39, fig. 17) strongly angularly bent. Such strongly bent, compass-like spicules have only been found in var. robusta. In var. gracilis some small spicules, also apparently belonging to this group, have been observed, in which the curvature is so great that one half of the spicule forms a complete circle (Plate 36, fig. 45). The tetractine-derivate rhabds in var. gracilis are 170-950 m long and 11-39 m thick near the middle; in var. robusta 450 ju-1-42 mm. long and 6-50 m thick near the middle. In the shorter spicules of this kind a central tyle is usually present, but the longer ones are often without it (Plate 39, figs. 34, 35, 37). When present the central tyle is, in var. gracilis, as much as 10 n, and, in var. robusta, as much as 20 n, thicker than the adjacent parts of the spicule; in transverse diameter they measure in the former 13-39 /x, and in the latter 25-70 fx. It either passes gradually into the body of the spicule (Plate 36, figs. 40, 44; Plate 39, figs. 36, 38) or it is set off from it more or less distinctly (Plate 36, figs. 31, 41-43). Most of these spicules are fairly isoactine, HYALONEMA (HYALONEMA) OBTUSUM. 163 some distinctly anisoactine (Plate 36, fig. 31; Plate 39, fig. 38). Their end-parts are thickened more or less to spherical tyles (Plate 36, figs. 31, the left one, 41, 44; Plate 39, figs. 34, 35, 36, the right one, 37) or spindle-shaped tyles (Plate 36, figs. 40, 42, 43). These distal thickenings are in var. gracilis usually smaller, rarely (Plate 36, fig. 44, the right one) stouter, than the central tyle. In var. robusta they attain much larger dimensions and have a maximum diameter of 90 /i. The middle-part of the spicule is smooth. The two ends are generally covered with spines, for a shorter or longer distance (Plate 39, fig. 38, the left one); they are rarely smooth (Plate 36, fig. 41; Plate 39, fig. 37). Although doubtless derived from the tetractines (triactines) among which they occur, these rhabds are hardly at all connected with them by transitional forms, and therefore readily distinguishable from them. The acanthophore rhabds, which are to be considered as derivates of the ordinary rhabds of the choanosome, are in var. gracilis (Plate 36, figs. 29, 30, 32- 39), where they appear to be more numerous than in the other variety, 0.6-2 mm. long and 10-18 ix thick in the middle. Most of them are rather uniformly curved throughout (Plate 36, figs. 29, 30, 32, 34-36), some are irregularly curved (Plate 36, fig. 33), and a few strongly angularly bent near the middle (Plate 36, fig. 39). Some of them are fairly isoact.ine (Plate 36, figs. 30, 37-39), others distinctly anisoactine (Plate 36, figs. 29, 32-36). All these spicules are more or less thick- ened at both ends. In the isoactine forms both terminal thickenings are slight, spindle-shaped, and situated a short distance below the end (Plate 36, figs. 30, 37, 38). In the anisoactine only one of the distal thickenings is of this nature, the other being stouter, 25-45 m in diameter, spherical or oval, and situated terminally (Plate 36, figs. 29, 32-36). The spindle-shaped thickening usually p asses gradually into the body of the spicule; sometimes it is distinctly set off from it (Plate 36, fig. 32). The shaft or body of the spicule is smooth. The ends are sometimes also smooth (Plate 36, fig. 33); usually, however, one (Plate 36, figs. 29, 36) or both (Plate 36, figs. 30, 32, 34, 35) of them bear spines. The axial thread is widened in the spindle-shaped distal thickenings (Plate 36, figs. 37, 38) and extends quite to their end. In the ray-ends thickened to a stouter, spherical or oval terminal tyle, the axial thread does not extend quite to the end. The silica-layers of the isoactine forms therefore appear as tubes open at both ends, those of the anisoactine forms as tubes open at one end only. An abnormal stout acanthophore 220 ^ in diameter was found in var. gracilis. Its rays are straight, cylindrical, terminally rounded, and very unequal in length, but all about 10 \x thick. The intermediate transitional acanthophores (Plate 39, figs. 1, 6, 11, 12) 164 IIYALONEMA (HYALONEMA) OBTUSUM. have rays which are in both varieties 4-6 n thick and covered with stout, blunt (Plate 39, fig. 1) or pointed (Plate 39, figs. 11, 12), usually curved, oblique spines 2-4 n long. The slender acanthophores (Plate 39, figs. 2-4, 13-16, 22-24) are mostly tetractine, triactine or diactine tetractine-derivates ; a few hexactine and pentac- tine forms appear to be pinule-derivates. In both varieties the rays of these spicules are sometimes 200 n long and, at the base, in var. gracilis 1.3-1. 5 m, in var. robusta 1.5-3. 5 n thick. They are usually curved more or less in an irregular manner and bear sparse, irregularly distributed spines. In both varieties these spines reach 6 m in length and are usually more or less curved. The spines arising from the end-parts of the rays are usually directed backwards and re- curved; the others are either also recurved, or vertical, or directed outwards. The basal parts of the rays appear always to retain their original, regular, relative position. In the tetractines these parts of the rays form regular rectangular crosses, in the triactines a T, and in the diactines usually a right angle. When a ray entirely disappears, a large spine usually takes its place (Plate 39, fig. 16). The rhabds of the choanosome and gastral cone are for the most part blunt amphioxes or amphistrongyles, but a few styles and tylostyles are also found among them. The blunt amphioxes and amphistrongyles of the choanosome and cone (Plate 33, figs. 1, 2, 18, 19, 21-23; Plate 39, fig. 39) are in both varieties nearly straight, slightly curved, or angularly bent, and usually provided with a more or less prominent central tyle. They are perfectly smooth. Their end-parts are generally somewhat wavy in outline. The amphioxes (amphistrongyles) of the upper part of the choanosome and the wall of the gastral cavity are 0.5-1.55 mm. long and 4-20 m thick near the central tyle. The tyle is 2-8 n thicker than the adjacent parts of the spicule, and measures 11-28 ^ in transverse diameter. When there is an angular bend the apex of the angle invariably lies in the central tyle (Plate 33, fig. 2). In the basal and the axial parts of the sponge these amphioxes (amphistrongyles) attain a larger size. They are here 1-3.5 mm. and more long and 8-50 ^ thick. The styles and tylostyles of the choanosome and gastral cone (Plate 33, fig. 20) are in both varieties shorter than the isoactine rhabds above described, usually only 0.9-1. 6 mm. long. The largest terminal tyles of the tylostyles observed were 30 n in diameter. The uncinate amphioxes of the superficial parts of the sponge (Plate 33, figs. 3, 4; Plate 39, figs. 25-30) are straight, or slightly curved, and sharp-pointed at both ends. They are in var. gracilis 580 u long, and 4.5-9 n thick in the middle. HYALONEMA (HYALONEMA) OBTUSUM. 165 In var. robusta they are larger, sometimes 1.1 mm. long and 20 n thick. A slight central thickening (tyle) with an axial cross in the interior can usually be made out, particularly in the smaller uncinates. This is generally about 0.5, rarely as much as 1 m thicker than the adjacent parts of the spicule. The spicule is covered with slender spines, all strongly inclined in the same direction. Near the end from which these spines diverge, they are rather numerous, towards the other end they become very scarce. So far as I could make out these spines consist of a rather broad conic basal part and a fine, exceedingly slender, neeclle- like end-part. The basal conic part arises steeply from the shaft and bends round above, where it passes into the fine end-part, so that the latter comes to lie nearly parallel to the shaft. The large stalk-spicules (Plate 40, figs. 21, 22), in var. robusta 8 mm. below their upper ends, where they are all broken off, are 40-720 /i thick. The empty spaces previously occupied by them in var. gracilis have a maximum width of 900 /d. The upper ends of these spicules of var. robusta are curved, the curvature increasing towards the (upper) end. The axial thread is for the most part 3-4 m thick. It does not lie centrally, but describes a spiral line around the mathe- matical axis of the nearly cylindrical spicule. It is by no means a simple cylindri- cal thread. Some parts of it (Plate 40, fig. 21) are uncinate-like, covered with strongly inclined spine-like processes directed upwards, others (Plate 40, fig. 22) are thickened, quite irregular, and attain 20 n in transverse diameter. In both varieties the regular microhexactines (Plate 35, figs. 14, 15, 17a, 18, 19; Plate 40, figs. 6, 7, 20b) measure 42-80 m in diameter. The six rays of the same spicule are fairly equal, and regularly arranged. The chords of the rays are 20-43 /j. long. The rays themselves are 1.5-2. 2 m thick at the base, gradually and uniformly attenuated distally to a fine point, and covered with very minute, vertically arising spines. The basal parts of the rays are nearly straight, the distal parts strongly curved through an angle usually a little over 90°. The direction of curvature of the end-part of each individual ray is generally opposite to that of the end-part of the ray opposite it in the same axis. The microhexactine-derivates (Plate 35, figs. 20-22; Plate 40, figs. 8-15, 20c) represent two series of forms. One begins with microhexactines in which the two rays lying opposite in the same axis are longer than the other four, and ends with centrotyle diactines. The other begins with micropentactines with equal rays, and ends with style monactines. In var. robusta forms of both series are rather frequent; in var. gracilis hardly any but diactine forms, with the two fully developed rays opposite in the same axis, have been observed. First series of microhexactine-derivates. One of the microhexactines, with 166 HYALONEMA (HYALONEMA) OBTUSUM. two opposite longer, and four shorter rays, with which the first series commences, is represented in Plate 40, fig. 9. This spicule is 117 n in length. Forms still farther removed from the regular microhexactine are produced by a further reduction of the four shorter rays of such a spicule. The reduction of the four shorter rays is either unequal or more or less equal. In the first case pentactines, tetractines, and triactines (Plate 40, fig. 11) with two opposite longer rays, and three, two or only one shorter, are produced ; in the second case forms like those represented on Plate 35, figs. 20-22, and Plate 40, figs. 12, 13, and 20c. In the extreme forms of this series all that remains of the shorter rays is a slight tyle (Plate 35, fig. 22; Plate 40, fig. 12). It is to be noted that a distinct increase in size of the two opposite, developed rays is, in these spicules, associated with the reduction of the four other rays. Such diactine microhexactine-derivates are, particularly in var. gracilis, more numerous than any of the others. They are in both varieties 1 56-204 n long, but in var. robusta considerably stouter than in var. gracilis, the basal parts of their properly developed rays being in the former 1.5-4 tx, while in the latter only 1.5-2. 5 m thick. The fully developed rays of these spicules are gradually attenuated to fine points, straight in their basal part and curved at the end. The reduced ones are straight throughout, cylindrical or cylindroconic, terminally rounded, and reach 6 n in length. The terminal curvature of the fully developed rays is not so great as in the rays of the regular microhexactines, nor is its direction generally opposite. To the second series of microhexactine-derivates belong the spicules repre- sented on Plate 40, figs. 8, 10, 14, and 15. The first (fig. 8) of these is a pentactine with equal rays, 100 ^ in diameter. The second (fig. 10) is a compass-shaped diactine. It consists of two fully developed rays, 47 n long, the basal parts of which enclose a right angle; and the insignificant rudiments of two other rays opposite to the two fully developed ones. The third and fourth (figs. 14, 15) are monactines. Such monactines are more frequent than the other forms of this series. They are 73-86 n long. Their single fully developed ray is 2.5-4 n thick at the base and tapers gradually to a fine point. It is straight in its basal part but strongly curved, through an angle of about 120°, in its distal part. These spicules are, like the regular microhexactines, covered with minute spines. In the larger ones the spines are more conspicuous than in the smaller ones, the size of the spines being, generally speaking, proportional to the thick- ness of the ray from which they arise. The pachymicrohexactines (Plate 39, figs. 7-10) are rather rare, and have only been found in the basal part of var. gracilis. I consider them as hypertrophic HYALONEMA (HYALONEMA) OBTUSUM. 167 microhexac tines. They consist of six fairly equal rays joined at right angles, and measure 52-80 n in total diameter. Their rays are cylindrical, of nearly uniform stoutness throughout, and rounded at the end. They are 26-42 p long, 5-15 m thick, and generally quite smooth. Their basal part is straight, their end-part either straight (Plate 39, fig. 7) or more or less curved (Plate 39, figs. 8-10). Axial threads, terminating however a considerable distance below their ends, can be easily made out in the rays of these spicules. Among the amphidiscs of var. gracilis two main groups can be distinguished morphologically: — large forms, the largest of which have broad and rather short terminal anchors and a stout, spiny shaft; and small forms the largest of which have long and very slender terminal anchors and a slender shaft with very small spines. In each of these main groups, which I name macramphidiscs and micr- amphidiscs respectively, two subgroups can be distinguished: — in the macram- phidiscs larger forms with relatively shorter, and smaller forms with relatively longer, terminal anchors; in the micramphidiscs larger forms with long and slender anchors, and smaller forms with shorter and broader anchors. The biological length frequency-curve of these amphidiscs exhibits (Fig. 4) a gap between the lengths 54.76 p and 66.26 n. The amphidiscs, to which the part of the curve to the right of the gap pertains, are the amphidiscs referred to above as macramphidiscs; those to the left of the gap as micramphidiscs. Each of these two parts of the curve exhibits a conspicuous depression dividing it into two distinct elevations. These elevations correspond to the smaller and larger kinds of the macramphidiscs and the micramphidiscs, which are, as above stated, also distinguished from each other morphologically by the shape of their terminal anchors. Thus both the morphological and the biometrical qualities of these amphi- discs show that four kinds of these spicules are to be distinguished in var. gracilis: — large macramphidiscs, small macramphidiscs, large micramphidiscs, and small micramphidiscs. The amphidiscs of var. rohusta also fall into these four groups. The large macramphidiscs of var. gracilis (Plate 37, figs. 20-22) are some- what infrequent. They are 250-356 n long, most frequently about 1 264 /x, and have a straight shaft 8-14 n thick. This is thickened slightly and gradually to 14-22 /x at the ends, and abruptly in its middle-part to a central tyle 15-18 n in diameter. The tyle never appears to lie quite in the middle ; the difference 1 This phrase “ most frequently about ” refers, throughout the descriptions, to the summit of that part of the length frequency-curve of the graph which pertains to the amphidiscs in question. 168 HYALONEMA (HYALONEMA) OBTUSUM. Length of Amphidiscs (/A Fig. 4.- — ■ Length frequency-curve. between its distances from the two ends is 7-37 n, 3%-15% of the length of the whole spicule. In the shaft an axial thread is distinctly visible (Plate 37, fig. 21). This thread appears to be quite simple and it certainly does not give off branches in the central tyle. From the central tyle, and also from other parts of the shaft, spines arise. The spines of the central tyle are generally five to eight in number and arranged in a more or less regular verticil. They are conical, blunt-pointed, or truncate, 9-14 n long, exceptionally 18 n, and 5-7 n thick at the base; the truncate ones bear minute secondary spinelets on their ends. The other spines are irregularly scattered over the middle-part of the shaft. The thickened conical end-parts of the shaft are free from spines. These spines are not very numerous; often there are a good many more spines on one side of the central tyle than on the other. Most of these spines are vertical to the axis of the shaft; a few of them are, however, oblique, inclined toward the centre of the spicule. These scattered spines are similar in shape and about as stout, but, as a rule, are shorter than the spines of the central tyle. The spines are destitute of axial threads. HYALONEMA (HYALONEMA) OBTUSUM. 169 The two anchors of the same spicule are equal or slightly unequal in size. The greatest differences between them in length and breadth observed were 12 and 8 p respectively. The anchors are 70-100 p, that is generally a little less than a third of the whole spicule in length, and 70-95 p broad. The proportion of length to breadth in these anchors is 100 to 60-108, on an average 100 : 93.2. Each anchor consists of eight recurved teeth. The teeth of the same anchor are fairly equal and regularly arranged. Their axes extend in planes passing through the axis of the shaft and enclosing angles of 45° with their neighbours. The individual teeth arise nearly vertically from the shaft, and then curve con- cave towards it. This curvature in the basal part of the tooth is for some distance fairly uniform, but it decreases distally. Towards its end the tooth is hardly at all concave to the shaft, or straight, or even slightly convex to the shaft. The whole curvature amounts to about 90°, the end-parts of the teeth being nearly parallel. Seen en face (from above) the individual teeth are elon- gate oval in appearance, 10-16 p broad in the middle, and rounded or pointed at the end. Seen in profile they appear stoutest at the base and are at first gradu- ally, and near the end abruptly, attenuated to a sharp point. Each anchor- tooth somewhat resembles a T-iron. It consists of an outer band-shaped part, and an inner keel. The outer band-shaped part is broadest in the middle, at- tenuated towards both ends, and bent, concave to the shaft, both transversely and longitudinally. Its transverse convexity increases, and its longitudinal convexity decreases, towards the distal end. The inner keel is highest at the base of the tooth; towards its distal end it becomes lower, at first gradually, then more abruptly. The large macramphidiscs of var. robusta (Plate 40, figs. 1, 2, 19) are similar to those of var. gracilis, but larger and provided with somewhat thicker shafts and broader anchors. They are 235-335 p long, most frequently about 297 p. The shaft is 10-17 p thick. Its central tyle measures 15-18 p in diameter. The anchors are 70-100 p in length, that is about a third of the whole spicule, and 90-110 /j. broad. The proportion of the length to the breadth of these anchors is 100 to 95-150, on an average 100 : 117.6. The small macramphidiscs of var. gracilis (Plate 34, fig. 19b; Plate 35, fig. 24b; Plate 37, figs. 12-19; Plate 38, figs. 4-8) are 86-212 p long, most fre- quently about 164 fx. The shaft is 2.5-9 p thick, and thickened in or near the middle to a central tyle 4-12 p in diameter. The shaft bears spines similar to those on the shafts of the large macramphidiscs. These spines are 5-12 p long and 2-3.5 p thick. The terminal anchors are 32-72 p in length, usually a little 170 HYALQNEMA (HYALONEMA) OBTUSUM. more than a third of the whole spicule, and 16-69 m broad. The proportion of the length to the breadth of the anchors is 100 to 56-96, on an average 100 : 81.2. The individual anchor-teeth are strongly curved in their basal part. Distally their curvature decreases and their end-parts, a third to a half of their total length, are nearly straight and parallel. The small macramphidiscs of var. robusta are similar but stouter and pro- vided with broader terminal anchors. Their measurements are: — length, 146- 205 /d, most frequently about 176 m! thickness of shaft 4-11 n; anchor-length 45-80 /d, usually a little over a third of the length of the whole spicule; proportion of anchor-length to anchor-breadth, 100 to 72-112, on an average 100 : 81.2. The large micramphidiscs of var. gracilis (Plate 37, figs. 6-11) are 28.5-68 m long, most frequently about 32.4 The shaft is 0.8-1. 5 m thick. It always bears a few spines in or near the middle, and usually some also elsewhere. The central spines do not form verticils. The spines are 0.4-1 /x long, about as thick, and usually cylindrical and terminally rounded, or truncate. The two anchors of the same spicule are very similar, the greatest difference observed in their lengths and breadths being 2 n and 1 ^ respectively. The anchors are 11-24 ^ in length, that is a little over a third of the whole spicule, and 6-10 ,u broad. The proportion of the length to the breadth of the anchors is 100 to 44-64, on an average 100 : 52.6. The individual anchor-teeth of the smaller forms of these spicules are strongly curved in their basal parts and fairly straight in their distal parts, their total curvature being such that their tips are nearly parallel (Plate 37, figs. 6, 7). In the larger forms the teeth are relatively longer, and the curvature of their basal part stronger, whilst their end-parts are slightly curved in the opposite direction, convex to the shaft. The tips of the teeth of these amphidiscs are parallel or convergent, and the anchors themselves at the end sometimes as much as 3 m narrower than in their broadest, more proximal part. This gives to these spicules quite a peculiar appearance (Plate 37, figs. 8-11). In var. robusta no amphidiscs have been observed similar to the larger forms of the large micramphidiscs with distally attenuated anchors; all the large micramphidiscs of var. robusta are similar in shape to the smaller forms of the large micramphidiscs of var. gracilis. The dimensions of the large micramphi- discs of var. robusta are: — length 27-64 /d, most frequently about 45.5 /x; anchor-length 11-25 m, about two fifths of the length of the whole spicule; anchor-breadth 7-26 /x; proportion of anchor-length to anchor-breadth 100 to 64-104, on an average 100:84. HYALONEMA (HYALONEMA) OBTUSUM. 171 The small micramphidiscs of var. gracilis (Plate 35, fig. 17b; Plate 37, figs. 1-5; Plate 38, figs. 1-3) are 13-26 /i long, most frequently about 16.7 n- The shaft is straight and 0.5-1. 2 n thick. It bears in its central part a few short and broad, terminally rounded protuberances. The terminal anchors are 5-9 fx in length, that is a third to two fifths of the whole spicule, and 4.2-8 n broad. The proportion of the length to the breadth of the anchors is 100 to 55-120, on an average 100 : 90. The small mi cramphi discs of var. robusta (Plate 40, figs. 16-18, 20a) are similar but somewhat smaller. Their measurements are: — length 12-23 n, most frequently about 16.2 n; anchor-length 3.8-7 n, that is about a third of the length of the whole spicule; anchor-breadth 4-5 n; proportion of anchor-length to anchor-breadth 100 to 72-125, on an average 100 : 90. A few young forms of micramphidiscs were observed in var. robusta. These spicules (Plate 40, fig. 18) have a centrotyle and spiny shaft thickened at both ends. Their anchors appear as terminal verticils of small vertically arising and slightly recurved teeth. The two specimens described are in respect to their spiculation similar enough to be considered the same species. Their skeletal elements, however, differ in detail, the spicules generally, and particularly both the stout and the slender tetractine and tetractine-derivate acanthophores, having much stouter rays. The uncinates are larger and the anchors of both kinds of macramphi- discs and of the large micramphidiscs are relatively considerably broader in the specimen from Station 3681 (A. A. 2) than in the specimen from Station 3684 (A. A. 17). For this reason and because the two specimens differ con- siderably in outer appearance and come from localities a good distance (over 3000 km.) apart, I think it advisable to consider them as two distinct varieties. The only species of Hyalonema which appears to be at all closely allied to these sponges is the one described in this report as Hyalonema ( H .) agassizi. From this they differ chiefly by their macramphidiscs and large micramphidiscs having more strongly curved and less divergent teeth, by their microhexactines being smaller and having more strongly curved rays, by the spicules of their acantho- phores being larger, and by the rays of the slender acanthophores having longer spines. 172 HYALONEMA (HYALONEMA) AGASSIZI. Hyalonema (Hyalonema) agassizi, sp. nov. Plate 41, figs. 1-14; Plate 42, figs. 1-59; Plate 43, figs. 1-7; Plate 44, figs. 1-30; Plate 45, figs. 1-64; Plate 46, figs. 1-16; Plate 47, figs. 1-13. Eleven more or less complete specimens and three fragments of this species were trawled in the Tropical Pacific at five stations. One of these sponges is a very fine specimen, the best in the collection. It is therefore appropriate to name this new species after the leader of the several Albatross expeditions which brought home the material here reported on. Two of the five specimens from Station 4742 are cake-shaped, the three others more elongate, pear- or top-shaped. The general appearance and the spiculation of the fragments indicate that they are parts of similar pear- or top- shaped sponges. The two cake-shaped specimens from Station 4742 appear to be identical in structure among themselves, but to differ from all the rest. The same is to be said of the three pear- or top-shaped specimens and the fragments from the same station, and of the three specimens from Station 4740. The speci- mens from the three other stations all differ from each other and from the rest. I shall, for the reasons given below, describe these six different kinds as distinct “forms”:— A, the one taken at Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.); bottom composed of fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. B, the one taken at Station 4651 on 11 November, 1904; 5° 41.7' S., 82° 59.7' W. ; depth 4063 m. (2222 f.) ; bottom a sticky, fine gray sand; bottom-tempera- ture 35.4°. C, the three from Station 4740 taken on 11 February, 1905; 9° 2.1' S., 123° 20.1' W. ; depth 4429 m. (2422 f.); bottom composed of dark gray Globigerina ooze; bottom-temperature 34.2°. D, the one taken at Station 3684 (A. A. 17) on 10 September, 1899; 0° 50' N., 137° 54' W.; depth 4504 m. (2463 f.); bottom light yellow-gray Globi- gerina ooze. E, the two caked-shaped specimens, and F, the three pear- or top-shaped specimens and the fragments, all from Station 4742, on 15 February, 1905 ; 0° 3.4' N., 117° 15.8' W.; depth 4243 m. (2320 f.); bottom composed of very light, fine Globigerina ooze; bottom- temperature 34.3°. Shape and size. The single specimen of form A (Plate 41, fig. 2) is well- HYALONEMA (HYALONEMA) AGASSIZI. 173 preserved. Its body is broad top- or spindle-shaped, has at every level a nearly circular transverse section, and measures 66 mm. in length and 48 mm. in maxi- mum transverse diameter. At its apex the rounded summit of the nearly cylin- drical gastral cone is visible. The cone is surrounded by a circular wall which terminates in a narrow frill, the margin of which appears as a circle 8 mm. in diameter. The circular wall is separated from the cone by a circular fissure about 1 mm. wide. This fissure is the gastral cavity. The outer surface of the sponge-body is quite smooth and continuous; apertures, visible to the naked eye, do not occur in it. From the lower, rounded end of the body the stalk arises. At its origin this is about 5 mm. thick, thickens slightly below, and measures a little over 40 cm. in length. The spicules composing it are all broken off at the lower end; in life the stalk was probably considerably longer. Its lower and central parts are quite straight. Its upper part is strongly and uniformly bent- through an angle of about 60°. The single specimen of form B (Plate 41, fig. 1) is not so well-preserved. Of its dermal membrane only a few patches are left and the upper part is much torn. It is massive, pear- or club-shaped, 81 mm. long and 61 mm. broad. The stalk is straight, 7 mm. thick at the point of origin and broken off at a distance of 9 cm. from the sponge-body. Although, as above stated, the upper part of the sponge is much torn, one can make out in the middle of it a nearly cylindrical, terminally rounded gastral cone about 10 mm. thick, connected by four radial, vertical, membraneous plates joining it with the gastral wall. The surface appears very rough and uneven. This is doubtlessly due to the loss of the dermal membrane. The three specimens of form C are cake-shaped. Of their dermal mem- branes and the stalks only slight remnants remain. The best preserved one (Plate 41, figs. 13, 14) is a stout, marginally rounded disc, broad-oval, nearly ■circular in outline. It measures 66 mm. in length, 60 mm. in breadth, and 27 mm. in thickness (height). The lower face is nearly flat, the upper convex. The centre of the latter is occupied by a gastral depression 20 mm. in diameter, nearly circular in outline, and surrounded by a circular wall on the margin of which remnants of a thin frill can be made out. Where this frill is best preserved it appears to be turned outward. A low, dome-shaped, gastral cone about 6 mm. thick arises from the centre of the depression. This cone is connected with the gastral wall by four vertical,' radial membraneous plates. The wide spaces between these radial plates appear as diverticular parts of the gastral cavity, which are continued down into the interior of the sponge. A few stalk-spicules, 174 HYALONEMA (HYALONEMA) AGASSIZI. broken off 1-3 cm. from the sponge, arise from the centre of the flat lower face. Many parts of the surface, particularly of the upper side, exhibit a reticulate appearance, caused by the presence of a superficial network with irregularly square meshes, the centres of which are about 1 mm. apart (Plate 41, fig. 14). The centre of each mesh is occupied by the circular entrance to an afferent canal. The other two specimens of this form are similar. One of them is about as long and broad as the one above described, but thicker (higher) ; the distance between the summit of its gastral cone and the slight protuberance on its lower face, from which the (absent) stalk arose, being 40 mm. The other is smaller, has no trace of a stalk, and measures 45 by 37 by 12 mm. The single specimen of form D is also indifferently preserved. A few small remnants of the dermal membrane and some stalk-spicules, broken off short, are, however, still present. This sponge (Plate 41, fig. 12) is also cake-shaped. It measures 51 mm. in length, 46 mm. in breadth, and 17 mm. in thickness (height) . The larger and more complete of the two specimens of form E is cake- shaped, 36 mm. long, 28 mm. broad, and 25 mm. thick (high). In the middle of its flattened upper face there is a gastral depression, surrounded by a thin circu- lar wall with sharp margin. This margin is nearly circular and measures 13 mm. in diameter. In the centre of the depression a low gastral cone is situated, from which radiate several somewhat irregularly disposed vertical plates. Between these plates wide diverticula of the gastral cavity extend downwards to a dis- tance of about 14 mm. A protuberance 5 mm. high is observed in the middle of the lower, more convex face of the sponge. The holes in it indicate that, in life, the spicules forming the stalk arose from this protuberance. The other specimen of this form is very similar. It measures 34 by 28 by 21 mm. The most complete specimen of form F is laterally compressed and appears as an irregularly triangular plate about 5 mm. thick. The plate is 30 mm. broad above and narrows below to 5 mm. A bundle of stalk-spicules arises from the lower end. The other two specimens of this form are more fragmentary and consist only of the central and the attenuated basal part of the sponge-body, and the upper part of the stalk. One is (without the stalk) 37 mm. long, the other 35 mm. The largest of the fragments of this form is 28 mm. long. The colour of the specimen of form A in spirit is a rather rich coffee-brown, of form B a dirty light greenish gray, of form C a light reddish brown, of form D a light dirty brown, and forms E and F are whitish. Canal-system. The canal-system of form A (Plate 45, figs. 18, 23) seems to HYALONEMA (HYALONEMA) AGASSIZI. 175 be similar to that of Hyalonema ( Hyalonema ) obtusum var. gracilis; the chief difference apparently being that the former is more dense and has narrower subdermal cavities and canals. The flagellate chambers are elongate and 50-80 m broad. In one of the specimens of form C the afferent canals are very clearly visible. They here appear as tubes, about 0.5 mm. wide, which lie parallel side by side and extend vertically down into the interior of the choanosome. In this form, and in the forms B, D, and E, the gastral cavity is divided by radial vertical plates into diverticula. The plates are, in several of these specimens, four in number and regularly arranged in a cruciate manner. The diverticula extend downward, are tubular, very wide above, attenuated below, and nearly circular in transverse section. Their walls are perforated by numerous efferent apertures, many of which attain considerable dimensions. Skeleton. The whole of the outer surface of form A, and the (small) parts of it, in the other forms where the dermal membrane is still present, are covered by a dense pinule-fur (Plate 42, fig. 36; Plate 45, fig. 23a). Certainly in form A and probably also in the other forms, the pinnies of all parts of the outer surface are similar, with the exception of the part close to the origin of the stalk. They are in all forms for the most part pentactines; a few, however, possess a more or less developed sixth, proximal ray, and appear as hexactines. Between the lateral rays of these dermal pinules a few micramphi discs lie scattered on the outer surface. From the thin, upper, free margin of the wall surrounding the gastral cavity (fissure or depression) the distal rays of cliactine pinules protrude. The gastral surface, that is the inner surface of the wall surrounding the gastral cavity, and the surface of the gastral cone are likewise covered by a pinule-fur. The pinules composing it are chiefly pentactines, more rarely hexactines, excep- tionally diactines. A few minute spiny pentactines have also been observed here. On these gastral surfaces also micramphidiscs occur. These spicules are here, however, much more abundant than on the outer surface, and in places form dense masses. Below, where the gastral cavity passes into the large effer- ent canal-stems, the pinule-fur ends; the coating of micramphidiscs, however, is continued along the walls of these canals quite down to the innermost parts of the choanosome. The micramphidiscs of the outer, dermal surface and of the surfaces bordering on the upper part of the gastral cavity and enclosing the inner, proximal parts of the efferent canals, are all or nearly all small ones. Those on the surfaces surrounding the lower proximal part of the gastral cavity and the mouths of the large efferent canals on the other hand are, certainly in form A, and probably also in the other forms, in great part large macramphidiscs. 176 HYALONEMA (HYALONEMA) AGASSIZI. Just below the level in which the lateral rays of the dermal pinules of the outer surface extend, the paratangentially situated lateral rays of hypodermal pentactines are met (Plate 42, fig. 37a; Plate 45, fig. 23). In form C these lateral pentactine rays extend in the beams of the superficial network above described. The apical rays of the hypodermal pentactines extend radially in- ward. In form A a superficial zone about 0.6 mm. thick, underlying the dermal membrane, is occupied by dense masses of more or less radially arranged unci- nates and irregularly scattered microhexactines and microhexactine-derivates (Plate 45, fig. 23). This zone contains no spicules besides these and the proxi- mal rays of the hypodermal pentactines, which traverse it. Below this zone hexactine megascleres begin to make their appearance. Those lying nearest the surface are quite small, towards the interior they increase in size. Though often irregularly disposed in the sections, these spicules are, in the living sponge, in all probability regularly arranged in such a manner that two opposite rays extend longitudinally upward and downward, two radially outward and inward, and two paratangentially and laterally to the right and left. In most of the large and in a good many of the smaller hexactines the two opposite longitudinally extending rays are longer than the other four. Masses of large macramphidiscs are met with a little below the level where the hexactines begin to make their appearance. In some places these form but a thin layer, in others they extend a considerable distance, 2 mm. or more, into the interior of the choanosome. The inner parts of the sponge are occupied by the large hexactine mega- scleres referred to above, and also by rhabd-megascleres, uncinates, microhexac- tines, microhexactine-derivates, amphidiscs, and spheres. The large inner hexactines usually have two opposite, longitudinally extend- ing, greatly elongated rays and four shorter transverse rays. The rhabds of the axial part of the sponge are situated longitudinally and form a kind of axial column, which extends upwards to the summit of the gastral cone. Loose strands of rhabds diverge from this axial column and extend upwards and out- ward. Below, in the interior of the choanosome, these diverging rhabd-strands dissolve into scattered, obliquely situated, isolated rhabds; above they join to form distinct layers lying below the dermal and the gastral surfaces of the thin frill-like marginal part of the gastral wall. In the forms B, C, and D masses of longitudinal rhabds also occupy the vertical radial plates connecting the gastral cone with the gastral wall. Most of these rhabds are very blunt amphioxes or amphistrongyles ; but sharp-pointed amphioxes, amphityles, styles, and tylo- styles also occur among them. In the axial column of form A both large and HYALONEMA (HYALONEMA) AGASSIZI. 177 small rliabds are met. Outside the axial column, however, only the smaller ones have been observed. In the interior the uncinates are not very numerous and are irregularly scattered. Of amphidiscs both macramphidiscs and micramphidiscs occur in the interior. The former are very scarce, the latter, which appear chiefly to occupy the walls of the efferent canals, exceedingly numerous. The micro- hexactines and their derivates are, in the interior, rather frequent, but not nearly so abundant as in the superficial region. The spheres appear to be restricted to the axial column, where they occur singly or, more rarely, in clusters. They are rather numerous in form A and have also been found in form D. In the specimens of form A, B, and in two of the specimens of form F the stalk is more or less intact. It is in these forms composed of stouter and more slender rods, broken off at the lower, distal end. In the specimen of form A the stalk is over 40 cm. long and now consists of twenty spicules; in life there may have been more. The spicules composing it are very distinctly spirally twisted, like the strands of a rope and also similarly entwined. The twist has the same direction in all. Progressing from the proximal to the distal end the spiral curvature is in the direction of the movement of the hands of a watch. The stalk-spicules extend for some distance upwards into the sponge-body, and they are, in the basal part of the latter, surrounded by masses of acantho- phores. These are stout-rayed, usually terminally spined tetractines (staurac- t.ines), derivates of these spicules, more or less spiny pentactines, modified pinules, and modified rhabds with spiny ends. In the basal part of some of the specimens spheres also occur. In the specimens of all the forms with the excep- tion of those of forms E and F, slender-rayed, long-spined spicules with four to six rays also occur just below the surface of that part of the body from which the stalk arises. Their absence in forms E and F is probably due to the frag- mentary nature of the specimens of these forms. The dermal pinules (Plate 42, figs. 20-23, 25-36, 37b, 42b) are nearly all pentactine; only a few are hexactine. Their distal ray, in form A (Plate 42, figs. 25-28, 35, 36), is straight, 93-110 m long, usually 94-107 /i, on an average 100.4 /x; and, at the base, 4.4-7 ^ thick, usually 4. 5-6. 7 /x. Above it thickens, and it ends with a well-developed, smooth, terminal cone 6.5-1 1 n thick, usually 8.5-9 t±. The proximal, basal part of the ray and its terminal cone are free from spines; the rest of it, usually about 60% of its length, is covered with spines. The most proximal spines diverge strongly, and are often nearly vertical to the ray. Distally they become more inclined towards the tip, and the uppermost 178 HYALONEMA (HYALONEMA) AGASSIZI. spines, which surround the terminal cone, are nearly parallel to the ray-axis. The lowest spines are straight and quite short. Distally they become slightly curved, concave towards the tip of the ray. Up to the middle of the length of the ray they increase in size; beyond they again become smaller. The largest spines on the middle-part of the ray are 10-20 n long and 2-4 /x thick at the base. The maximum transverse diameter of the distal ray, together with its spines, is 18-32 n, usually 20-30 n, on an average 23.6 /x. The lateral rays of the same spicule are usually fairly equal (Plate 42, fig. 35), sometimes considerably unequal (Plate 42, fig. 36). They are 21-32 m long, straight, nearly cylindrical in their basal part, attenuated toward the end in their distal part, and blunt-pointed or terminally rounded. The proximal parts of the lateral rays are usually rather smooth; their distal parts bear sparse small spines. A sixth proximal ray is observed very rarely and, when present, is short and rudimentary. The dermal pinules of form B (Plate 42, fig. 29) are very similar but have a shorter and more bushy distal rays and longer lateral rays. The distal ray is 85-97 n long, on an average 93 n, and 3.5-6 n thick at the base. Its maximum transverse diameter, together with the spines, is 28-34 n, on an average 29.2 /x. The lateral rays are 25-30 ix long. The dermal pinules of form C (Plate 42, figs. 20-23) are even more similar to those of form A, but have a slightly more bushy distal ray and longer lateral rays. The distal ray is 95-1 14 n long, on an average 104.9 m, and 4-6 /x thick at the base. Its maximum transverse diameter, together with the spines, is 22-32 n, on an average 27 /x- The lateral rays are 25-35 m long. The dermal pinules of form D (Plate 42, figs. 30-34, 42) differ from those of the other forms by the distal ray being not so long, having a shorter and stouter terminal cone, and being covered with more numerous and crowded spines. The distal rays of the dermal pinules of this form therefore appear, when com- pared with those of the other forms, more stunted, stout, and dense. The distal ray is 82-101 n long, usually 87-95 ix, on an average 89.1 m, and at the base 4.5-8 /x thick, usually 4.5-6 ix. Its maximum transverse diameter, together with the spines, is 23-32 /x, on an average 26.2 /x. The terminal cone is 8-11 m thick. The lateral rays are 17-30 /x long, exceptionally up to 38 /x . The dermal pinules of form E have a distal ray 70-94 ix long, on an average 86.7 /x. Its maximum thickness, together with the spines, is 22-32 /x. The lateral rays are usually 18-23 m long. The dermal pinules of form F have a distal ray 85-97 /x long, on an average 90 ix. Its maximum thickness, together with the spines, is 23-25 ix. The lateral rays are usually 23-43 /x long. HYALONEMA (HYALONEMA) AGASSIZ I. 179 Peculiar, very variable, modified pinules (Plate 42, figs. 38-41, 43-45, 47, 48) occur in the basal region, where the large stalk-spicules enter the sponge- body. These spicules appear to be dermal pinules changed in shape and in part pushed into the interior by the stresses arising in this region from the resistance of the embedded upper ends of the stalk-spicules to the weight of the sponge-body, and to such passive movements of it as may be caused by the impact of moving deep-sea animals. Transitional forms appear to connect these modified pinules with the slender-rayed, long-spined basal tetractines and other spicules described below. The modified basal pinules of form A (Plate 42, figs. 38-41) are pentactine or hexactine. The distal ray is straight, 78-120 /x long, and 2.5-6 n thick at the base. It bears, in its middle- and end-parts, sparse, strongly divergent spines, which are sometimes irregularly distributed, and are more numerous on one side than on the other (Plate 42, fig. 40). These spines are slender, conic, pointed, straight or slightly curved, simply or in an S-shaped manner; they are 15-29 n long and 1.3-3 n thick at the base. The maximum transverse diameter of the distal ray, together with the spines, is 18-42 n. The lateral rays of the same spicule are equal or unequal. They are straight, 30-57 m long, conic, usually pointed, and covered with spines directed obliquely outward. The largest of these spines are 1.5-2 /x long. The proximal ray (of the hexactine forms) is 42-55 ix long; in shape and spinulation it resembles the lateral rays. The modified basal pinules of form B (Plate 42, figs. 47, 48) are similar but have shorter and stouter rays. The distal ray is 83-94 m long and 4-6 m thick at the base. Its maximum diameter, together with the spines, is 28-35 ix. The spines of the distal ray are 18-24 n long and 2. 5-2. 7 n thick at the base. The lateral rays are 25-32 /x long. Some of the modified basal pinules of form C (Plate 42, figs. 43, 44) are considerably larger than those of the other forms. The distal ray is 101-135 n long and 4.5-5 n thick at the base. Its maximum transverse diameter, together with the spines, is 13-33 n. Its spines are 14-15 /x long and about 2.3 ^ thick at the base. The lateral rays are 20-80 m long. In form D, E, and F, I found only few modified basal pinules (Plate 42, fig. 45). One of form D which I measured had a distal ray 82 /x in length and, together with the spines, 28 /x in maximum thickness. Its largest spines meas- ured 18 by 2.5 ix. The frill on the margin of the gastral wall, containing the diactine pinules , is preserved in a satisfactory manner only in the specimen of form A. The diactine marginal pinules of this form (Plate 44, figs. 1-5) have a total length 180 HYALONEMA (HYALONEMA) AGASSIZI. of 350-640 fj.. The distal ray is 148-245 m long, fairly straight, 6-9 m thick at the base, and thickened above. It ends with a smooth, rather slender, sharp- pointed terminal cone. All parts of it, with the exception of its basal portion and its terminal cone, are covered with spines strongly inclined towards the tip. The largest spines are situated about a third of the length of the distal ray from the tip. From here they decrease in size both distally and proximally. The largest spines are 6-7 m long and 2-3 m thick at the base. The maximum trans- verse diameter of the distal ray, together with the spines, is 15-26 m- The lateral rays are generally reduced to mere rounded protuberances, only exceptionally as much as 9 m high (Plate 44, fig. 2, the left one). Together they form a central tyle 11-21 /x in diameter. The proximal ray is straight or slightly curved, 175-400 n long, and, at the base, as thick as the distal ray. It usually bears a few spines and a number of very low and broad rounded protuberances which render the appearance of its outline somewhat wavy. I have observed a few transitional forms which appear to connect these diactine pinnies with ordinary, centrotyle, amphiox megascleres. The ray corre- sponding to the distal ray of the diactine pinnies of one of these spicules, which I measured, was perfectly smooth, 680 \x long, and 22 /x thick at the base, and thickened above the middle of its length to 26 /x. Its central tyle measured 30 ix in transverse diameter. The gastral pinules (Plate 42, figs. 1-8, 10-19, 24). In form A, where the gastral pinules both on the cone and on the inner face of the gastral wall could be conveniently measured, I found the distal rays of the former markedly longer than the distal rays of the latter, and also noticed that the distal rays of the pinules of the gastral wall decreased in length towards the upper, free margin. The gastral pinules of the cone of form A (Plate 42, figs. 1-8, 10-13) are for the most part pentactine; a few, however, are hexactine (Plate 42, figs. 1, 2) and one that I observed was diactine (Plate 42, fig. 13). The distal ray in these pinules, when normally developed, is 97-135 /x long, usually 100-134 /x , on an average 118.2 n, and 3. 5-9. 5 m thick at the base. One (Plate 42, fig. 8) that had apparently been broken off during growth and then partly regenerated was only 65 /x long. The distal ray-ends with a smooth, blunt, terminal cone 4.5-9 m thick. This and the basal part of the ray are destitute of spines. The remaining parts of it bear somewhat sparse spines. The proximal spines are strongly divergent, only slightly inclined, and curved towards the tip of the ray. Distally they become more inclined in this direction, but are, on the whole, much more divergent than those of the dermal pinules. The spines attain their great- HYALONEMA (HYALONEMA) AGASSIZI. 181 est length near the middle of the ray and from here decrease in size both proxi- mally and distally. The largest spines are 10-21 /x long and 2.5 n thick at the base. The maximum transverse diameter of the distal ray, together with the spines, is 21-41 /x, usually 30-40 /i, on an average 34.1 /x. The lateral rays of the pentactine and hexactine gastral cone-pinules are, in the same spicule, fairly equal (Plate 42, figs. 1, 10, 11) or more or less unequal (Plate 42, figs. 3, 5, 12), some of the lateral rays of the same spicule often being short, cylindrical, and terminally rounded, the others long, conic, and pointed. The individual lateral rays are 20-S5 m long, straight, cylindrical, and terminally rounded, or conic and pointed at the end. Their basal part is usually quite smooth, their distal part for two thirds or more of their length is covered with more or less conspicuous spines. The proximal ray in the hexactine forms is 17-76 /x long, gradually attenuated towards the end, or abruptly pointed. It is smooth throughout, or covered with spines in its distal part. The proximal ray of the diactine cone-pinule (Plate 42, fig. 13) is 95 n long. The gastral pinules of the inner surface of the gastral wall of form A are similar to those of the cone, but have distal rays only 91-112 n long. The gastral cone-pinules of form B (Plate 42, figs. 14, 15) are pentactine or, more rarely, hexactine and similar to those of form A. They have, however, shorter distal rays with more divergent and longer spines. The distal ray is in these spicules 83-109 n long, on an average 98.2 n, and 5-7 n thick at the base. Its maximum transverse diameter, together with the spines, is 27-45 /x, on an average 34.4 /x. Its largest spines attain a length of 25 n. The lateral rays are 30-48 /x long, the proximal ray (of the hexactine forms) is 12-27 /x long. The gastral cone-pinules of form C (Plate 42, figs. 16, 17) have a longer distal ray than those of form B and resemble those of form A very closely. The distal ray in these spicules is 110-127 /x long, on an average 118.5 n, and 4. 5-5. 5 m thick at the base. Its maximum transverse diameter, together with the spines, is 24-29 The lateral rays are 35-50 n long. The distal rays of the gastral pinules of the inner surface of the gastral wall of form C (Plate 42, figs. 18, 19) are similar in size but have more divergent spines and consequently, together with the spines, a greater maximum trans- verse diameter. The divergence of the proximal spines from the tip of the ray is so great that some of them stand vertical, and some even point the opposite way. The distal ray is 103-126 /x long, on an average 115 /x, and 5-6 /x thick at the base. Its maximum transverse diameter, together with the spines, is 28-35 n. The lateral rays are 36-50 n long. 182 HYALONEMA (HYALONEMA) AGASSIZI. The gastral pinnies of the cone of form D (Plate 42, fig. 24) resemble those of form A rather closely. They have a distal ray 98-113 /x long, on an average 106.7 yu, and 6. 5-8. 5 n thick at the base. Its maximum transverse diameter, together with the spines, is 25-38 /z. The lateral rays are 26-64 /x; the proximal ray (of the hexactine forms) is 38-50 m long. The gastral pinnies of form E have a distal ray 69-103 /x long, usually 83- 99 /x, on an average 90.5 and 4.5-7 /x thick at the base. Its maximum thickness, together with the spines, is 21-37 m- The lateral rays are 21-57 m long. In two hexactine gastral pinules of this form measured, the proximal ray was 42 and 44 /x long respectively. The gastral pinules of form F have a distal ray 100-153 /x long, on an average 129 fji, and 5-6 m thick at the base. Its maximum thickness, together with the spines, is 25-40 n. The lateral rays are 50-62 /x long. Minute pentactines with spiny rays (Plate 42, figs. 9, 50) were found in small numbers in the spicule-preparation of the gastral cone of form A, and the basal part of forms A and B. These pentactines have straight, conic, blunt-pointed rays, smooth at the base, but covered with conspicuous spines in their distal part. Their apical ray in form A is 36-80 m long, in form B 43-65 n, and is in both 3-6 m thick at the base. The lateral rays of the same spicule are equal. In form A they are 40-50 /x long, in form B 25-42 yu, and about as thick as the apical ray. The hypodermal pentactines of form A (Plate 41, figs. 3-11; Plate 45, fig. 23) have a fairly straight, conic, and blunt apical (proximal) ray, which measures 0.3-1. 5 mm. in length, and 18-90 /z in thickness at the base. The lateral rays of the same spicule are fairly equal or more or less unequal. Among the small hypodermal pentactines forms with equal lateral rays predominate, but among the large ones forms with unequal lateral rays are the more numerous. The lateral rays are more or less oblique and enclose angles of 80°-88° with the apical (proximal) ray. They are usually somewhat curved, conic, and rounded at the end. The longest lateral ray is 0.25-1.3 mm. long. The ends of the lateral rays (Plate 41, fig. 9) are, as in Hyalonema obtusum, usually irregular, and proba- bly for the same reason (c/. p. 160). In the forms B, C, and D, in which the greater part of the dermal membrane is lost, only few hypodermal pentactines were found. All those observed in forms C and D were similar to those of form A. In form B spiny pentactines * of similar dimensions were found, in addition to the ordinary smooth ones of the other forms. For the reasons given below (p. 183) I consider these spiny pentac- tines as foreign spicules. HYALONEMA (HYALONEMA) AGASSIZI. 183 The hexactine megascleres of form A (Plate 45, figs. 6-13) measured were 0.4-6 mm. in maximum diameter. The rays of the same spicule are in the smaller ones either equal or unequal, in the largest ones always unequal in length, two opposite ones being in these much longer than the other four. The four shorter rays are often also unequal among themselves. The rays arise from a central thickening 30-90 m in diameter, are smooth, conic, 10-58 m thick at the base, and blunt or rounded at the end. They are in the small hexactines straight, in the large usually slightly curved. The longest ray is 220 ^-3.2 mm. long. The hexactines of forms C and D are similar. In form B I found, besides hexactines similar to those of form A, one 11 mm. in maximum diameter with rays 70 /j. thick at the base, and only slightly attenuated to the rounded ends. In this form also spined hexactines, 2-5.5 mm. in diameter, occur. Although these are quite numerous and found in the depth of the choanosome, I do not believe that they really belong to the sponge. They are, like the large spined pentactines referred to above, identical with the spined hexactine and pentac- tine megascleres of Calycosilva cantharellus (Plate 1, figs. 5-24; Plate 6, figs. 1-12), a large number of specimens of which were trawled at the same station. Some of the spined hexactines and pentactines of these sponges may therefore have got accidentally into the sponge. In the basal part of the body, from which the stalk arises, slender acantho- phores, usually with four, more rarely with five or six rays (Plate 42, figs. 49, 51- 59), are met in all the forms except E and F. In form A these spicules (Plate 42, figs. 49, 51, 52) are 95-170, usually 110-135 m in diameter, and generally consist of four rays lying in the same plane and enclosing angles of 90° with their neigh- bours. Sometimes a fifth ray, vertical to the other four, is present. The rays of these spicules are fairly straight, at the base 2.5-4 ^ thick, rarely 5 /j., conic, and sharp-pointed. They bear numerous slender oblique spines inclined towards the tip of the ray. The largest spines are 4-12 ^ long. In form B these spicules (Plate 42, figs. 53, 54) are similar, measure 85-150 /x in diameter, and have rays 2-4.5 n thick at the base. Here only tetract.ines were observed. In form C these spicules (Plate 42, figs. 55, 56, 58) are larger, 120-210 n in diameter, and have four or, more rarely, five fairly straight or considerably curved rays, 3.5-5 m thick at the base. In form D some of these spicules (Plate 42, figs. 46, 57, 59) attain a still larger size. They measure here 100-230 n in diameter and have usually five, more rarely four or six rays 2.8-6 m thick at the base. Transitional forms were found quite frequently in the basal part of the 184 HYALONEMA (HYALONEMA) AGASSIZI. sponge-body, particularly in form C, apparently connecting these slender-rayed acanthophores with the modified basal pinules described above on the one hand, and the stout acanthophores described below, on the other hand. The stout acanthophores surrounding the proximal end-parts of the large stalk-spicules (Plate 45, figs. 1-4, 14-17, 24, 25, 35-39) are mostly tetractines and diactine tetractine-derivates. However, similar pentactines, triactines, and, exceptionally, also monactines occur among them. Occasionally one meets with tetractines and pentactines of this kind with all the rays greatly reduced in length. These spicules appear as transitions, leading to the spheres described below. The rays of the same spicule are always more or less, and sometimes very unequal. They generally join at angles of about 90° or 180°, and are straight or curved, and cylindrical and terminally rounded, or conic and either blunt or pointed at the end. The diactine ones are either centrotyle or simply cylindrical in the centre, straight, slightly angularly bent in the middle, or, rarely, strongly curved. One 11 m thick, which I observed in form A, formed a complete ring 65 m in diameter. Sometimes the rays bear rudiments of branch-rays. The basal parts of the rays are usually smooth or only sparsely spined ; their end-parts bear numerous, rather large, generally nearly vertical spines, which stand close together. The smooth proximal part is usually a little longer than the spined distal part. In form A the larger, normal acanthophores are 200-690 m in maximum diameter and have rays 14-40 n thick at the base. The small ones transitional to the spheres (Plate 45, figs. 24, 25, 38) are 46-115 in diameter and have rays 9-14 /x thick. In the other forms these spicules appear to be similar. Form D possesses mon- to pentactine spicules of this kind 195-550 ^ in maximum diameter with rays 15-35 /x thick. The monactines are very rare. One that I measured was 195 n long, and at the rounded, somewhat thickened end, 12 ^ in transverse diameter. In the preparations of one of the specimens of form F the stout acanthophores are particularly numerous. The triactine and tetract.ine forms here measure 120-640 /x in diameter, usually 420-590 /x, and have rays 20-40 m thick at the base. The diactine forms are usually fairly straight, rarely strongly angularly bent in the middle so that the two rays enclose an angle of 90° or less. The fairly straight diactines are 120-550 m long. Their rays have the same thickness as those of the triactines and tetractines. HYALONEMA (HYALGNEMA) AGASSIZL 185 In the spicule-preparations of the basal part of this form numerous small, hollow, cross-like siliceous bodies were observed. The smallest of these are about 20 n in diameter, and consist of four somewhat conic rays, 10 ^ long, about 16 m thick at the base, and hollowed out by cylindrical axial canals about 8 m wide. These smallest crosses are connected with the large normal stout-rayed tetractines above described by an uninterrupted series of spicules intermediate in size. The axial canals of these spicules are usually 5-9 n wide. The axes of the rays of the full-sized, stout-rayed basal spicules are occupied either by a fine axial thread, or a more or less widened axial canal. The broadest axial canals in these spicules were about 9 /x in diameter. In cylindrical, terminally rounded rays these axial canals are closed at the end; in conical and pointed rays they usually open out freely. The wide axial canals are regular or irregular. The regular ones are either cylindrical throughout or widened distally. Distal widenings occur both in the terminally open and in the terminally closed axial canals. The irregular ones are of two kinds. In some the axial canals bear short, irregular, branch-like diverticula, which usually arise near the distal end, and are vertical or oblique, directed outward or, more rarely, inward. Others possess backwardly directed diverticula, which arise from their basal part and occupy interstices between adjacent silica-layers. It is obvious that the small forms of this series are to be considered either as the young of the full-sized ones, or as the last remnants of full-sized ones which have in great part been dissolved. The general appearance of the whole series seems to me to be in favour of the latter alternative. I accordingly assume that the stout acanthophores with wide axial canals are spicules in process of decay (solution), that this decay or solution is the further advanced the smaller the spicules are, and that the dissolving agency acts on the silica-layer both from the inner (the axial threads) and the outer side (the surface). No doubt the sea- water can and does dissolve the silica of the spicule in this way when the protect- ing organic or semiorganic sheath is lost, but it must not be overlooked that the living sponge-tissue of the sponge itself might possibly also attack and dissolve the silica in spicules which have become superfluous, and use the material thus obtained for building up other spicules. The spheres of form A (Plate 45, figs. 26-34) are irregularly nodular or spherical and measure 18-57 n in diameter. Most of them are smooth (Plate 46, figs. 26-29, 33, 34), some more or less spiny (Plate 45, figs. 30-32). They consist of concentric layers of silica. The centre around which these silica-layers are 186 HYALONEMA (HYALONEMA) AGASSIZI. deposited may be a simple point, a short rod, or a cross. The spheres with a cross-shaped centre (Plate 45, fig. 29) lead to those short-rayed tetractines (Plate 45, figs. 24, 25) which have been referred to above as transitions between the normal long-rayed, stout, basal spicules and the spheres; I am inclined to consider the spheres as derivates of these spicules. I have not seen any spheres in the preparations of form B and C, but I found some, similar to those of form A, in form D. The microhexactines and their derivates form a series commencing with regular equal-rayed hexactines and ending with diactines and monactines. They fall into two groups : — 1 , regular and irregular microhexactines proper, and 2, diactine and monactine microhexactine-derivates. The microhexactines -proper (Plate 44, figs. 15, 16, 17b, 18-23, 25-30) have regularly disposed rays which enclose angles of 90° with their neighbours. The rays are conic and pointed. Their basal part is straight, their distal part nearly straight or curved more or less, sometimes considerably. In the forms E and F, where the microhexactines with the most strongly curved rays are found inter- mingled with the other, more straight-rayed forms, the degree of curvature appears to be in inverse proportion to the size of the spicule. The end-parts of opposite rays are usually curved in opposite directions. The rays of these spicules are beset with small backwardly directed spines. These are largest and most numerous on the middle-part of the ray; proximal ly they decrease in number, distally in size. It is also to be noted that these spines are on the whole much larger in the large (and straight-rayed) than in the small (and more curved-rayed) microhexactines. The microhexactines proper of form A (Plate 44, figs. 16, 17b, c, 18-20, 22, 23, 30) are 50-144 /x in diameter and have rays 1.7-4 m thick at the base. The irregular forms are larger (longer) and have thicker rays than the regular. The difference in the length of the rays of the irregular forms is sometimes very con- siderable, the length of the shortest ray being occasionally only a ninth of that of the longest. In the other forms the microhexactines proper are similar and also in these the irregular ones are larger than the regular. The maximum diameter of the microhexactines proper measured was in form B (Plate 44, figs. 21, 25, 27) 66-145 /x, in form C (Plate 44, fig. 26) 44-130 m, in form D (Plate 44, figs. 28, 29) 48-114 fx, in form E 53-157 /x, and in form F 52-160 /x. The diactine and monactine microhexactine-derivates are by no means fre- quent. The diactine microhexactine-derivates of form A (Plate 44, fig. 24) are HYALONEMA (HYALONEMA) AGASSIZI. 187 more or less centrotyle spiny rods, pointed at both ends. Their middle-part is straight, their end-parts are slightly curved. These spicules are 84-240 n long and 3.6-5 m thick near the centre. The central tyle measures 5.8-15 /x in trans- verse diameter and, when large, clearly shows that it is composed of four ray-rudi- ments. The monactine microhexactine-derivates are very rare. One of form A which I measured was 75 /x long, and 3.5 ^ thick at the rounded end. Apart from the diactine pinules and the diactine and monactine derivates of the stout-rayed basal tetractines and the microhexactines above described, three kinds of rhabds can be distinguished : — ordinary rliabds of the choanosome and axial column, modified rhabds of the basal part of the sponge-body, and uncinates. The ordinary rhabds of the choanosome and axial column (Plate 45, figs. 19- 22) are smooth, slightly curved or, rarely, angularly bent, 0.3-7 mm. and more long, as some long fragments observed indicate, and 7-50 n thick, rarely 95 /x. Most of them are blunt amphioxes or amphistrongyles, but amphityles, styles, and t.ylostyles also occur among them. The smaller amphioxes, amphistrongyles, and amphityles are generally distinctly centrotyle. Remarkably regular cylin- drical amphityles occur in the marginal part of the gastral wall of form A. These are mostly 0.7-1 mm. long and 26-30 n thick; their spherical terminal tyles measure 40-50 ^ in diameter. A short somewhat spindle-shaped style 75 /x thick at the rounded end and 95 /x at the stoutest point was observed in the axial column of this form. The axial canals (threads) of the small rhabds are usually quite fine, those of the large ones on the other hand generally wide, sometimes 5 /x or more in transverse diameter. The modified basal aca,nthopliore rhabds (Plate 45, fig. 5) are centrotyle, usu- ally slightly curved, smooth in the middle, and strongly spined at the ends, which are generally somewhat thickened. The terminal thickenings are either spheri- cal or spindle-shaped, and in the same may be either similar or dissimilar, one end-thickening frequently being spherical, the other spindle-shaped. These spicules are 0.8-2. 6 mm. long, and 7-22 ^ thick near the centre. The central tyle is 12.5-27 m in transverse diameter, the terminal thickenings 12-30 /x. The spherical terminal thickenings are stouter than the spindle-shaped. The spiny end-parts are 80-260 n long. The axial canals (threads) of these spicules are often very wide. They are usually closed in the rounded ends and open in the spindle-shaped. The uncinates are mostly diactine, but monactines also occur. 188 IIYALONEMA (HYALONEMA) AGASSIZI. The diactine uncinates (Plate 44, figs. 6-14, 17a) are generally straight or slightly curved, simple amphioxes; considerably curved and centro tyle ones, however, also occur. The ordinary amphiox uncinates in form A are 330-800 n long, 5.5-12 n thick in the middle, and beset with spines. As far as I could make out these spines are 0.7-1. 5 n long, and about 1 n thick at the base. Sometimes it appeared as if they were continued in a fine terminal filament which was, however, too thin to be distinctly projected even with the 280 ^ light. At one end of the spicule these spines are numerous, rather close together, and strongly inclined toward the opposite end. Toward the other end they become much scarcer and less inclined. Some of the spines nearest the latter end are vertical or even inclined in the opposite direction. In the centrotyle uncinates the cen- tral tyle is 15% to 45% thicker than the adjacent parts of the spicule. The monactine uncinates appear as tylostyles. In form A they are 260- 293 m long and 9-12 n thick just below the rounded end. The rounded end itself is thickened to a more or less spherical tyle 14-16 n in transverse diameter. The large stalk-spicules of form A (Plate 41, fig. 2; Plate 43, figs. 1-7) have a maximum length of 42 cm. and all are broken off at the lower distal end. Where they arise from the sponge they are 0.05-0.95 mm. thick; 30 cm. lower, where most of them are stoutest, they are 0.5-1. 3 mm. thick. One (Plate 43, fig. 1), which I studied in detail, is 160 m thick at the upper end, and rapidly increases in thickness to 730 n at 7 cm. from the end; it then gradually thickens down to 28 cm., where it attains its maximum thickness of 1050 fx. Farther on it again becomes thinner, and at the lower end, 42 cm. from the tip, is 760 p thick. Its axial thread is for the most part thin. It is thickened, however, here and there in an irregular manner. The silica is very clearly stratified. The surface of the upper, proximal part of the spicule is quite smooth. Where the spicule attains its maximum thickness fine transverse lines (Plate 43, fig. 7) make their appearance on its surface, and 1 cm. above the distal end its surface, for a short distance, has quite a peculiar structure (Plate 43, fig. 4). Here a silica-layer is exposed which consists of lamellae overlapping like tyles, and composed of parallel rods about 10 n thick and lying close to- gether. These rods extend nearly but not quite paratangentially and longitudi- nally. They deviate slightly both radially and laterally from the direction of the axis of the spicule. The radial deviation is due to their forming the overlapping lamellae, and like the lamellae themselves they slightly diverge from the axis below. The lateral deviation is due to their lying somewhat obliquely in elon- gated spirals. HYALONEMA (HYALONEMA) AGASSIZI. 189 Most of the other stalk-spicules exhibit, in their lower portion, the same transverse lines as the one described above, and in six of them the same spiral rods, combined to form tyle-like lamellae, are visible on portions of the surface near the end. The transverse lines may be considered as fissures in the superficial silica- layer. In the six spicules where it was observed, (and probably also in the others) the portions showing the superposed rows of spiral rods indicate that there are one or more silica-layers (composed of thin, spirally extending rods) quite different in structure from the rest. These layers are rendered visible where the disintegration (solution) of the spicule (which proceeds from the surface downwards) has just reached them; and their structure is probably brought out so clearly by the silica joining the rods having been partly dissolved. Being composed of layers differing in structure, one or more of which consist of superimposed rows of spirally arranged rods or threads, the stalk-spicules may, in respect to their internal structure, be compared to cables. No traces of backwardly directed spines or of terminal anchors could be found in any of the spicules. The amphidiscs (Plate 44, fig. 17d; Plate 45, figs. 40-G4; Plate 46, figs. 1-16; Plate 47, figs. 1-13). The biological length frequency-curve of the amphidiscs of Hyalonema agassizi, form A, shows (Fig. 5), that, as regards the frequency of those of different length, these spicules fall, like those of Hyalonema obtusum, into four groups: — large macramphidiscs, small macramphidiscs, large micram- phidiscs, and small micramphidiscs. The second and third of these groups are, in respect to their length frequency, not as clearly distinguished from each other as from the first and fourth respectively. The parts of the curve pertaining to the large macramphidiscs and the small micramphidiscs each have two culmi- nations, a principal, and a secondary. The measurements and examination of the amphidiscs of various length of the three other forms show that these also fall into the four groups mentioned, and that, at least in two of them (B and C), the gap between the small macramphidiscs and large micramphidiscs is not so distinct as in the others. In the forms B and C these two kinds of amphidiscs, which can be readily distinguished by differences in their shape, slightly overlap in respect to their length. The large macramphidiscs of form A (Plate 46, figs. 2-5, 9, 12, 13; Plate 47, figs. 1, 2, 5, 6, 10) are 134-242 n long, most frequently about 200 //. The shaft is straight, cylindrical, 7-13.5 m thick, and thickened abruptly at some point 190 HYALONEMA (HYALONEMA) AGASSIZ1. Fig. 5. — Form A. Amphidiscs. near its centre to 8-20 n, and gradually at both ends to 8-15 n. From the central thickening arises a regular, or irregular, verticil of conic truncate spines which is 2-8 m long, and 2-5 n thick at the base. The ends (terminal faces) of these spines bear clusters of small secondary spinelets. The other parts of the shaft usually bear a few, rarely a good many, very low protuberances covered with clusters of secondary spinelets. These protuberances are circular in outline and agree in breadth and secondary spinulation with the spines on the central thickening. The shaft is traversed by a fine axial thread which, where it passes through the central thickening, is slightly thickened to a small but well-defined point. Traces of branch-rays of the axial thread (an axial cross) could be detected neither here nor elsewhere. The terminal anchors are composed of eight to twelve recurved teeth. They are 40-80 n in length, that is about a third, generally a little less than a third, of the whole spicule, and 41-86 /x broad. The proportion of the length to the breadth of the anchors is 100 to 91-120, on an HYALONEMA (HYALONEMA) AGASSIZI. 191 average 100 : 103. The anchor-teeth are T-shaped in transverse section. The upper part appears as a curved band, for the greater part of its length 8.7-11.5 n broad, and attenuated to a point or, more rarely, rounded off at the end. The teeth arise steeply and are uniformly curved, concave to the shaft. The curva- ture is not very great and never suffices to give the end-parts of the teeth a direction parallel to the shaft. The tangents on these end-parts enclose, in the adult large amphidiscs, angles of about 5° with the axis of the shaft. In young spicules of this kind (Plate 46, fig. 9) this angle is, of course, much greater. The large macramphidiscs of form B (Plate 46, fig. 15) are 126-310 /x long, most frequently about 240 fx. Their shafts are 8-14 m thick, and their anchors are 46-67 /x long and 48-76 /x broad. These spicules are longer and have smaller anchors than those of form A. The large macramphidiscs of form C (Plate 46, figs. 10, 11) are 110-290 n long, most frequently about 240 n. Their shafts are 6-10 n thick, and their anchors 40-63 /x long and 35-75 /x broad. They are very similar to those of form B, and are like them longer and provided with smaller anchors than those of form A. The large macramphidiscs of form D (Plate 46, figs. 6-8, 16) are mostly regular and similar to those of the other forms. They are 132-282 n long, most frequently either about 240 or 180 n, with shafts 9.5-12 n thick, and with anchors 52-73 m long and 48-66 /x broad. In respect to their length the regular large macramphidiscs of form D are intermediate between forms B and C on the one hand and form A on the other. Their anchors are similar in size to those of forms B and C. In the specimen of form D I found an irregular large macram- phidisc (Plate 46, fig. 7) 192 /x long, with a shaft 4.4 /x thick. The two anchors of this spicule are both about 26 /x broad but very unequal in length, one being 44 n long, the other considerably shorter. The shaft is beset with numerous large pointed spines, all strongly bent towards one end. These spines increase in size towards the end from which they diverge; the largest is 16 n long. The large macramphidiscs of form E are 150-280 n long, usually 170-256 n, most frequently about 200 fx. Their shaft is 6-12 /x thick. Their anchors are 51-67 ix long and 51-80 /x broad. The large macramphidiscs of form F are 112-260 m long, usually 150-232 n, most frequently about 200 n. Their anchors are 36-65 ix long and 34-70 m broad. In a preparation of one of the specimens of this form I found an ab- normal large macramphidisc, in which the central spine- verticil was replaced by an anchor similar to but slightly smaller than the terminal anchors. 192 HYALONEMA (HYALONEMA) AGASSIZI. To attain a clearer insight into the range and character of the variation of the length of the large macramphidiscs in the four forms of this sponge I drew the following graph, in which the frequency of the large macramphidiscs of various lengths of all the four forms is represented. To make the curves in it commensurate I calculated the relation of the number of large macramphidiscs actually measured to 100, that is its percentage in each form, and multiplied all the numbers of amphidiscs belonging to the same category, in respect to length, by this number. These percentages are represented by the curves in Fig. 6. Fig. 6. — - Large macramphidiscs. The above curves, expressing the relative frequency of the large macramphi- discs of different lengths in the six forms, are based on 247 measurements. The curves pertaining to all the forms, except D, have one main elevation, the curve pertaining to form D has two. The second main elevation of this curve coin- cides with the main elevations of the curves of forms B and C, and with the considerable right secondary elevation of form E. All four lie at a point corre- sponding to amphidiscs about 240 m long. The main elevations of the curves of forms A, E, and F lie at points representing spicules about 200 m long. The HYALONEMA (HYALONEMA) AGASSIZI. 193 first elevation of the curve of form D corresponds to still shorter amphidiscs, of about 180 /d in length. The curves of forms A, D, and F have a small secondary elevation at about 290 n. The curve of form B has a secondary elevation at about 164 n] the curve of form F has also an additional slight secondary eleva- tion at about 112 /*. These curves indicate that A, E, and F have, on the whole, smaller large macramphidiscs than the other forms; that D possesses two nearly equally numerous varieties of these spicules, a larger and a smaller one; and that in C the small forms of the large macramphidiscs are much rarer than in the others. They further show that the large macramphidiscs of all the six different forms differ in respect to the character and range of the variation of their length. It is also to be noted that none of the curves are similar to a mathematical proba- bility curve; for these spicules do not, in respect to their length, vary uniformly round a mean. The small macramphidiscs of form A (Plate 46, fig. 1) are 62-115 p long, most frequently about 93 n, and have a cylindrical centrotyle shaft 3-8 n thick. The central thickening bears a verticil of rather blunt spines 1.3-1. 5 n long and about 0.5 fx thick. Numerous similar spines are found on the other parts of the shaft. The anchors are 22-43 m long, that is about a third, generally a little more than a third, of the whole spicule, and are 16-42 n broad. The proportion of their length to their breadth, in the smaller forms under 80 n in length is, 100 to 73-84, on an average 100 : 79; in the larger forms, over 80 n in length, it is 100 to 76-105, on an average 100 : 90. The shape of the individual anchor-teeth is, on the whole, similar to that of those of the large macramphidiscs; but it is to be noted that their curvature, in the smaller forms of these spicules, is considerably greater. In the specimen of this form (A) I found a remarkable hexactine spicule 116 n in diameter, composed of four fully developed and two rudimentary rays. The four developed rays are cylindrical, 7.5 n thick, and bear at their ends verticils of large recurved teeth which together form somewhat irregular anchors 36 n long and about 64 n broad. One of the rudimentary rays is a short, terminally rounded cylinder; the other is bifurcate and slightly longer at the end. The whole spicule appears as a cross formed by two small macramphidiscs joined in the middle, from the centre of which two protuberances arise. Spicules of this kind have occasionally, but very rarely, been observed in other species of Hyalonema, as H. tenerum.1 The only hyalonematid in which 1 F. E. Schulze. Rept. Voy. Challenger, 1887, 21, pi. 31, fig. 18. 194 HYALONEMA (HYALONEMA) AGASSIZI. they are more abundant is Monorhaphis dives,1 where they usually have six anchor-bearing rays. F. E. Schulze iloc. cit.) named these spicules hexadiscs. The spicule above described and others similar, like the one found in Hyalonema tenerum ( loc . cit.), might, in an analogous manner, be called tetradiscs, or stauro- discs. In the other forms of Hyalonema agassizi only a few small macramphidiscs have been observed. Those seen were similar but smaller than those of form A. The small macramphidiscs of form B (Plate 45, fig. 53) are 53-101 n long. Their shafts are 2-4 p thick, and their anchors 18-27 /x long and 18-33 n broad. Those of form C are 53-80 /x long. Their shafts are 2-3.3 n thick, and their anchors 20-24 p long and 16.5-20 m broad. In form D only a single small macramphi- disc was found. This was 84 p long. In form E the small macramphidiscs are 48-90 /x long, most frequently about 51 m, and have anchors 10-33 m long and 10-25 /x broad. In form F I found only two such spicules. These were 45 and 70 n long respectively. In form A the large micramphidiscs (Plate 45, figs. 46-49; Plate 47, figs. 11- 13) are very numerous. They are here 42-60 /x long, most frequently about 52.3 ii. The shaft is 1.1-2 /x thick, cylindrical, or slightly and very gradually thickened, in a spindle-shaped manner, in or near the middle, but without a sharply defined central tyle. It is covered with numerous, slender, cylindrical, vertical or, more rarely, oblique spines, sometimes 2 n long. The anchors are relatively slender. They are 14.4-22 p long, that is a little more than a third of the whole spicule, and 8-14 m broad. The proportion of their length to their breadth is 100 : 53 (in one of the smallest), 100 : 71 (in one of the largest), on an average 100:65. The individual anchor-teeth are about 1.5 /x broad and strongly curved, so that their end-parts lie nearly parallel to the shaft or converge towards it. In form B, where they are rather scarce, the large micramphidiscs appear to be similar to those of form A, and measure 41-59 m in length, most frequently about 54.8 p. In form C (Plate 45, figs. 59-61), where they are still more numerous than in form A, they measure 36-64 p in length, most frequently, as those of form A, about 52.3 p in length, and have spinecl shafts 1-1.7 m thick. Their anchors are 17-23 m long and 10-13 /x broad. One in which I was able to count the anchor- teeth had fourteen. The individual teeth in the larger forms are about 2.5 ^ broad. 1 F . E. Schulze. Hexactinellida. Ergeb. Deutsch. t.iefsee-exped., 1904, 4, p. 124, taf. 43, figs. 1, 6, 7. HYALONEMA (HYALONEMA) AGASSIZI. 195 In form D, where they are also rather frequent, the large micramphidiscs (Plate 45, figs. 63, 64) measure 35-55 ^ in length, most frequently about 47.5 ij. Their shafts are spiny and 1.5-1. 7 ij thick; their anchors are shorter than in the other forms, 15-17 n long, and 10-11 n broad. In the specimens of form E the large micramphidiscs are exceedingly abun- dant. They are here 40-69 m long, most frequently about 48 ij, and have anchors 13-21 ij long and 8-14 ^ broad. In the specimens of form F the large micramphidiscs are not nearly so numerous. They are here 37-57 m long, most frequently about 52 /x, and have anchors 14-20 /j long and 9-14 ^ broad. According to the frequency of those of different length, three kinds of small micramphidiscs can be distinguished in form F, and two kinds in forms A, B, C, and E. The small micramphidiscs of form D are all of the same kind. The smaller (A, B, C, E) or smallest (F) kind is invariably the most abundant. The spicules belonging to the larger (A, B, C, E) or largest (F) kind have very slender anchors and appear as transitions between the (broad-anchored) small and the (slender-anchored) large micramphidiscs. Judged morphologically, by their shape alone, the larger (largest) kind of small micramphidiscs should, indeed, be considered as belonging to the large micramphidiscs. Since, however, in the smaller (A, B, C, E) or smallest and intermediate (F) kinds of small micram- phidiscs the relative breadth of the anchors decreases with the increase in the size (length) of the spicules, since in a few exceptional spicules of this kind the anchors are quite as slender as in the larger (largest) kind, and since they are, in the forms where they occur, separated biometrically much more clearly from the larger micramphidiscs than from the smaller kind of the small micramphi- discs, I provisionally place them in the latter group. The small micramphidiscs of form A (Plate 44, fig. 17d; Plate 45, figs. 40- 45; Plate 47, figs. 3, 4, 7-9) are 15-36 /j long, most frequently about 18.3 /j. The limit between the larger and the smaller kind lies at about 29 The shaft is straight or rarely bent, 0.6-1. 4 /j thick, cylindrical throughout, or slightly and gradually thickened in the middle. It is either quite smooth, or it bears near the centre an irregular cluster of a few spines, not over 0.5 /j long, or it is covered with sparse, vertical, more rarely oblique, spines throughout. The anchors are 4-13 m long, that is a quarter to a third of the whole spicule, and 4.7-9 ^ broad. They consist of fifteen or sixteen recurved teeth. In the larger kind of small micramphidiscs the proportion of the length to the breadth of the anchor is 100 to 58-75, on an average 100 : 64; in the smaller kind 100 to 75-135, on an 196 HYALONEMA (HYALONEMA) AGASSIZI. average 100 : 93. It is to be noted that in the smaller small micramphidiscs the relative breadth of the anchor is, on the whole, in inverse proportion to their size (length) . The curvature of the individual teeth is such that the anchors appear rather broad above and that the end-parts of the teeth come to lie parallel or nearly parallel to the shaft. The small micramphidiscs of the other forms appear to be very similar to those of form A. Those of form B (Plate 45, figs. 50-52) are 13.5-31.5 /x long, most frequently about 20.1 m- The limit between the larger and smaller kinds lies, as in form A, at about 29 Those of form C (Plate 45, figs. 54-58) are 14-30 ju long, most frequently about 18.3 n. The limit between the larger and the smaller kind lies here at about 25.5 /x. Those of form D (Plate 45, fig. 62) are 13-28 m long, most frequently about 20.1 n. The small micramphidiscs of form E are 15-34 ju long, most frequently about 22.2 /x. The limit between the larger and smaller kind lies at about 24.4 /j. . The small micramphidiscs of form F are 15-33 m long, most frequently about 18.3 /i. The limits between the smallest, the intermediate, and the largest kind of small micramphidiscs of this form lie at about 20.2 n and 25.4 /x- To obtain a clearer insight into the range and character of the variation of the length of the small micramphidiscs in the four forms of this sponge I Frequency Fig. 7. — Small micramphidiscs. HYALONEMA (HYALONEMA) AGASSIZI. 197 drew (by the method already described) Figure 7, in which the relative frequency of the small micramphidiscs of various lengths of all the four forms is represented. The above curves, expressing the relative frequency of the small micramphi- discs of different lengths in the six forms, are based on 381 measurements. All have one main elevation; those of forms A, C, and E have one secondary eleva- tion, the curves of forms B and F have two. The main elevations of the forms A, C, and F correspond to amphidisc-lengths of about 18.4 m, those of forms B and D to amphidisc-lengths of about 20.1 those of form E to amphidisc- lengths of about 22.2 n. The first and principal secondary elevation of form F, which is very con- siderable, coincides with the main elevation of form E at about 22.2 n. The first secondary elevation of form B, which is quite insignificant, lies at about 24.4 The first secondary elevation of form E and the second secondary elevation of form F, which are both very well-pronounced, lie at about 26.8 m- The single secondary elevation of form C, which is inconsiderable, is situated at about 29.5 n. The second secondary elevation of form B and the single secondary elevation of form A both lie at about 32.5 The former of these is very well-pronounced, the latter insignificant. These curves clearly show that the small micramphidiscs of forms A, C, and F are on the whole relatively small, those of forms B and D intermediate, and those of form E relatively large, and further that all the six forms differ in respect to the range and character of the variation of the length of their small micramphidiscs. The description given above shows these sponges to be so similar that there can be no doubt about their belonging to one and the same species. They differ, however, more or less by their external shape, the structure of their gastral cavity, and the shape and size of their spicules. The variable spicule-characters which could be accurately ascertained in a sufficient number of spicules in all the forms are: — the length and maximum thickness (together with the spines) of the distal ray of the dermal pinules and gastral cone-pinules, the nature of the spinulation of the former, the diameter of the microhexactines, and the length of the large macramphidiscs and small micramphidiscs. In the following discussion I have considered only these spicule-dimensions, the shape of the sponge, and its gastral cavity. The specimens from Station 4651 and 4656 and some of the specimens from Station 4742 are massive, spindle-, pear-, top-, or club-shaped, the specimens from 198 HYALONEMA (HYALONEMA) AGASSIZI. Station 3684 (A. A. 17) and Station 4740 and the other specimens from Station 4742 are flattened, cake-shaped. In the specimen from Station 4656 the gastral cavity is a narrow fissure, uninterrupted by radial plates; in all the specimens from Stations 4651 and 4740, in the cake-shaped specimens from Station 4742, and probably also in the specimen from Station 3684 (A. A. 17), the gastral cavity is quite wide and divided into separate diverticula by radial plates. The dermal pinules of the specimens from Stations 4656 and 4740 have longer distal rays than the others. The dermal pinules of the specimen from Station 4656 and the pear- shaped specimens from Station 4742 have more slender distal rays (together with the spines) than the others. The spines of the distal rays of the dermal pinules of the specimen from Station 3684 (A. A. 17) are more crowded and form a more compact structure than those of the others. The distal rays of the gastral cone- pinules are of five sizes. Those of the cake-shaped specimens from Station 4742 are on an average only 90.5 n long, those of the specimen from Station 4651 98.2 m, those of the specimen from Station 3684 (A. A. 17) 106.7 m, those of the specimens from Stations 4656 and 4740 128.2 m-128. 5 and those of the pear- shaped specimens from Station 4742 129 m long. Those of the specimens from Station 4740 are (together with the spines) narrower than the others. The microhexactines are relatively large in the specimens from Stations 4651, 4656, and 4742, smaller in the specimens from Station 4740, and still smaller in the specimen from Station 3684 (A. A. 17). In the specimens from Stations 4651 and 4740 the large macramphidiscs are of one kind and most frequently about 240 n long. In the specimens from Stations 4656 and 4742 these spicules may also be said to be of one kind, and they are here most frequently about 200 /x long. In the specimen from Station 3684 (A. A. 17) a smaller kind, most frequently about 180 m long and a larger kind most frequently about 240 /x are nearly equally abundant. The small micramphidiscs in the specimens from Stations 4656 and 4740 and the pear-shaped specimens from Station 4742 are most frequently about 18.3 ix long, those of the specimens from Stations 4651 and 3684 (A. A. 17) most frequently about 20.1 /x, and those of the cake-shaped specimens from Station 4742 most frequently about 22.2 /x. This shows that the specimens of this species differ in respect to the follow- ing ten accurately determinable qualities: — a, the external shape, 6, the nature of the gastral cavity, c, the length of the distal rays of the dermal pinules, d, the maximum thickness of the distal rays, together with the spines, of the dermal pin- ules, e, the density of the spinulation of the distal rays of the dermal pinules, /, the length of the distal rays of the gastral cone-pinules, g, the maximum thickness HYALONEMA (HYALONEMA) AGASSI ZI. 199 of the distal rays, together with the spines, of the gastral cone-pinules, h, the diameter of the microhexactines, i , the length of the large macramphidiscs, and k, the length of the small micramphidises. The following table, arranged in pairs, shows which of these qualities the forms A to F have in common. 4656 (A) and 4651 (B) 4 a e g h “ “ 4740 (C) 4 c e f k c 0 “ “ 3684 (A.A. 17) (D) 1 g c3 “ 4742 cake-sh. (E) o c-; 4 e g h i 45 m “ 4742 pear-sh. (F) 7 a b d e g h k £ 4651 (B) and 4740 (C) o 4 b d e i o “ “ 3684 (A.A. 17) (D) o CD 5 m 0 b c d g k m £ “ 4742 cake-sh. (E) Oh cn CD 6 4-5 b c d e g h a “ 4742 pear-sh. (F) 5 O a c e g h ’o 4740 (C) and 3684 (A.A. 17) (D) 0 3 a b d a m “ “ 4742 cake-sh. (E) 43 “ 4742 pear-sh. (F) bfi c3 1 e H 3684 (A.A. 17) (D) and 4742 cake-sh. (E) 5 a b c d g “ 4742 pear-sh. (F) 4 c g i k 4742 cake-sh. (E) and 4742 pear-sh. (F) 4 oegh These affinities are shown in Figure 8. Of the five stations where these sponges were trawled, two, Stations 4651 and 4656, lie near together off the Peruvian coast. The other three, Stations 4740, 4742, and 3684 (A.A. 17), are a considerable distance apart in the central Pacific and are far from the two Peruvian stations. The degree of similarity of the specimens separated as the six kinds of Hyalonema agassizi stands in no relation to the distances of their localities from each other. Thus the cake- and the pear-shaped specimens from Station 4742 agree only in respect to four of the ten qualities, and the pair from Stations 4651 and 4656, which lie very near each other, also agree only in respect to four qualities. The pairs which agree most are the pear-shaped specimens from Stations 4656 and 4742, which agree as to seven qualities, and the cake-shaped specimens from Stations 4651 and 4742, which agree in respect to six. The units of the pairs of stations from which these come are very far apart. These and the other differences between the six kinds of H yalonema agassizi are not systematically important individually; I believe, however, that several of them together demand recognition. Of the ten varying qualities here under discussion, nine are different only in two pairs from Stations 4656, 3684 (A.A. 17), and Stations 4740, 4742 pear-shaped. All the other pairs differ by from three to seven of these qualities. Since the units of the two mentioned strongly diver- gent pairs are connected in other ways, and since, as has been shown above, there appears to be no correlation between the degree of difference and the distance of the localities, I do not think that these differences warrant the 200 HYALONEMA (HYALONEMA) AGASSIZI. establishment of separate varieties. The distinction of different forms within the species, designated A, B, C, D, E, and F, is a sufficient division. The species composed of these six forms is most closely allied to the Hya- lonema ( Hyalonema ) obtusum and the Hyalo7iema ( Hyalonema ) polycaulum. The outer appearance of the variety gracilis of H. ( H .) obtusum is indeed nearly the same as that of form A. These latter differ, however, from H. (H.) obtusum in the following respects : — the dermal pinules are considerably longer in both varieties of H. (H.) obtusum than in any of the forms described above; the HYALONEMA (HYALONEMA) POLYCAULUM. 201 slender-rayed basal spicules are about twice as large, and the microhexactines are smaller, and composed of more strongly curved rays in the former than in the latter; the large macramphidiscs of 77. (II.) (Muslim reach 356 m in length, have shafts bearing large spines along their whole length and possess anchors the end-parts of whose teeth are parallel to the shaft; the large amphidiscs of II. (. H .) agassizi are not over 310 n long, have shafts destitute of large spines outside the centre, and possess anchors the end-parts of whose teeth diverge ; the end- parts of the anchor-teeth of the large micramphidiscs are in the former far more curved than in the latter. Hyalonema ( Hyalonema ) polycaulum is in outer appearance, apart from its polycaule nature, similar to the forms described as C, D, and E. It differs from this species, however, by its large macramphidiscs, its pinules, and its mode of attachment to the sea-bottom. The large macramphidiscs are in the sponges described above considerably shorter, have relatively narrower anchors and anchor-teeth much more strongly curved in their distal part and less divergent, than in Hyalonema ( Hyalonema ) polycaulum. The distal rays of the pinules of the former are considerably thickened above the middle and have a stout terminal cone. In those of the latter such a thickening above the middle is either absent or very insignificant, and the terminal cone is much more slender. It is also to be noted that the distal rays of the pinules of the sponges described above bear more numerous spines than those of Hyalonema ( Hyalonema ) poly- caulum. The former is attached by a single stalk; the latter by several stalks. Hyalonema (Hyalonema) polycaulum, sp. nov. Plate 53, figs. 1-17; Plate 54, figs. 1-45. One specimen of this species was trawled in the eastern part of the Tropical Pacific at Station 4721 on 15 January, 1905; 8° 7.5' S., 104° 10.5' W. ; depth 3811 m. (2084 f.) ; bottom composed of light brown Globigerina ooze. It appears to have possessed four distinct stalks. To this the specific name refers. Shape and size. The single, somewhat fragmentary specimen (Plate 53, fig. 4) is oval, 54 mm. long, 48 mm. broad, and somewhat flattened. Only slight remnants of the dermal membrane are left, the specimen appearing very porous in consequence. A group of large cavities, separated by thin plates, occupies one of the flat faces. A thickening at the joining line of these plates, which, however, does not project freely, is, as its internal structure shows, a gast.ral cone. The large cavities around it are parts (diverticula) of the gastral cavity. On the 202 HYALONEMA (HYALONEMA) POLYCAULUM. opposite flat face of the sponge the superficial tissue is, in four places, consider- ably harder than elsewhere. These harder patches protrude more or less and appear as superficial knobs. They are distant from each other and rather uni- formly distributed over the face opposite the gastral. From two of these knobs a few broken stalk-spicules protrude. The colour in spirit is brown. Skeleton. Of the dermal pinule-fur only insignificant remnants are left; the gastral pinule-fur, however, is preserved in places. The dermal pinules have much shorter lateral rays than the gastral. Here and there, where the super- ficial parts of the sponge are still present, pentactine megascleres occur. The hard superficial knobs contain dense masses of t.etractine (tetractine-derivate) stout, and diact.ine (diactine-derivate) more slender acanthophores. Here also slender-rayed, long-spined acanthophores are met. Large quantities of micro- hexactines, some microhexactine-derivates with fewer than six rays, and a good number of more or less pinule-like pentactines, which may be tubular pinules, and amphidiscs occur in the choanosome rhabd and hexactine megascleres. Certainly from two, probably from all the four hard superficial knobs bundles of rather large spicules, broken off at the surface of the sponge, extend towards the interior. One of these bundles leads up to the gastral cone above referred to. The spiculation of these knobs indicates that certainly from two and probably from all four there arise in life stalks composed of bundles of spicules. A good many anatriaenes with long and slender anchors, very large dicho- triaenes, and large spiny metasters, all foreign, and apparently belonging to some species of Thenea, are found in the sponge. A few hexactinellid anchor- spicules, similar to those of the holascids, were observed in the hard superficial knobs. These spicules are 9-14 /j. thick, and have terminal tyles about 30 m in diameter, beset with short anchor-teeth. I consider these spicules as foreign. The dermal 'pinules (Plate 54, figs. 35, 38-40) are generally pentactine, very rarely hexactine. The distal ray is 110-130 m long, and 4.5-9 /x thick at the base. It is straight, thickened above only very slightly or not at all, and ends with a slender and sharp-pointed terminal cone, only about 4 /j thick at the base, that is at the point of insertion of the uppermost spines. The basal part and the terminal cone of the distal ray are smooth, its middle-part bears sparse spines. The lowest spines are short, arise steeply, and are usually slightly inclined towards the tip of the ray. Sometimes they are more strongly inclined in this direction, sometimes vertical, and sometimes even inclined towards the base. Distally the spines at first increase in size, and then again become smaller. HYALONEMA (HYALONEMA) POLYCAULUM. 203 Their inclination towards the tip generally increases uniformly towards the end of the ray. The individual spines are conic, pointed, and curved more or less, generally concave towards the tip (Plate 54, figs. 35, 40), sometimes in the opposite direction (Plate 54, fig. 38, the lowest) and occasionally in an S-shaped manner (Plate 54, fig. 39). The largest spines are 15-24 p long and 2.5-4 p thick at the base. The maximum thickness of the distal ray, together with the spines, is 24-40 p. The lateral rays are blunt-pointed or terminally rounded and 24-40 p long. They bear rather sparse, conspicuous spines. The proximal ray does not, when present, exceed the lateral rays in length. The gastral pinules (Plate 54, figs. 41-45) are also usually pentactine; hexac- tine forms are, however, not so rare among them as among the dermal pinules. The distal ray is 110-133 p long and 6-9 p thick at the base. It is straight, simply conic throughout, or cylindrical basally and conic distally, or very slightly thickened below the middle of its length. It ends with a slender and very sharp- pointed terminal cone, 20-35 p long, and 3-5 p thick at the base, that is at the point of insertion of the uppermost spine. Nearly the whole of the distal ray, with the exception of the terminal cone, is spined; a spineless basal region being absent altogether, or quite insignificant. The spines are sparse. The largest arise from the middle-part of the ray. From here they decrease in size both dis- tally and proximally. The basal spines are vertical or slightly inclined, either towards the tip or the base of the ray. Distally they become more and more inclined towards the tip of the ray. The individual spines are conic, sharp- pointed, straight or slightly curved, either uniformly concave towards the tip of the ray, or, more rarely, uniformly concave in the opposite direction, or in an S-shaped manner. The largest spines are 12-16 p long and 3-4 p thick at the base. The maximum thickness of the distal ray, together with the spines, is 25-40 p. The lateral rays are 40-60 p long, usually conic, sharp-pointed, and in their distal two thirds or to a farther extent, often quite down to their base, they are covered with somewhat sparse, conspicuous spines. The proximal ray is, when present, similar to the lateral rays in shape and spinulation and has a maximum length of 50 p. The pinule-like pentactines, which may be canalaria (Plate 54, figs. 34, 37), have straight, conic, sharp-pointed rays, rather densely covered throughout with small spines. Their apical ray is 110-135 p long, their lateral rays about 65 p. The rays are 5-6 p thick at the base. The (hypodermal and ? hypogastral) pentactine- megascleres have fairly straight rays. The rays of the smaller forms are conic, very blunt-pointed, 204 HYALONEMA (HYALONEMA) POLYCAULUM. smooth in their basal and spined in their distal part. Those of the large forms are often nearly cylindrical, rounded at the end, and entirely destitute of spines. In the smaller forms the apical (proximal) ray is usually about 300 /z long, the longest lateral ray being 220-340 id. In the large forms the longest lateral ray attains a length of 650-1050 The basal thickness of the rays is 20-32 n in the former, and 40-80 i± in the latter. The hexactine megascleres (Plate 53, fig. 8) have conic and blunt, usually fairly straight rays. In many, two opposite rays are longer than the other four. The intact hexactines observed were 0.6-1. 6 mm. in maximum diameter, and had rays 15-35 n thick at the base. Some fragmentary ones had rays as much as 40 /d thick. Among the stout-rayed tetractine and tetractine-derivate acanthophores (Plate 54, figs. 1-15), which form the principal part of the skeleton of the hard superficial knobs, forms occur with four, three, two, and one ray. Those with four rays, that is the tetractines (or stauractines), are the most frequent. The rays of these spicules are on the whole cylindrical or cylindroconic, and rounded or, more rarely, abruptly pointed at the end. They are straight or slightly curved, and generally somewhat irregular in outline. The end-part of the ray is always densely spined, the proximal part, usually one half to two thirds of it, is smooth. Sometimes the spines extend farther proximally, occasionally quite down to the centre of the spicule. The tetractines (stauractines) and triactines (tauactines) (Plate 54, figs. 1-10) are 150-650 /d in diameter, and have rays 10-37 m thick at the base. The diact.ines (Plate 54, figs. 11, 12) are usually straight (Plate 54, fig. 12) or more rarely abruptly rectangularly bent at the morphological centre (Plate 54, fig. 11). The morphological centre is always thickened to a central tyle, which is generally smooth, or more rarely spined. These spicules are usually 0.4-1 mm. long, and 20-25 m thick near the middle. The central tyle measures 30-50 m in diameter. The monactines (Plate 54, figs. 13-15) are usu- ally 250-450 /d long, more or less cylindrical, 10-20 m thick, and closely resemble single rays of the other forms. The end corresponding to the morphological centre is thickened to a more or less spherical terminal tyle 18-40 /x in diameter. The slender -rayed, long-spined acantho'phores of the hard superficial knobs (Plate 54, figs. 30-33, 36) are usually hexactine, pentactine, or more rarely tetractine. The hexactines and pentactines form a series extending from regular hexactines (Plate 54, fig. 32) to pinule-like pentactines (Plates 54, fig. 35). The tetractines are to be considered as pentactine-derivates. These slender- rayed spicules measure 80-180 ^ in diameter. Their rays are straight, joined HYALONEMA (IIYALONEMA) POLYCAULUM. 205 at right angles, 3-8 n thick at the proximal end, conic, pointed, and covered with somewhat sparse spines cpiite or nearly down to the base. The largest spines are 5-15 n long and 2-3 n thick at the base. The basal spines arise vertically; the distal ones are inclined towards the tip of the ray. The microhexactines (Plate 53, figs. 9-12, 14-16) measure 80-142 /x in diam- eter, and have fairly equal, straight, or only very slightly curved, conic, and pointed rays, which are joined at right angles in the centre of the spicule. The rays are 2.5-4 m thick at the base and covered along their whole length with spines sometimes 0.4 n long. The basal spines are sparse and vertical, the distal more crowded and oblique, inclined backwards, towards the centre of the spicule. The rare microhexactine-derivates appear as spined amphioxes, from the centres of which arise terminally rounded rudiments of the four reduced rays. In respect to size and spinulation they agree with the largest regular micro- hexactines. The choanosomal rhabds are mostly centrotyle amphioxes, more rarely styles (tylostyles) . They are mostly 1-2 mm. long and 10-20 m thick. The central tyle is relatively much larger in the thin than in the stout amphioxes, and measures 15-35 m in transverse diameter. The proportion of the thickness of the parts of the spicule adjacent to the tyle and of the tyle itself is 100:110- 100:250. It is to be noted that the tyle, particularly in the slender rhabd, is often very eccentric, the four rays, the remnants of which it represents, being not all reduced to the same extent. The diactine ( diactine-derivate ) rhabd acanthophores of the hard superficial knobs (Plate 53, fig. 17 ; Plate 54, figs. 16-20) are simple or centrotyle cylindrical rods, often thickened, and usually densely spined, rarely smooth at the rounded or spindle-shaped ends. They are straight or irregularly, sometimes (Plate 53, fig. 17) very strongly curved. These spicules are usually 0.6-1. 4 mm. long and 4-20 n thick. The central tyle has a maximum in transverse diameter of 35 /x. The smooth, strongly curved form (Plate 53, fig. 17) is only 5.5 m thick, and about 180 m long measured along the curve. The upper ends of the stalk- spicules found in the parts of the body underlying the hard superficial knobs attain 15 ^ in length, and are 50-110 n thick at the lower, broken ends and attenuated above. In places these rods are irregular and knotty. Their axial threads at these points exhibit remarkable irregularities, from which I inferred that the spicules had here been broken and then again joined by freshly apposed silica-layers. Of amphidiscs three kinds (which correspond to the large macramphidiscs 206 HYALONEMA (HYALONEMA) POLYCAULUM. and the large and small micramphidiscs of Hyalonema (. Hyalonema ) obtusum ) can be distinguished : — macramphidiscs, large micramphidiscs, and small micramphidiscs. The macramphidiscs (Plate 53, figs. 1-3, 13; Plate 54, figs. 28, 29) are 200- 365 n long, most frequently about 293 //. The shaft is cylindrical, straight, 6.5- 12 n thick, and abruptly thickened in or near the middle to a central tyle 12-18 n in diameter. The proportion of the thickness of the adjacent parts of the shaft to the thickness of the tyle is 100 n to 115-170. A verticil of truncate or blunt-pointed, often irregularly curved spines 3.5-7 n long and 2.5-4 n thick arises from this tyle. Spines similar in shape but smaller (particularly shorter, only 1.5-3 n long and 2-3 ij thick) are scattered in larger or smaller numbers over the other parts of the shaft. The tips of the spines are smooth or slightly roughened. The terminal anchors are 60-100 n long, usually consid- erably less than a quarter of the whole spicule, and 67-107 n broad. The pro- portion of their length to their breadth is 100 to 103.8-125.7, on an average 100: 115.5. They consist of ten to twelve teeth. The individual teeth are curved in their (shorter) proximal part and generally nearly straight in their (longer) distal part. The latter usually diverges considerably and encloses an angle of about 20° with the shaft. The teeth are T-shaped in transverse section. Their upper part appears as a band about 10 /z broad and is abruptly attenuated to a point at the end. The large micramphidiscs (Plate 53, figs. 5, 6; Plate 54, figs. 26, 27) are 30-56 n long. The shaft is straight, 1.2-1. 7 n thick, and gradually thickened in a spindle-shaped manner in or near the middle. It bears a few small cylindri- cal spines. Some of these always arise from the central thickening. The anchors are usually 13.5-17 n long, generally considerably more than one third of the whole spicule, and 8-10 n broad. The distal parts of the individual teeth are fairly straight and generally nearly parallel to the shaft. The small micramphidiscs (Plate 53, fig. 7 ; Plate 54, figs. 21-25) are 13-27 n long, most frequently about 19.5 n. The shaft is straight, cylindrical, and 0.7-1. 5 n thick. Its central part usually bears a few spines. The anchors are 4. 5- 7. 5 m long, usually a quarter to a third of the whole spicule, and 5-8 fx broad. The individual anchor-teeth, of which there are about eighteen in one anchor, are more strongly curved some distance from the base than elsewhere. The end-part is nearly straight, and diverges very slightly or not at all from the shaft. The spiculation of the four hard superficial knobs indicates that the sponge above described had at least two, probably four, distinct and distant stalks, each composed of a separate bundle of spicules. HYALONEMA (HYALONEMA) PLACUNA. 207 Authors attach considerable systematic importance to the structure of the organs of attachment in the hyalonematids, and have established genera (Phero- nema, Poliopogon) for sponges in which this attachment is effected by a broad spicule-brush or a number of separate spicule-bundles, and not, as in Lopho- physema, etc., and the species of the genus Hyalonema, by a simple slender stalk. Under these circumstances, and in view of the fact that the genus Hyalonema is characterized by the possession of a single slender stalk-spicule bundle, it at first sight seemed advisable to consider the sponge above described not as belong- ing to Hyalonema, and either to place it in one of the old polycaule genera (Pheronema or Poliopogon), or to establish a new genus for it. Since it has a rudiment at least of a gastral cone, which excludes it from Pheronema or Poliopogon; since it is very similar in habit and spiculation to the forms C, D, and E of Hyalonema ( Hyalonema ) agassizi; and since it seems to me very doubtful whether the difference between a monocaule and polycaule attachment is, by itself, sufficient for generic distinction, I place it in the subgenus Hyalo- nema. The nearest ally to it is H. (H.) agassizi. From this it differs by the large macramphidiscs, the pinnies, and the mode of attachment. The large macram- phidiscs are considerably longer, their anchors relatively much broader, and the distal parts of their anchor-teeth more straight and divergent in the sponge above described than in H. (II.) agassizi. The distal rays of the pinules of the former are more conic than those of the latter, and not distally thickened as in II . (H.) agassizi, the terminal cone consequently being much more slender than in H. (H.) agassizi. These pinule-rays differ also in respect to their spinulation, their spines being more numerous in H. (H.) agassizi than in II. (H.) polycaulum. H. (H.) agassizi has a single stalk, H. (H.) polycaulum has several. These, and other minor differences, render it advisable to separate these sponges specifically. Hyalonema (Hyalonema) placuna, sp. nov. Plate 63, figs. 29-51; Plate 64, figs. 1-19; Plate 65, figs. 1-23; Plate 66, figs. 1-5. Two specimens of this species were trawled in the Central Tropical Pacific at Station 3684 (A.A. 17) on 10 September, 1899; 0° 50' N., 137° 54' W.; depth 4504 m. (2463 f.) ; they grew on a bottom of light yellow-gray Globigerina ooze. In their outer appearance they to a certain extent resemble Placuna shells and to this resemblance the name refers. Although similar and doubtlessly referable to the same species, the two 208 HYALONEMA (HYALONEMA) PLACUNA. specimens differ in detail to such an extent that I have established two distinct forms, A and B. Shape and size. The specimen of form A is the better preserved. This sponge (Plate 64, fig. 11) appears as a thin, irregularly oval lamella with a slight marginal protuberance at one of the narrow ends. Part of its margin is torn off. The sponge is 65 mm. broad and, together with the protuberance, 80 mm. long. A number of transverse folds slightly protrude from its surface. These folds are strongly inclined towards what appears to be the upper end of the sponge, and are here more numerous and crowded than below. Their margins form more or less concentric curves, which are convex towards the upper end of the sponge and extend across the whole lamella. These folds, which are much more clearly marked on one face of the lamella than on the other, give to the sponge its Placuna-like appearance. The sponge is not, as at first sight appears, a simple plate, but is composed of two lamellae, 1.5-3 mm. thick, closely pressed together and joined along one side. In life it was probably a thin-walled sac, and I am inclined to ascribe its present lamellar shape to a compression and complete flattening after capture. The intact parts of the free margin of this sac bear a frill of freely projecting spicules. The protuberance (Plate 64, fig. 11) is part of this marginal frill. The outer surface appears rough and exhibits the folds mentioned above. Aper- tures (pores) were not found in it. The inner surface is smooth, and also bears a few strongly inclined projecting folds. The specimen of form B is similar (Plate 64, fig. 12), but more fragmentary. It appears as a lamella, about 3 mm. thick, with somewhat irregular outline, and is 65 mm. long and 42 mm. broad. The colour of both specimens in spirit is dirty white. Skeleton. The outer surface is covered with a dense fur of large dermal pinules (Plate 64, fig. 13a; Plate 65, figs. 22, 23). Diactine pinules and centro- tyle amphioxes protrude from the sharp margin of the probably sac-shaped body. These pinules form the marginal frill referred to. The inner surface like the outer bears pinules. These gastral pinules are smaller, scarcer, and not nearly so densely crowded as the dermal. In form B two kinds of internal pinules can be distinguished, a larger with long lateral rays, and a smaller with apparently rudimentary lateral rays. The former are certainly gastral, the latter may be canaliculate. Megascleres are very abundant just below the surface and in the interior rhabds. Most of them are centrotyle amphioxes of moderate thickness; some are short spindle-shaped centrotyle amphioxes with remarkably HYALONEMA (HYALONEMA) PLACUNA. 209 large tyle ; a few are diactine centrotyle styles and tylostyles. Hypodermal and hypogastral pentactines occur below the outer and inner surface, and hexactine megascleres in the interior. Numerous microhexactines and a few diactine microhexactine-derivates are found in all parts of the sponge. Seven forms of amphidiscs can be distinguished : — 1 , large macramphidiscs with apically broad anchors; 2, small macramphidiscs with apically narrow anchors; 3, large, 4, medium, and 5, small mesamphidiscs; 6, large micramphidiscs with narrow anchors; and 7, small micramphidiscs with broad anchors. In form B all the seven kinds of amphidiscs occur. In form A No. 1 (the large macramphidiscs) and No. 3 (the large mesamphidiscs) are very rare, and No. 5 (the small mesam- phidiscs) are apparently altogether absent. In form B I found a tetraclisc. The dermal pinnies (Plate 64, figs. 8-10, 13a, 14-19; Plate 65, figs. 22, 23) are nearly always pentactine, very rarely hexactine, and have a large, bushy distal ray and short lateral rays. Those observed of form A (Plate 64, figs. 8, 14-1G) were all pentactine. They have a straight distal ray, 414-475 /x long, most frequently about 425-440 fx, and 7.5-10.5 /x thick at the base. This ray ends with a stout terminal cone protruding about 20 /j. beyond the tips of the uppermost spines. Apart from this terminal cone and the basal end-part., the whole of the distal ray is covered with spines. The lowest spines are strongly divergent and rather far apart. Distally the spines become more and more inclined towards the tip of the ray, and much more crowded. The uppermost spines are nearly parallel to the axis of the distal ray. The lowest spines are quite short. Distally they increase in dimension, and attain their maximum size at from two thirds to three quarters of the length of the distal ray from the centre of the spicule. Beyond this point they again become smaller. The largest spines are about 40 /x long and 2-3 n thick at the base. It seems that the basal parts of these spines are somewhat flattened, their diameter in a direc- tion radial to the distal ray being smaller than their diameter in a direction verti- cal to this. These distal pinule-rays have the appearance of wheat-ears; this is due to a slight, just perceptible curvature of the spines towards the tip of the ray, to the increase in their size towards a point in the distal half of the ray, and to their density. The maximum thickness of the distal ray, together with the spines, is 32-50 m, most frequently 38-47 n. This maximum thickness lies near the distal end of the ray. The proportion of the total length of the distal ray to the distance between the point of its maximum thickness, together with the spines, and the centre of the spicule (the base end of the distal ray) is 100 to 65.1-83.3, most frequently 100 to 70-78, on an average 100 :73.8. 210 HYALONEMA (HYALONEMA) PLACUNA. The lateral rays of the same spicule are usually all alike. They are 25-42 n long, attenuated distally, in their basal part very gradually, in their distal part abruptly, and pointed at the end. Sometimes one (Plate 64, fig. 8, to the left) or more (Plate 64, fig. 8, to the right) of them are reduced in length, only 20-24 n long, nearly cylindrical, and rounded at the end. The lateral rays are smooth, or provided with a few small spines. The dermal pinules of form B (Plate 64, figs. 9, 10, 17- 19) differ from those of form A chiefly in the maximum thickness of their distal ray, together with the spines, which is situated farther up, nearer to the tip of the ray. These pinules are not, as those of form A appear to be, all pentactine, but some hexactines occur among them. The distal ray of these spicules is 385-458 m long, most frequently 399-445 and 7-11 m thick at the base. The terminal cone is usually 18-27 n long. The maximum thickness of the distal ray, together with the spines, is 35-62 m, most frequently 40-60 /j. The proportion of the length of the distal ray to the distance between the point of maximum thickness (together with the spines) and the centre of the spicule (the base of the distal ray) is 100 to 71-86, most frequently 100 to 76-84, on an average 100 : 79.6. The lateral rays are 28-44 ^ long. The proximal ray of one of the hexactine forms is 34 ^ long. The ordinary gastral pinules of form A are nearly always pentactine, very rarely hexactine. In form B pentactine forms only were observed. The distal ray of the ordinary gastral pinules of form A (Plate 65, figs. 19-21) is straight or, rarely, angularly bent and 153-390 m long, usually 200-360 n. It is somewhat spindle-shaped, thickest at a point about one third of its length from the base. At the base it measures 7-12 n, at the thickest point 10-16 m, in thickness, and it ends in a rather long and slender terminal cone. Its distal and its proximal end- parts are spineless. The remainder of it bears rather sparse and distant spines. The lower spines arise steeply or vertically from the ray and then curve upwards, often very markedly, towards its tip (Plate 65, fig. 21). The upper spines for their whole length are strongly inclined and slightly curved towards the tip of the ray. They decrease in size distally, the uppermost ones being very small. The maxi- mum thickness of the distal ray, together with the spines, is usually 30-38 u, rarely less, down to 22 The lateral rays are 37-85 m long, usually 40-70 n, conic, and pointed. They are in the distal half, or two thirds of their length, beset with somewhat sparse, conspicuous, vertical or outwardly directed spines. A good many of the pentactine forms of these spicules possess a large spine oppo- site the distal ray. This spine may be a rudiment of the proximal ray. In the rare cases where the sixth (proximal) ray is properly developed, it attains a length of 27-73 M. HYALONEMA (HYALONEMA) PLACUNA. 211 The ordinary gastral pinules of form B (Plate 65, figs. 16-18) are similar. All those observed were pentactine. Their distal ray is 164-286 m long, rarely 330 n, 8-11.5 n thick at the base, and at the point of maximum thickness li- ly.5 m thick. Everywhere, except at the base and at the tip, it bears spines, which are larger (17-25 n long) and, particularly the upper, more divergent than in form A. In many of these spicules the lower spines are irregular and branched (Plate 65, fig. 17). The maximum thickness of the distal ray, together with the spines, is 28-52 /x. The lateral rays are conic, pointed or blunt, 40-73 pi long, and either quite smooth or provided with a few very minute spines. Besides the pinules described above, other much smaller pinules with appar- ently rudimentary lateral rays (Plate 65, figs. 9-12) have been found in the spicule- preparations of the interior of form B. As I have not seen them in situ in the sections, I cannot say with certainty whether they are gastral or canalar. The probability is that they are canalar. These pinules are pentactine. Their distal ray is straight and 172-200 /x long, 7.5-9 pi thick at the base. It is some- what spindle-shaped and measures in thickness 11-13 pi at the point of maximum thickness, which is about a third of the length of the distal ray distant from the base. The distal ray ends with a terminal cone. Everywhere, except at its base and at its tip, it bears large and sparse, more or less irregularly arranged spines. The lower spines arise steeply or vertically from the ray and are often branched; the upper are inclined towards the tip and simple; the latter decrease in size distally. The lateral rays appear as short stumps only 10-14 pi long. Sometimes it seemed to me that their shortness was due to their being broken; in other cases they appeared to be quite intact. Occasionally one or a few large and slender spines arise from the lower side of the laterals. Sometimes a large spine of this kind projects downward from the centre of the spicule (Plate 65, fig. 11). Such a spine appears as a rudiment of a sixth proximal ray. The diactine marginal pinules. In the somewhat fragmentary specimen of form B the margin is torn off and these spicules are missing. In form A they are abundant. In this form they are slightly curved or nearly straight, and 0.9- 1.5 mm. long. The distal ray may be longer or shorter than the proximal. The former measures 520-700 fx in length, the latter 360-760 pi. At their base both rays are 9-1 1 pi thick. The centrum is thickened to a tyle 1 1-20 n in trans- verse diameter. The distal part of the distal ray bears spines strongly inclined towards the tip. This spiny part, which is usually 350-400 pi long, has, together with the spines, a maximum diameter of 26-30 pi. Of rliabds three kinds can be distinguished: — ordinary, isoactine, and centro- tyle amphioxes; anisoact.ine centrotyle rhabds with one longer and pointed and 212 HYALONEMA (HYALONEMA) PLACUNA. one shorter and terminally rounded and usually thickened ray; and short and stout cent.rotyle amphioxes. The ordinary centrotyle amyliioxes (Plate 63, fig. 46) are in both forms usu- ally 0.8-2 n long and 9-21 n thick near the centre. The central tyle is 14-22.5 n in diameter. The ends are blunt and usually irregular, with widened axial thread-ends. In these spicules the proportion of thickness (close to the tyle) to length is 1 : 50-72, on an average 1 : 63.3. The anisoactine centrotyle rhabds appear as centrotyle tylostyles or, more rarely, styles. They are shorter than the isoactines, and 11-23 n thick near the terminal tyle (rounded end). The terminal tyle is often irregular, and measures in transverse diameter 13.5-37 n, sometimes 14 n more than the adjacent part of the spicule. The short and stout centrotyle amphioxes (Plate 63, fig. 47) are 0.6-1. 6 mm. long, and 13-38 /u thick near the middle. The central tyle is 23-45 u in diameter. The proportion of the thickness (close to the tyle) to the length is 1 : 37-52, on an average 1:44. The hypodermal pentactines (Plate 63, figs. 48-50) appear to be about the same in both forms. It is to be noted, however, that forms with lateral rays over 480 fi in length were found only in form A. The proximal ray is usually slightly curved, conic, blunt, 470-800 n long, and 9-55 u thick at the base. The lateral rays may be fairly equal, or unequal in size. Sometimes their inequality is very great (Plate 63, fig. 48), the longest being nearly twice as long as the shortest. They are conic, very blunt, straight, or curved concave to the proximal ray, and usually also inclined in this direction. The longest lateral ray of the spicule is 220 ju-1.1 mm. long. Hypogastral pentactines were found only in the preparations of form B, and here also they are very scarce. Those observed had lateral rays 360-670 m long and 18-35 n thick at the base. The hexactine megascleres are scarce, but have been found in both forms. In both they measure 0.8-1. 2 mm. in diameter and have blunt conic rays 16-34 u thick at the base. The microhexactines and microhexactine-derivates form a series beginning with spicules composed of six fairly equal rays and ending with centrotyle diac- t.ines from the central tyle of which arise one to four ray-rudiments. The most frequent are the intermediate forms, representing the middle-part of this series, with two opposite rays longer than the other four. The regular microhexactines in both forms (Plate 64, figs. 4, 6, 7; Plate 65, HYALONEMA (HYALONEMA) PLACUNA. 213 figs. 3-8) measure GO-140 p in diameter. Their rays are straight throughout or slightly bent in their middle-part, but never markedly curved in their end-part. They are 1.4-2. 9 p thick at the base, conic, sharp-pointed, and covered with minute and slender, backwardly directed spines, only 0.3 p long. In the middle- part of the ray these spines are much more numerous than in the basal and end- parts. The irregular microhexactines have two opposite longer rays, and four shorter rays (Plate 64, figs. 2, 3, 5) vertical to the axis of the two longer. The two longer rays are usually fairly equal, the four shorter rays often very unequal. These spicules are in form A 120-195 p long and 90-130 p broad; in form B 110-170 m long and 80-135 p broad. Their rays are similar to the rays of the regular microhexactines above described, and are 1.8-2. 5 p thick at the base. Transitional forms connect these spicules on the one hand with the regular micro- hexactines and on the other with the diactine microhexactine-derivates. The diactine microhexactine-derivates (Plate 64, fig. 1) are 220-330 p long. Their central tyle measures 4-5 p in diameter. Their two properly developed rays are similar to those of the microhexactines and are 2.5-3 p thick at the base. The four other rays are reduced, often to quite insignificant protuberances of the central tyle. The degree of reduction of these four rays is, in the same spicule, usually different, some being generally 5-10 p and more long, while others are represented only by slight protuberances of the central tyle. The regular microhexactines are 60-140 p long, the ordinary irregular micro- hexactines 110-195 p long, a transitional form with reduced rays 13-25 long is 225 p long, one 10-22 long is 270 p long, and one 2-5 long is 330 p long. A comparison of these dimensions shows that the total length of these spicules, that is to say the length of their two properly developed rays, is in proportion to the degree of reduction of their four other rays. This correlation is obviously comparable to that found by me 1 in the microscleres of the Tetraxonia, where the number of rays is usually in inverse proportion to their size. I am inclined to ascribe this in the case of Hyalonema (. Hyalonema ) placuna to the same cause as in the case of the tetractinellids. I believe that the cells or assemblages of cells building spicules like the asters of the tetractinellids and the microhexactines and microhexactine-derivates here under discussion contain a certain and definite amount of potential energy available for spicule-building and that this definite amount of energy is expended by the spicule-builders in H. (H.) placuna either in producing six smaller more or 1 R. v. Lendenfeld. Die Tetraxonia. Ergeb. Deutsch. tiefsee-exped., 1907, 11, p. 64. 214 HYALONEMA (HYALONEMA) PLACUNA. less equal, or two larger and four more or less rudimentary rays. If this assump- tion is correct, and if the energy saved in the building of the smaller rays is utilised in increasing the size of the larger, the latter must be hypertrophic to a degree in proportion to the degree of reduction of the former as, in fact, they are. The arnphidiscs. As these spicules are more numerous in form B than in form A, I shall commence the description of them with an examination of the arnphidiscs of the former. The arnphidiscs of form B are 18.5-3b7 ^ long. The frequency of those of different length is shown in Figure 9. Macramphidiscs Micramphidiscs w anchors d anchors inoHcoiflOHOo^fflcow^cBaoooNNffln^iON i N®Hrilriodd^N-ilOoi^6CON(DN- 197 214-286 105-186 124-187 55-100 most frequently about /j 249 143 163 Thickness of shaft p 5 4-7 2-4 2-4 1-2 Diameter of central tyle p 7 6-11 2. 8-6. 5 3.5-6 1.4-3. 5 Length of terminal anchors limits n 73 71-130 38-72 40-82 17-42 most frequently about p 108 51 63 Maximum breadth of terminal anchors limits p 54 47-85 19.5-52 23-52 10-24 most frequently about p 65 31 44 Proportion of length to maximum breadth of terminal anchors 100 to limits 73 55-66 43-66 43-66 42-59 average 58.9 57 54.7 52.7 whole spicule, and 6-11 p broad. The proportion of their length to their breadth is 100 to 50-56, on an average 100 : 52.3. The individual teeth arise vertically from the shaft, and are strongly bent in their proximal, and fairly straight in their distal part. Their straight end-parts are usually parallel to the shaft. In form A these spicules (Plate 63, fig. 42) are similar in shape, but smaller and provided with somewhat narrower anchors. Their dimensions are here the following: — total length 28-38 p; length of terminal anchors 12-15 n; breadth of terminal anchors 6-6.5 p; proportion of anchor-length to anchor- breadth 100 to 43-50, on an average 100 : 47.5. The small micramphidiscs with broad anchors are abundant. Those of form B (Plate 63, figs. 37-41; Plate 65, fig. 13) are 18.5-42 p long, most frequently 26-32 p. The shaft is straight, 0.6-1 p thick, and either simple and cylindrical throughout (Plate 65, fig. 13) or thickened somewhere near the middle to a central tyle 1-1.3 p in diameter. This tyle and the middle-part of the shaft usually bear some minute low and broad spines, either on all sides or on one side only. The anchors are 6-16 p long, a little less than a third to two fifths of Only one observed. 2 Apparently absent. 3 Only three observed. HYALONEMA (HYALONEMA) PLACUNA. 219 the whole spicule, and 5-11 m broad. The proportion of their length to their breadth is 100 : 58-92, on an average 100 : 73.8. The teeth arise nearly vertically from the shaft, and are strongly curved in their proximal part. Their distal part is straight, or only slightly curved, concave to the shaft. Their end-parts usually diverge slightly from the shaft, sometimes they are parallel to it. In form A these spicules (Plate 63, figs. 43-45; Plate 64, figs. 14, 15) are similar. Their dimensions are here: — total length 21-34.5 most frequently 25-33 tx) anchor-length 7-12.5 anchor-breadth 5-9 u', proportion of anchor- length to anchor-breadth 100 to 56-100, on an average 100 : 71.7. Tetradisc. In form B I found a tetractine (stauractine) spicule (Plate 63, fig. 51) with irregular terminal anchors on three of the rays. The fourth ray is broken off. The four main-rays of this spicule are densely spined, and the straight ends of the anchor-teeth, particularly of the longest, also bear conspicu- ous spines on their inner side. This spicule has a total diameter of 87 m- The anchors are about 35 m long and 36 m broad. The above description shows that these two sponges differ from each other in respect to the shape and size of several of their spicules, particularly their dermal and gastral pinules. These differences are cjuite constant and striking. I do not, however, consider these differences sufficient for specific or varietal dis- tinction. I therefore place the two sponges in the same species and distinguish for them, within this species, two forms. There can of course be no doubt about this species belonging to the Hexac- tinellida Amphidiscophora. It is more difficult to determine the genus, as the remarkable shape indicates a new generic character. Since, however, the specimens on which it is based are somewhat fragmentary, and since no trace of a stalk or other supporting apparatus is present, I refrain from doing so and place it provisionally in the genus Hyalonema, subgenus Hyalonema, some of the known species of which are quite similar in respect to spiculation. These sponges are distinguished by their shape and the dimensions of their spicules to such an extent that they can not be assigned to any of the described species. Their nearest allies are Hyalonema (H.) tenuifusum and H. (H.) tylo- stylum. From these they differ by the presence of protruding ridges (folds) which are absent in the two last named species; also by the dermal pinules being smaller and having much shorter lateral rays than in H. ( H .) tenuifusum (the dermal pinules are larger than those of II . ( H .) tylostylum ); by their gastral pinules having longer distal rays than in H. (H.) tenuifusum (the gastral pin- ules are larger than those of H. (H.) tylostylum) ; by the microhexactines being 220 IIYALONEMA (HYALONEMA) SP. covered with conspicuous recurved spines; by the micramphidisc being longer and having much larger anchors than in H. (H.) tenuifusum, and being shorter and having relatively much broader anchors than in II. ( H .) tylostylum, and by other characters. These facts together with the widely separated habitats (fully 50 equatorial degrees) are sufficient for specific separation. Hyalonema (Hyalonema) sp. from Station 4656. Plate 68, figs. 26-33; Plate 69, figs. 1-5. Part of a macerated specimen was trawled off northern Peru, Station 4656, on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.); the bottom was composed of fine, green mud mixed with gray ooze; the bot- tom-temperature was 35.2°. It is obviously the basal part of a Hyalonema but cannot be determined specifically. The specimen (Plate 68, fig. 26) is an elongate, irregularly oval lamella 60 mm. long, 22 mm. broad, and 8 mm. thick. A stalk 5 mm. thick and broken off short arises from one of the two narrow ends. The colour is brown. Amphiox megascleres, basal acanthophores, stalk-spicules, and microhexac- tines, which doubtlessly belong to the sponge, are found in large numbers in the spicule-preparations. Only a few hexactine and pentactine megascleres, pinules, and amphidiscs were seen. Some of these are probably proper to the sponge, others foreign, and it is impossible in every case to determine with certainty. The pinules which seem to be proper to the sponge are of two kinds, larger and smaller. Both are pentactine. The larger have a bushy distal ray 460-540 /x long and 8-10 n thick at the base. The distal ray, together with the spines, is 40-60 ix in transverse diameter at the point of maximum thickness, which lies high up. The lateral rays are 50-73 m long. The dimensions of the smaller pinules (Plate 69, figs. 1, 2) are: — distal ray, length 124-360 m, basal thickness 7-12 ix, maximum thickness, together with the spines, 15-43 m; lateral rays, length 27-50 /x. A pentactine observed has conical lateral rays 750 tx long and 35 ix thick at the base. The hexactines are 0.7-1. 5 mm. in maximum diameter. The rays are 16-28 ix thick at the base, and usually somewhat unequal in size in the same spicule. The aniphioxes are 1.3-2 mm. long and 10-17 /j. thick near the centre. Most of them are distinctly centrotyle. The central tyle is generally about 5 /i more in transverse diameter than the adjacent parts of the spicule. HYALONEMA (HYALONEMA) SP. 221 The basal acanthophores (Plate 68, figs. 27, 28, 31-33) have from two to six rays, the tetractine (stauractine) forms greatly predominating. The tri- to hexactines are 230-820 n long and have rays 11-33 n thick at the base. The diactines are 0.7-1.15 mm. long and 7-30 /x thick near the centre. Most of them, particularly the shorter ones, are distinctly centrotyle; their central tyle is 12-02 which is sometimes 40 n more than the adjacent parts of the spicule in transverse diameter. The ends of the rays are thickened and densely cov- ered with rather large spines. The remaining parts of the spicules are generally smooth. In some stout-rayed tetractines a few spines arise also from the basal parts of the rays (Plate 68, fig. 31), and some diactines have a very spiny central tyle (Plate 68, fig. 27). In the lower part of the body fragments of uncinate anchor-spicules have been observed. A spicule of this kind measured is 11 n thick just above the anchor. The anchor is 25 /x long and 18 /x broad. The anchor-teeth are rather numerous, irregular, strongly recurved, and very blunt. The microhexactines (Plate 68, figs. 29, 30) are mostly rather regular and measure 85-150 n in diameter. In some, two opposite rays are longer than the other four. Such microhexactines are sometimes 200 ^ long and 120 n broad. The rays are 1.5-2. 5 m thick at the base, and usually slightly curved a little beyond the middle of their length. This curvature is often unequal in different rays of the same spicule. Occasionally monactine microhexactine-derivates have been observed. A spicide of this kind measured appears as a tylostyle 120 /x in length and 1 n in thickness, with a terminal tyle 3.5 m in diameter. Those amphidiscs (Plate 69, figs. 3-5) which can, with some degree of probability, be assigned to the sponge, fall into five categories: — large and small macramphidiscs, large and small mesamphidiscs, and micramphidiscs. The dimensions of these five kinds of amphidiscs are tabulated below: — Length of Breadth of Thickness of Diameter of Total length anchor anchor shaft central tyle V Large macramphidiscs 2S0-316 76-120 90-104 9-12 1 3— IS Small macramphidiscs 220-225 77-80 60-70 8 10 Large mesamphidiscs 136-168 46-66 22-43 2-6 2-8 Small mesamphidiscs 45-69 23 15-18 1.5-2 Micramphidiscs 20-29 4-7 6-8 0.6-1 222 IIYALONEMA (HYALQNEMA) TENUIFUSUM. In respect to its large pinnies this sponge somewhat resembles Hyalonema ( Hyalonema ) placuna, in respect to its large amphidiscs Hyalonema ( Hyalonema ) polycaulum. Hyalonema (Hyalonema) tenuifusum, sp. nov. Plate 67, figs. 1-26; Plate 68, figs. 1-25. A larger (a), and several fragments of another, smaller ( b ) specimen of this sponge were trawled off the coast of northern Peru at Station 4656 on 13 No- vember, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.); it grew on a bottom of fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. The name refers to the minute, exceedingly slender, centrotyle amphioxes so abundant in these sponges. Shape and size. Specimen (a) (Plate 67, fig. 1) appears as a somewhat lacerated lamella, irregularly oval in outline, 84 mm. long, and 56 mm. broad. At one of its narrower ends a stalk, 3 mm. thick, arises from its margin. This stalk lies in the same plane as the lamellar body of the sponge. The latter is stoutest some 20 mm. above the point where the stalk arises from it, and is here 12 mm. thick. Upwards and sideways the lamella gradually thins out towards the margin. The fragments of specimen (6) are lacerated pieces of a lamella 1.5-3 mm. thick. The lamellar body is not simple and solid throughout, in either of the specimens, but is partly composed of two lamellae in contact with each other. The inner surfaces of these lamellae are obviously gastral surfaces and it is probable therefore that these sponges are in truth calyculate, and that their present shape is due merely to a collapse of the walls, caused by pressure exerted during or after capture. The colour in spirit is brown, rather dark in (a), pale in (6). The skeleton. Both the outer dermal and the inner gastral surfaces are covered by a dense pinule-fur. Smaller gastral pinnies have been found in the walls of some of the canals. Below the dermal and gastral surfaces masses of paratangential rhabds form a kind of felt. These rhabds are mostly centro- tyle amphioxes, but derivates of these spicules, with one actine reduced in length and often thickened and terminally rounded, also occur among them. This spicule-felt is pierced by the proximal rays of hypodermal and hypogastral pentactines. Similar amphioxes and amphiox-derivates and occasionally hex- actine megascleres were observed in the interior. The microscleres are regu- lar microhexactines, irregular microhexactines with two opposite rays much longer than the others, minute centrotyle amphioxes, minute tylostyles, large HYALONEMA (HYALONEMA) TENUIFUSUM. 223 macramphidiscs, small macramphidiscs, and micramphidiscs. The large macr- amphidiscs are rather rare, the minute tylostyles, which may be foreign, very scarce. All the other kinds of microscleres are abundant. At the point of emergence of the stalk, numerous monactine to hexactine, stout acanthophores, occur at the base of specimen (a). The stalk itself consists of a dozen stout, and a number of more slender spicules twisted in the usual way. The dermal pinules (Plate 68, figs. 18-21, 24, 25) are nearly always pentac- tine, very rarely hexactine. The distal ray is straight, 336-550 n long, genei’ally 430-530 n, and, at the base, 8-11 m thick, rarely as much as 13 n. Its proximal end is smooth ; for the rest of its length it is covered with upwardly directed spines which are sparse, stout, short, straight, or only slightly curved, and strongly divergent below, and which increase in density and length, and decrease in divergence and thickness above, up to a point a short distance below the tip of the ray. From this point onward to the end of the ray the spines again become smaller, less divergent, and more and more curved, concave to the ray, the distal parts of the uppermost spines being nearly parallel or even convergent. The maximum thickness of the distal ray, together with the spines, is 37-65 The point of maximum thickness lies high up. The proportion of the total length of the distal ray to the distance of the point of maximum thickness from the centre of the spicule (the proximal end of the distal ray) is, in the dermal pinules of specimen (a), 100 : 64 to 84, on an average 100 : 79, in the dermal pinules of ( b ) 100 : 67 to 84, on an average 100 : 75.2. When the point of maximum thick- ness is very high up, the distal ray, together with the spines, appears club-shaped. The lateral rays of the same spicule are usually fairly equal, straight, cylin- droconical in the basal and middle-parts, and abruptly pointed at the end. They are, in the dermal pinules of specimen (a) rather smooth, and 52-90 m long; in those of (6) spiny, and 40-75 m long. The rare hexactine dermal pinules are quite similar to the pentactine. Their proximal ray reaches 103 /t in length. In a good many pentactine pinules of specimen ( b ) a little cluster of spines, about 4 /x long, arises from the centre of the proximal face of the cross formed by the lateral rays. This central spine-cluster may be a remnant of a reduced proximal ray. The gastral pinules (Plate 68, figs. 2, 3) are, like the dermal, usually pentac- tine, rarely hexactine. The distal ray is 101-228 n long, and 4-10 ^ thick at the base. It bears sparse spines directed obliquely outward and upward. The spines are usually only slightly curved, concave to the ray. Occasionally, however, the lowest spines exhibit a strong curvature in this direction. The 224 HYALONEMA (HYALONEMA) TENUIFUSUM. largest spines are usually those arising some distance below the middle of the length of the ray. Proximally they become shorter but remain nearly as thick; clistally they become both shorter and more slender. The spines on the distal part of the ray are usually very small, often quite rudimentary. At the point of maximum thickness, which is generally situated below the middle of its length, the distal ray is, together with the spines, 10-46 m in transverse diameter. The gastral pinules of specimen (a) appear to have on the whole more slender distal rays than those of ( b ). The lateral rays are straight, cylinclroconical, and 39- 92 n long, most frequently 45-70 /u. They are spiny. In the gastral pinules of specimen (a) their spines are usually cpiite numerous and small, in those of ( b ) often sparse and very large, 2-4 n long. The proximal ray of the hexactine forms is similar to the laterals but shorter. The canalar 'pinules (Plate 68, fig. 4) are very variable in appearance and form a series one end of which is represented by pinules similar to the gastrals, the other by pentactines the apical ray of which is only slightly longer and bears only slightly larger spines than the laterals. The distal ray is 68-120 n long, and 3.5-7 m thick at the base. It bears a few obliquely ascending, nearly straight spines, which attain a considerable size in the larger pinules of this kind. At the point of maximum thickness, which usually lies at or below the middle of its length, the distal ray, together with the spines, is 8-28 n thick. The hypodermal and hypogastral pentactines have a straight proximal ray 0.5-1 mm. long, and 10-60 n thick at the base. The lateral rays are straight, usually inclined more or less towards the proximal ray, and 0.2-1. 1 mm. long. I have often noticed a great inequality in the length of the lateral rays. In some of these spicules the longest lateral is nearly twice as long as the shortest. The choanosomal hexactine megascleres are 0.5-1. 5 mm. in total diameter, and have conical rays 9-27 m thick at the base. Besides the more or less intact hexactines from which these measurements were taken, fragments of such spicules were observed which indicate that hexactine megascleres also occur of dimensions considerably exceeding those given above. The centrotyle amphiox megascleres are more or less curved, 0.9-3. 4 mm. long, usually 1-2.4 mm., and 7-13 m thick near the middle. The central tyle measures 16-26 n in diameter, and is 1.2-2.9 times as thick as the adjacent parts of the spicule. The thin amphioxes have a relatively larger central tyle than the stout ones. The style amphiox-derivates are as thick as the amphioxes, but shorter. In these spicules one of the two rays is properly developed, the other reduced HYALONEMA (HYALONEMA) TENUIFUSUM. 225 in length, rounded at the end, and thickened so as often to attain a transverse diameter nearly equal to that of the “central” tyle, which in these spicules is of course very eccentric. The spicules forming the stalk are, at the point where they arise from the sponge-body, sometimes 0.5 mm. thick. Fragments of rhabds 20-40 n thick found in spicule-preparations of the interior are probably parts of young stalk- spicules. All the stalk-spicules observed were smooth. The stout acanthophores (Plate 67, figs. 6, 7) have from one to six, most frequently from two to four rays. The rays usually taper distally, more rarely they are cylindrical. The end-part is densely covered with spines, generally somewhat thickened, and terminally rounded, or more rarely, pointed. The diactine forms are centrotyle. The three- to six-rayed forms are 335-580 n in diameter, and have rays 10-20 n thick. In the three-rayed forms all the rays lie in the same plane; two generally in a straight line, and the third at right angles to these. In the four-rayed forms the rays also lie in one plane, and the adjacent ones enclose angles of 90°. These spicules therefore appear as crosses (stauractines) . In the rare pentactine forms four rays extend in a plane, enclose angles of 90° with each other and appear as lateral rays, whilst the fifth is verti- cal to the plane of the four others and appears as an apical ray. The rare six- rayed forms are regular hexactines. In the diactine acanthophores the rays lie in a straight or slightly curved line. These spicules are 675 /x— 1.1 mm. long and 10-12 n thick. Their central tyle is 17-30 /x in transverse diameter. They are connected by transitional forms with the ordinary centrotyle amphiox megascleres. These transitional forms are about as thick as the true diactine acanthophores, but longer, reaching 2.6 mm. in length, and have smaller central tyles. The monactine forms are tylo- styles 0.8-1 mm. long and 10-13 /x thick. The terminal tyle is about 22 n in diameter. The regular microhexactines (Plate 67, figs. 10, 11) have six regularly dis- tributed, conical and sharp- pointed, straight or slightly curved rays. The curvature is, when present, usually greater in the proximal than in the distal part of the ray. The rays are nearly smooth, or slightly roughened by the presence of exceedingly minute spines, which appear to be directed backwards towards the centre of the spicule. In specimen (a) the regular microhexactines are 110-155 u in total diameter, and have rays 1.5-2 ^ thick at the base. In specimen ( b ) these spicules are somewhat smaller, 80-105 n in diameter, and have rays 1-2 n thick at the base. 226 HYALONEMA (HYALONEMA) TENUIFUSUM. In specimen (6) I found a microhexactine with a branch-ray on one of its rays. In the irregular microhexactines (Plate 67, fig. 8; Plate 68, figs. 7-9, 12-15) two opposite rays, lying in the same spicular axis, are long and well-developed, the other four variously reduced. The two long rays may be considered as apical, the other four as lateral rays. The two long apical rays are considerably longer than the rays of the regular microhexactines, so that the maximum diam- eter, that is the total length of these spicules, exceeds the diameter of the regular microhexactines. The apical rays are straight or only very slightly curved in their basal and middle-part, conical, pointed, smooth, or slightly roughened by very minute spines, and are 1-2.2 m thick at the base. The degree of reduction of the four lateral rays is equal or unequal, and is generally very considerable. They may all be present and equally long, or one, two, or three of them may be shorter or altogether absent. When one or more of these rays have dis- appeared altogether, the remaining lateral rays are usually very short. Spic- ules in which three of the lateral rays have disappeared altogether whilst the fourth is only slightly reduced in length (Plate 68, fig. 13) are very rare. It is to be noted that the reduced lateral rays are not only shorter, but often also thinner than the apical, the difference in the basal thickness of the apicals and laterals often amounting to 0.5 m- The irregular microhexactines in both specimens are 125-400 /j. long and 8-112 m broad. There is a very clearly pronounced correlation between the length of the apical rays (the total length of the spicule) and the degree of reduction of the lateral rays (the total breadth of the spicule) ; the longer the apicals and the whole spicule, the shorter are the laterals and the narrower is the whole spicule. The irregular microhexactines 125-170 long are 72-112 broad. “ “ 190-220 “ “ 33-85 “ “ 280-400 “ “ 8-14 Thus these irregular microhexactines form a series connecting the (shorter) regular microhexactines described above with the (longer) minute centrotyle amphioxes described below. The minute centrotyle amphioxes (Plate 67, fig. 12; Plate 68, figs. 16, 17) are more or less curved, the central part usually in one direction, the two end- parts in the opposite, so that these spicules generally look like bows. They are mostly 580-830 n long, and 1.5-2 n thick near the middle. The central tyle is oval and measures 3-5 u in transverse diameter. The two rays are conical and HYALONEMA (HYALONEMA) TENUIFUSUM. 227 sharp-pointed. The whole spicule is entirely smooth. The largest of these spicules are quite similar to, and only slightly shorter than, the smallest centro- tyle amphioxes above described as megascleres, and they might indeed be con- sidered as small forms of these spicules. There is, however, a very conspicuous gap which lies between 2 n and 7 n in the biometrical frequency-curve of the thickness of all these spicules taken together. This gap makes the distinc- tion easy between those 2 ^ thick and thinner, above described as minute centrotyle amphioxes, and those 7 /x thick and thicker, above described as cen- trotyle amphiox megascleres. The rare minute tylostyles, which are perhaps, foreign, are 140-200 /i long. The tyle is not situated quite at the end, is oval in shape, 5 m in diameter, and roughened by minute spines. The ray is 2-3 n thick at the base, smooth, coni- cal, pointed, and straight, or slightly curved. The amphidiscs measured are 20-340 n long. Their biological length frequency-curve is interrupted by a large gap between 34 and 77 n, and by minor gaps the most conspicuous of which lies in the curve of specimen (a) between 160 and 230 /x, and in the curve of ( b ) between 152 and 202 /x. The amphidiscs 20-34 /x in length form, morphologically, a fairly homogeneous group; they are to be considered as micramphidiscs. The amphidiscs 77-340 ^ in length are morphologically not homogeneous, the small ones having slender and long anchors, particularly in specimen id), whilst the anchors of the large ones are stout and short. Since, however, the broad and narrow anchored forms are morphologically, connected by very numerous transitional forms intermediate in size, I think it best to consider all the amphidiscs 77-340 ^ long as one group of macramphidiscs. The larger (on the whole broad anchored) and the smaller (on the whole narrow anchored) macramphidiscs are distinguished biometri- cally by the gap above referred to in their length frequency-curve (for specimen (a) between 160 and 230 /x, and for specimen (6) between 152 and 202 id). In accordance with this gap I distinguish two kinds of macramphidiscs, small macramphidiscs (in specimen (a) 129-160 ^ long, in (6) 77-152 /d) and large macramphidiscs (in specimen (a) 230-330 ^ long, in (6) 202-340 /d ). The large macramphidiscs (Plate 67, figs. 2-5, 15, 26; Plate 68, fig. 1) are 230-330 /d long in specimen (a). The shaft is straight and cylindrical, 5-11 n thick, apart from an abrupt thickening somewhere near the middle and a gradual thickening towards both ends. The central thickening (tyle) is 10-20 ^ in diameter, usually about twice as much as the shaft. It bears a verticil of fairly straight, truncate, cylindroconical spines which are vertical to the shaft or, 228 HYALONEMA (HYALONEMA) TENUIFUSUM. more rarely, slightly inclined, and measure 5-12 ^ long and 2-4 n thick. From the other parts of the shaft arise a greater or smaller number of low truncate or terminally rounded protuberances 1-2 ,u long and 2-3 fi thick. The terminal anchors are 66-110 about a third of the whole spicule, and 61-97 /j. broad. The proportion of their length to their breadth is 100 : 84 to 102, on an average 100 : 93.6. The anchors in the larger forms are relatively broader than in the smaller, the fraction ^en^if being, roughly speaking, in proportion to the length of the amphidisc. The anchor-teeth arise vertically from the shaft, and are curved concave towards it. This curvature decreases distally, and is on the whole such that the ends of the teeth converge more or less. When this conver- gence is great the anchor may be, at its end, as much as 10 ^ narrower than in its broadest part. The individual teeth are 10-15 m broad, and abruptly and not sharply pointed (Plate 67, figs. 3, 4; Plate 68, fig. 1). In specimen ( b ) the large macramphidiscs are similar but have narrower anchors. Their dimensions in this specimen are: — length 202-340 n; thickness of shaft 5-13 n; diameter of central tyle 8-22 n; length of anchors 46-114 breadth of anchors 43-98 n ; proportion of anchor-length to -breadth 100 : 65 to 98, on an average 100 : 80.8. The small macramphidiscs (Plate 67, figs. 13, 14, 22-25; Plate 68, figs. 22, 23) are in specimen (a) 129-160 n long, in (6) shorter, only 77-152 ^ long. The shaft is straight or, rarely, curved and 2-3 n thick. A cluster of irregularly dis- posed, more or less oblique, and often considerably curved, cylindrical, truncate spines with a maximum length of 3 n arises from a point in or near the middle of the shaft. At this point the shaft is usually, but by no means always, gradu- ally thickened to a tyle sometimes 6 n in diameter. The remaining parts of the shaft are quite densely covered with smaller spines, generally cylindroconical and truncate, which have a maximum length of 2.3 n and are 1 n thick. The terminal anchors are somewhat different in the two specimens. In (a) they are 36-54 fj. long, over one quarter to over two fifths of the whole spicule, and 22-30 m broad, the proportion of their length to their breadth being 100 to 48-64, on an average 100 : 58.5; in (6) they are 34-63 m long and 18-43 ^ broad, the propor- tion of their length to their breadth being 100 to 46-75, on an average 100 : 54. Relative to the length of the whole spicule these anchors in specimen (a) are considerably shorter than in ( b ). The proportion of the total length of the spicule to the anchor-length is in (a) 100 : 27 to 34, on an average 100 : 30.5; in (b) 100 : 34 to 44, on an average 100 : 38.8. The individual anchor-teeth are strongly curved, concave to the shaft at the base, and only slightly and rather HYALONEMA (HYALONEMA) TYLOSTYLUM. 229 uniformly curved in the same direction for the remainder of their length. The tips of the teeth are sometimes abruptly bent inward. Occasionally in their middle-part, particularly in the forms with curved shaft, the teeth are slightly curved outward. The micramphidiscs (Plate 67, figs. 16-21; Plate 68, figs. 5, 6) are in speci- men (a) 24-34 yu long, in (6) 20-32 p. The shaft is straight, cylindrical, and 0.8- 1 /j. thick. It bears a small number of irregularly scattered spines in its usually gradually thickened central part. The terminal anchors are in specimen (a) 5-8 m long, a quarter to a third of the whole spicule, and 5-9 m broad; in ( b ) 7-10 m long and 6.2-10 m broad. The proportion of anchor-length to anchor- breadth is 100 : 87 to 130, on an average 100 : 99.1. The nearest allies of these sponges are Hyalonema ( Hyalonema ) placuna and II . (H.) tylostylum. From H. (H.) placuna they differ: — by their external shape; by possessing abundant minute slender centrotyle amphioxes; by having dermal pillules with much longer lateral and somewhat longer distal rays; by the distal rays of their gastral pinules being shorter; by their amphidiscs having smaller anchors; by their microhexactines being much less spiny; and by other char- acters. From H. {H.) tylostylum they differ by the larger size of their pinules; by the possession of numerous minute, slender amphioxes and microhexactines with four reduced rays; by the absence of tylostyles; and by having consider- ably smaller macramphi discs. Hyalonema (Hyalonema) tylostylum, sp. nov. Plate 69, figs. 6-25; Plate 70, figs. 1-10. I establish this species for two specimens trawled off northern Peru at Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.) ; the bottom consisted of fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. Shape and size. Both specimens are compressed, lamellar, and broader at one end than at the other. The narrower end is rounded, the broader irregular and lacerated. A stalk about 2 mm. thick and broken off short arises from the middle of the convexity of the narrower, rounded end. One of the specimens (Plate 70, fig. 6) is 50 mm. long, 33 mm. broad, and 7 mm. in maximum thick- ness; the other measures 75 by 50 by 10 mm. In both specimens the upper part consists of two lamellae pressed together and joined laterally and below. This structure and the spiculation of the inner and outer surfaces of the lamellae 230 HYALONEMA (HYALONEMA) TYLOSTYLUM. indicate that these sponges were, in life, cup-shaped and that they have lost their upper marginal part and have been compressed to lamellar structures without open gastral cavities during or after capture. The colour in spirit is dull brown. The skeleto7i. The distal rays of the dermal pinules form a dense fur on the intact parts of the outer surface (Plate 70, figs. 3b, 8). Numerous amphidiscs, chiefly small macramphidiscs, occur in and just below the dermal membrane. The shafts of these spicules are situated radially. About one half of each of these amphidiscs with one anchor protrudes freely beyond the surface; the other half with the other anchor is imbedded in the sponge (Plate 70, fig. 3a). The lateral rays of hypodermal pentactines extend just below the layer occupied by the lateral rays of the pinules. Large macramphidiscs with the shaft parallel or oblique to the surface occur a little farther. Besides these and down the proxi- mal rays of the hypodermal pentactines, small hexactine megascleres also occur in this region. The skeleton of the inner gastral face of the lamellae (cup-wall) consists of gastral pinules and hypogastral pentactines. Tylostyles, hexactines, numerous microhexactines, a few micropentactines, and a good many amphi- discs, chiefly small macramphidiscs and micramphidiscs, are met with in the choanosome amphioxes. The dermal pinules (Plate 70, figs. 1, 2, 3b, 8) are pentactine and have a straight distal ray. One of the many observed was hexactine, and one other had an angularly bent distal ray. The distal ray is 340-379 n long, most fre- quently 342-368 ix, on an average 355 /x, and, at the base, 8-11 n thick, generally about 9 ix- Its basal end-part, for a distance of about 30 m, is smooth, thence onward the distal ray is spiny. The lowest spines are scarce, short, and very divergent. Distally, up to a point 100-120 ^ from the tip of the ray, the spines become more crowded, longer and more strongly inclined towards the ray. Farther on they again decrease in length and divergence, the uppermost being nearly parallel to the shaft. At the point of maximum thickness, which lies high up, the distal ray, together with the spines, is 31-47 ix in transverse diameter. The lateral rays are cylindrical, usually rounded at the end, spined, and 27-42 /x long, on an average 35 n. The single proximal ray observed was about as long as the laterals. All the gastral pinules (Plate 70, figs. 9, 10) observed were pentactine. Their distal ray is straight, 120-245 /x long, most frequently 150-190 /x, on an average 166 /x, and, at the base, 5-10 m thick, generally about 8 m- It is sharp- pointed and markedly thickened some distance below the middle of its length. HYALONEMA (HYALONEMA) TYLOSTYLUM. 231 It bears spines which are somewhat irregular, strongly divergent, often vertical below, and which increase in inclination towards the ray distally. The longest spines arise from the thickest part of the ray, a little below the middle of its length. The maximum thickness of the distal ray, together with the spines, is 23-33 ix. The lateral rays are conical, pointed or somewhat blunt, very spiny, and 45-68 m long. The (hypodermal and hypogastral) pentaclines (Plate 69, fig. 7) have a conical blunt proximal ray 0.5-0. 8 mm. long, and 15-40 m thick at the base. The lateral rays are straight, conical, blunt, usually 0.3-0. 5 mm. long, rarely up to 1.4 mm.; in the same spicule they are often unequal, and vertical to the proximal ray or inclined towards it. The angle between proximals and laterals is 80-90°. The hexactine megascleres (Plate 69, fig. 6) are 0.4-1. 3 mm. in diameter. Their rays are conical, straight, and frequently unequal. Occasionally one ray is reduced in length, cylindrical, and terminally rounded. The basal thickness of the rays is 13-37 ix. The amphioxes (Plate 69, figs. 11-13) are generally slightly and uniformly curved, 0.6-3. 4 mm. long, and 10-30 ^ thick near the middle. A central tyle can usually be made out, but it is quite insignificant, as it was not more than 3 ix thicker than the adjacent parts of the spicule in any of the amphioxes measured. The tylostyles (Plate 69, figs. 8-10) are nearly straight, and 0.8-3. 1 mm. long. The terminal tyle is 6-22 /x thicker than the adjacent parts of the spicule, and measures 16-52 [x in transverse diameter. It is usually spherical and quite smooth. Sometimes (Plate 69, fig. 10) a short oblique spine arises from it. The shaft ends in a blunt point. Close to the tyle it is 10-30 n thick. In the small (short) tylostyles it tapers gradually from the tyle to the opposite blunt- pointed end. In the medium tylostyles it is cylindrical, of nearly uniform thick- ness for the greater part of its length, and tapers towards the blunt-pointed end only in the ultimate third of its length. In the large tylostyles the shaft is spindle-shaped and sometimes 20 /x thicker in its middle-portion than just below the terminal tyle. The fragments of stalk-spicules observed are smooth and, at the point where they emerge from the sponge-body, have a maximum thickness of 0.5 mm. The microhexactines (Plate 70, figs. 4, 5a, 7) and their rare pentactine-deri- vates (Plate 70, fig. 5b) are quite regular, the rays of the same spicule being fairly equal in size. The total diameter of these spicules is 75-170 /x , generally 104-140 fx. In most of them all the six rays are nearly straight. In some, one 232 HYALONEMA (HYALONEMA) TYLQSTYLUM. ray or, rarely, several rays are markedly curved. In such rays the curvature is not confined to the end-part. The rays are conical, fine-pointed, distinctly spiny, and at the base 1.5-2. 7 p thick, usually about 2 p. The rare pentactine forms differ from the liexactine ones only by having five rays instead of six. The amphidiscs are 29-410 p long. Their length frequency-curve exhibits one great interruption between 49 and 116 p. The amphidiscs under 49 p in length (that is those between 29 and 49) have relatively shorter and broader anchors, the amphidiscs over 116 p in length (that is those between 116 and 410) have relatively longer and narrower anchors. Thus both from a morphological and a biometrical point of view, two kinds of amphidisc are to be distin- guished : — micramphidiscs 29-49 p long with broad anchors, and macramphi- discs 116-410 p long with slender anchors. The length frequency-curve of the macramphidiscs is somewhat irregular, and exhibits a broad depression at about 250 p. In the amphidiscs under 250 p in length the average proportion of anchor-length to anchor-breadth is 100 : 58.3, in those over 250 p in length this proportion is 100 : 73.7. The macramphidiscs can therefore be subdivided into two groups: — small macramphidiscs 116-250 p long with relatively more slender anchors, and large macramphidiscs 250-410 p long with relatively broader anchors. The length frequency-curve of the micramphidiscs is quite regular and has only one very pronounced summit. These spicules form a single, homogeneous group. The large viacr amphidiscs (Plate 69, figs. 14, 19, 24, 25) are 260-410 p, most frequently about 378 p long. The shaft is straight, for the greater part of its length cylindrical, and 6-12 p thick. It is slightly and gradually thickened towards its ends, and to a greater extent and much more abruptly thickened at or near the middle to a central tyle. The ends are 2-7 p thicker than the cylin- drical part of the shaft. The central tyle is 13-28 p in transverse diameter, that is, 6-18 p more than the adjacent parts of the shaft. It bears a verticil of spines which are cylindrical, or only very slightly distally attenuated, terminally simply rounded or more rarely truncate, and more or less, often very considerably, curved (Plate 69, figs. 14, 19, 24, 25). The curvature is generally simple and extends in a plane which passes through the axis of the shaft. Usually all the spines of the tyle are curved in the same direction (towards the same end of the spicule) (Plate 69, figs. 19, 24). Occasionally the majority of them are curved towards one end and a minority of one or two towards the opposite end (Plate 69, figs. 14, 25). Generally the spines are simple, exceptionally bifurcate (Plate 69, fig. 14, the left one). These spines are 7-17 p long and 3-6 p thick. The HYALONEMA (HYALONEMA) TYLOSTYLUM. 233 remaining parts of the shaft bear a larger or smaller number of similar but much shorter and nearly straight spines, which are 3-6 n long, exceptionally 12 n, and 3-5.5 \x thick. The terminal anchors are 95-148 n long, usually a little over a third of the whole spicule, and 60-114 n broad. The proportion of their length to their breadth is 100 to 57-89, on an average 100 : 73.7. Although both in the larger and the smaller of these spicules relatively broad and relatively slender anchors are met, yet the relative anchor-breadth is, on the whole, correlated to the length of the spicule, so that, roughly speaking, the smaller the amphidisc the more slender the anchors. In the largest large macramphidiscs, over 350 n in length, the proportion of anchor-length to anchor-breadth is 100 to 62-89, on an average 100 : 78; in the smaller large macramphidiscs, under 350 n in length, this proportion is 100 to 57-79, on an average 100 : 68.6. The anchor consists of eight teeth. The individual teeth arise vertically from the shaft, are considerably curved, concave to the shaft in their proximal part, and slightly and quite uniformly curved in the same direction in then- distal and middle-parts. The curvature is such that the end-parts of the teeth are parallel or slightly convergent. In the latter case the end of the anchor is of course narrower than a portion of its middle-part. The anchor-breadth measurements given above are always the maximum breadths. The anchor- end breadth may be 14 m less than the maximum breadth. The teeth have the usual T-shaped transverse section. The upper and outer part, which corre- sponds to the upper stroke of the T, is a thin band of a fairly uniform breadth of 13-18 jj., to within a short distance of the end. The end itself is abruptly and not sharply pointed. The lower and inner keel, which corresponds to the lower stroke of the T, is 13-16 /x high near the base of the tooth and becomes gradually narrower towards the tip. The small macramphidiscs (Plate 69, figs. 20-23) are similar to the large ones, but have relatively narrower anchors, less distinct central tyles, and more spines on the shaft. These spicules are 116-240 ^ long, most frequently 130- 220 ix. The shaft is 2.2-6 ix thick. The central tyle is 4-14 n in transverse diameter, that is 1.8-9 /x more than the adjacent parts of the shaft. It bears a verticil of nearly straight, or, more rarely, strongly curved spines, which are vertical or oblique to the axis of the shaft. These spines are generally cylindro- conical, blunt, and 3-5 /x long. The remaining parts of the shaft are covered with much smaller spines. These are the more numerous and the more slender the smaller the spicule. 234 HYALONEMA (HYALONEMA) TYLOSTYLUM. The terminal anchors are 34-85 n long, from less than a third to more than two fifths of the whole spicule, and 19-53 m broad. The proportion of their length to their breadth is 100 to 46-88, on an average 100 : 58.3. As in the large macramphidiscs, the relative breadth of the anchors is, roughly speaking, in proportion to the size of the spicule. In the smaller small macramphidiscs, under 170 n in length, the proportion of anchor-length to anchor-breadth is 100 to 46-62, on an average 100 : 55.8; in the larger, over 170 m in length, this proportion is 100 to 48-88, on an average 100 : 60.8. The individual teeth are curved strongly in their basal part. Distally the curvature decreases, and it is on the whole such that the end-parts of the teeth are usually slightly convergent. In one of the spicule-preparations I found an amphidisc with a supernu- merary anchor-crowned ray arising from the central tyle. The main shaft is 110 m long and 2 n thick. The central tyle is 4 fx in diameter. The main ter- minal anchors are 32 n long and 31 m broad. The supernumerary ray is 27 m long. Its terminal anchor is 18 m long and 28 n broad. The ends of adjacent teeth of different anchors lie in a straight line. The main shaft and the super- numerary ray are densely spined throughout. This spicule might be termed a triadisc. The ynicramphidiscs (Plate 69, figs. 15-18) are 29-49 m long, most fre- quently about 35 n long. The shaft is straight, 0. 7-1.1 n thick, and either uni- form in thickness, cylindrical throughout, or slightly and gradually thickened at or near the middle to a central tyle which is sometimes 1.3 m in diameter. The shaft is either quite smooth or it bears a larger or smaller number of minute spines. The anchors are 5-11 n long, a quarter to a fifth of the whole spicule, and 5-9 m broad. The proportion of their length to their breadth is 100 to 65- 150, on an average 100 : 88.9. The anchors of the largest micramphidiscs, that is those over 40 n in length, are, on the whole, more slender than those of the others. The proportion of anchor-length to anchor-breadth is in these large micramphidiscs 100 to 75-87, on an average 100 : 80.8. The individual anchor- teeth are curved so that their end-parts are either parallel or convergent. The nearest allies of the sponges above described are the species Hyalonema ( Hyalonema ) placuna and H. (II.) tenuifusum described in this Report. From these they differ by possessing tylostyle megascleres ; by being destitute of microhexactines with two longer opposite (apical) and four more or less reduced (lateral) rays; by the smaller size of the distal rays of their dermal pinules, and. by other characters. HYALONEMA (HYALONEMA) GRANDANCORA. 235 Hyalonema (Hyalonema) grandancora, sp. nov. Plate 78, figs. 16-45; Plate 79, figs. 1-26. One specimen of this species was trawled in the Southeastern Tropical Pacific at Station 4701 on 26 December, 1904; 19° 11.5' S., 102° 24' W. ; depth 4142 in. (2265 f.); the bottom was composed of dark brown chocolate clay; the bot- tom-temperature was 35.3°. It possesses very large macramphidiscs with broad anchors, and to these the. specific name refers. Shape and size (Plate 79, fig. 12). The body of the sponge is upright, slightly compressed laterally, somewhat plicated, and rounded below. It is 35 mm. high, 42 mm. broad, and 20 mm. thick. The upper part is much injured. In the fresh state its apical face was probably concave, with a broad gastral cone arising from its middle-part. Around the gastral cone, which is still present, wide canals, separated by radial lamellae, extend downwards into the interior. An eccentrically situated stalk, 1.4 mm. thick at its point of origin, arises from the lower rounded end of the body. This stalk is broken off below. The upper part, which is still present, is 160 mm. long, and slightly curved in an irregular manner. To the upper half of the stalk a colony of eleven polyps (Palythoa sp.) is attached. The polyps of this colony are strongly contracted and about 2 mm. high. They have an oval transverse section 4 mm. long and 3 broad, elongated in the direction of the stalk of the Hyalonema. Their stomatodeum is also oval in section and measures 1 by 1.5 mm. The individual polyps are 8-15 mm. apart (measured from centre to centre) and distributed all round the stalk in an irregularly spiral manner. The coenenchym forms a thin bark on the stalk of the Hyalonema. From this the individual polyps arise. The colour of the sponge-body and of the crust of the Palythoa in spirit is brown. The skeleton. A pinule-fur covers the surface of the body of the sponge. Radial pentactines occupy the subdermal and subgastral layers. Hexactine megascleres are abundant in the interior. Rhabd megascleres and micro- hexac tines occur in all parts of the body. In its lower part are met slender, entirely spined pinule-derivate, and mon- to pentactine, ordinary stout and slender acanthophores. The mon- to pentactines with proximally smooth rays are much more abundant than the entirely spined one§. The stalk consists at its origin of nine fairly stout spicules. Four kinds of amphidiscs, all with smooth teeth, can be distinguished : — large and small macramphidiscs, and 236 HYALONEMA (HYALONEMA) GRANDANCORA. large and small micramphidiscs. The large macramphi discs and the small micramphidiscs are abundant, the others rare. A few amphidiscs 170-230 n long, with serrated teeth, have also been found in the spicule-preparations. Since, however, these spicules are very rare and were not observed in the sections, I take them to be foreign. All parts of the individual polyps and the bark-like coenenchym of the Palythoa are protected by an armour which extends, in the inner dermal layer of the stomatodeum of the polyps, far down into their gast.ral cavities. This armour consists entirely of siliceous spicules identical with, or at least very similar to, the acanthophores of the sponge. In the Palythoa armour the acant.hophores with only terminally spined rays form a small minority, the majority being entirely spined (Plate 78, fig. 20). The dermal pinnies (Plate 78, figs. 41, 44, 45; Plate 79, fig. 20) of the upper and middle-parts of the outer surface are pentactine. The distal ray is 240-293 m long, and 7-10 n thick at the base. Its proximal and distal end-parts are smooth. The latter appears as a rather long and slender terminal cone. The remaining part of the ray bears spines of medium size which are generally slightly curved, and concave towards the shaft. The maximum thickness of the distal ray, together with the spines, is 17-26 i±. The lateral rays are 25-45 p. long, conical, and less rapidly attenuated towards the end in their proximal than in their distal part. They are smooth in their proximal part; their distal and middle-parts bear sparse, low, and broad spines. The dermal pinules on the basal part of the sponge are similar but have distal rays only 190-260 m long. The pinules in the walls of the large efferent canals (Plate 78, figs. 32, 43), which may be considered as gast.ral or canalar, are nearly all pentactines, only very few are hexactines. The distal ray is 250-395 n long, and 4-8 m thick at the base. Its basal part is smooth for a considerable length, and the ray-ends in a slender and sharp-pointed terminal cone. The spines on its middle-part are rather small; its maximum thickness, together with the spines, is 11-23 id. The lateral rays are conical, slightly spined, and 43-72 ^ long. One of the few hexactine pinules, which I measured, had a proximal ray 50 ^ long. The (hypodermal and hypogastral) pe?itactines have straight conical rays. The proximal ray is 0.4-0. 7 mm. long and 22-70 /x thick at the base. The lateral rays are straight* 0.2-1. 2 mm. long, and generally just perceptibly inclined towards the shaft, so that the inner contour of any two opposite rays lies in a straight line vertical to the axis of the shaft. HYALONEMA (HYALONEMA) GRANDANCORA. 237 The hexactines (Plate 79, figs. 13-19) are 0.4-3 mm. in diameter, and have nearly equal or somewhat unequal, conical and pointed, straight or slightly curved rays 10-80 n thick at the base. The rhabds are centrotyle, generally more or less curved, 0.8-1. 3 mm. long and 10-20 m thick. The central tyle is 1-3 n more in transverse diameter than the adjacent parts of the spicule. Among the acanthophores the diactines and tetractines are much more frequent than the others. In the entirely spined forms the rays are shorter and thicker than in the ones with rays spined only terminally. The dimensions of these spicules are the following : — with 1 or 2 rays; more or less rod-shaped with 3 more or less equally developed rays with 4 or 5 more or less equally developed rays Acanthophores total length M thickness of rays M total length M thickness of rays M total length A* thickness of rays with rays spined only at the end 154-1100 10-41 285-385 18-28 120-350 9-26 entirely spined 85-290 28-58 147 30 90-152 20-26 In the rod-shaped monactines and diactines which are only terminally spined an inverse proportion between length and thickness is clearly pronounced: — the spicules of this kind 154-400 p long are 26-41, on an average 29.7 n thick “ “ “ “ “ 401-550 M “ “ 19-26, “ “ “ 22.5 M “ “ “ “ “ “ 551-1100 n “ “ 10-23, “ “ “ 15.2 m “ The entirely spined spicules of this kind exhibit a similar relation between length and thickness : — those 85-120 m long are 35-58, on an average 43.3 n thick “ 121-290 M “ “ 28-31, “ “ “ 29 M “ The long and slender diactines which are only terminally spined have a central tyle 2-8 m more in transverse diameter than the adjacent parts of the spicule. In some of the shorter and stouter ones the tyle is relatively larger. The spines are broad and conical. In the entirely spined forms they are usu- ally about 7 m, very rarely as much as 10 n, long and broad; in those with rays only terminally spined they are smaller. Besides these spicules a few pinule-like, entirely spined pentactine and hexactine acanthophores with one differentiated ray were found in the basal part of the sponge. The dimensions of these spicules, which I consider as pinule- 238 HYALONEMA (HYALONEMA) GRANDANCORA. derivates, are: — -differentiated (distal) ray, 40-75 p long, at the base 6. 5-7.5 n thick, and in the middle (together with the spines) 6-8 n thick; lateral rays, 45-57 n long; proximal ray, when present, about 15 n long. The few spicules with only terminally spined rays found in the Palythoa armour appear to be quite identical with the corresponding spicules (acantho- phores) in the basal part of the sponge. The entirely spined spicules which form the bulk of the Palythoa armour (Plate 78, figs. 20-40) are mon- to tetractine. The triactine and tetractine entirely spined forms, which are not numerous, are 85-164 n in maximum diameter and have rays 20-47 p thick. The much more numerous entirely spined monactines and diactines are 90-193 p long, on an average 126.7 n, and 24-60 n thick, on an average 43.5 p. A correlation (inverse proportion) between their length and their thickness is not indicated. These spicules usually appear as stout, terminally rounded rods. They often have one or two protuberances which are considered as ray-rudiments. The shortest spicules, relatively, of this kind, with rays longitudinally most strongly reduced, are oval (Plate 78, figs. 23-26). The spines are conical and usually about 10 n long and broad. The average dimensions (length and thickness) of the monac- tine and diactine entirely spined acanthophores in the sponge are 122 and 38.6 n, in the Palythoa 126.7 and 43.5 ix. Thus we see that, although there is no great difference between the two, these spicules are somewhat larger, particularly in thickness, in Palythoa than in the sponge. A greater difference is found in the average size of their spines, which is considerably greater in the spicules of the Palythoa armour, than in the corresponding spicules in the sponge. Finally it must not be forgotten that the percentage of entirely spined acanthophores is much greater in the Palythoa armour than in the sponge. All this shows that the Palythoa does not indis- criminately gather and embody the basal spicules shed by the sponge, on the stalk of which it grows, but selects and retains only the stoutest and most spiny ones as material for building its armour. In connection with this I should like to point out that, in the literature on the armoured zoanthid colonies living as space-symbionts on the stalks of Hyalonemae, their armour is described as consisting of sand-grains only,1 or partly of sand-grains and partly of sponge-spicules and other material,2 or of sand-grains and various other material in their lower part, but chiefly of the 1 J. S. Bowerbank. On Hyalonema mirabile. Proc. Zool. soc. London, 1867, p. 21, 23. 2 R. Hertwig. Report on the Actiniaria. Supplement. Rept. Voy. Challenger, 1888, 26, p. 39. HYALONEMA (HYALONEMA) GRAND ANCORA. 239 spicules of the sponges to which they are attached in their upper parts which lie close to the sponge-body.1 In the Palythoae investing the stalks of Hyalonevia ( Hyalonema ) grandancora, on the other hand, the armour is composed entirely of spicules of the sponge on which they grow. In these cases therefore the sym- biosis appears to be considerably closer than in the Hyalonema symbiont zoan- thid above referred to, which were examined by Max Schultze, Bowerbank, and R. Hertwig. The stalk-spicules. The parts of the stalk-spicules present in the specimen appear as rhabds with various markings on the surface. Near the point where they arise from the sponge they are 280-400 p thick. The microhexactines (Plate 79, figs. 21-23) are 100-170 p in diameter, and have straight, conical, sharp-pointed rays, 3.5-4 p thick at the base. The rays bear spines. These are sparse, large, and situated vertically on their basal part ; distally they become inclined backwards, towards the centre of the spicule, where they are more numerous and smaller. The largest spines are 0.8-1 /z long and 0.5-0. 7 p thick. From a morphological point of view two kinds of amphidiscs can be dis- tinguished : — those with relatively broad and short anchors, and few or no spines outside the central tyle on the shaft; and those with more slender anchors and spiny shaft. The amphidiscs are 17-510 p long. Apart from the few amphidiscs with serrated teeth referred to above, which are to all appearance foreign, no amphidiscs over 80 and under 250 p in length were found. Thus there is, as the adjoined graph, based on 168 measurements, shows, a great gap in their length frequency-curve between 80-250 p. The amphidiscs over 250 p in length are those with the broad anchors and more smooth shaft; the amphidiscs under 80 p in length are those with the narrower anchors and spiny shaft. Thus the morphological distinction between these two kinds of amphidiscs coincides with the biometrical, and I accordingly divide the amphidiscs into two main groups : — macramphidiscs with broad anchors and more smooth shaft over 250 p in length, and micramphidiscs with narrower anchors and spiny shaft under 80 p in length. Of the eighty-five macramphidiscs measured one was only 250 p in length, the other eighty-four were 318-510 p. I am not quite sure whether the single macramphidisc only 250 p long is to be considered as a normal amphidisc proper to the sponge. Assuming this to be so, two morphologically similar kinds of macramphidiscs may be distinguished, a larger and a smaller, separated biomet- 1 Max Schultze. Die Hyalonemen, 1860, p. 29. 240 HYALONEMA (HYALONEMA) GRANDANCORA. 3 Z rt> C W 3 Cfl 3 c c r Fig. 10. — Amphidiscs. Micramphidiscs Macramphidiscs HYALONEMA (HYALONEMA) GRAND ANGORA. 241 rically by a distinct gap in the length frequency-curve. The large macramphi- discs form, as the graph shows, a biometrically perfectly homogeneous group. Also among the micramphidiscs two morphologically and biometrically distinct kinds can be distinguished: — a larger kind, over 37 n in length, with longer anchors and stout central tyle ; and a smaller kind, under 31 n in length, with shorter anchors and a relatively much smaller central tyle, or no central tyle at all. The part of the length frequency-curve pertaining to the first, larger kind of micramphidiscs shows several ups and downs, so that this group cannot be considered biometrically homogeneous. However, in view of the morphological similarity of these larger micramphidiscs of various size, I do not think the depressions in this part of the curve (none of which extends down to the base (0) line) sufficient for a division of them into secondary groups. The second, smaller kind of micramphidiscs forms a biometrically homogeneous group. I distinguish accordingly four kinds of amphidiscs in this sponge: — large macramphidiscs, small macramphidiscs, large micramphidiscs, and small micr- amphidiscs. The large macramphidiscs (Plate 78, figs. 16-19; Plate 79, figs. 1, 2, 26) are 318-510 /x long, most frequently about 415 m- The shaft is generally straight, very rarely bent, cylindrical, 20-26 /x thick, and thickened gradually towards the ends, and abruptly in or near the middle to a central tyle 24-30 /x in trans- verse diameter, that is 3-7 ^ more than the adjacent parts of the shaft. The central tyle bears a verticil of truncate conical spines. These spines are usually fairly equal, 10-20 m long and 10-12 m thick at the base. Sometimes one or two are large and the others more or less rudimentary. The remaining parts of the shaft are either quite smooth (Plate 79, fig. 2), or they bear only one or very few protuberances, about as broad as the spines of the central tyle, but generally much shorter. The terminal anchors are 83-125 /x long, a quarter to a sixth of the whole spicule, and 135-200 ^ broad. The proportion of anchor-length to anchor- breadth is 100 to 142-190, on an average 100 : 165.4. The anchor consists of eight teeth. The individual teeth arise vertically from the end of the shaft, and are curved more strongly in their proximal than in their distal half. The extreme tips of the teeth are sometimes slightly and abruptly bent inwards. The curvature of the teeth is, on the whole, such that their end-parts generally diverge slightly from the axis of the shaft. The dimensions of the single small macramphidisc observed are: — length 242 HYALONEMA (HYALONEMA) GRANDANCORA. 250 n] thickness of shaft 13 n; diameter of central tyle 15 n; spines of central tyle 7 m long and 6 u thick; anchors 74 n long and 110 n broad. The large micramphidiscs (Plate 79, figs. 24, 25) are 37-80 n long, most frequently about 43, 55, and 70 n } The shaft is straight, 2-3.5 n thick, and somewhat gradually thickened in or near the middle to a stout, often rather irregular, and not very clearly defined central tyle, 3-6 m in transverse diameter, that is 1.5-3. 5 n more than the adjacent parts of the shaft. The tyle and the remaining parts of the shaft are quite densely covered with small, slender spines. The spines on the tyle are scattered, not arranged in a verticil. The terminal anchors are 12-29 n long, usually a little more than a third of the whole spicule, and 10.5-26 n broad. The proportion of anchor-length to anchor-breadth is 100 to 75-100, on an average 100 : 86.3. The individual anchor-teeth are strongly curved in their proximal parts and only slightly curved or nearly straight in their distal and middle-parts. Their ends generally diverge rather considerably from the axis of the shaft. The small micramphidiscs (Plate 79, figs. 3-11) are 17-31 n long, most frequently about 23.3 n. The shaft is generally straight, rarely bent in the middle, is 1.3-1. 6 n thick, and in the larger forms often slightly and gradually thickened in or near the middle, in the smaller generally of uniform thickness throughout. The shaft is quite densely covered with small slender spines. The terminal anchors are 4-13 n long, a quarter to a third of the whole spicule, and 6-14 n broad. The proportion of anchor-length to anchor-breadth is 100 to 85-140, on an average 100 : 123. The anchor-teeth are curved more strongly in their basal than in their distal part. Their ends are parallel or nearly so. The species is very well characterized by the large size and the great relative breadth of the anchors of its macramphidiscs. The only species which has similar macramphidiscs and pinules is Hyalonema ( Prionema ) agujanum described in this Report. From this it is distinguished by the large and slender amphi- discs with serrated teeth which are exceedingly abundant in H. ( P .) agujanum and absent in H. ( H .) granclancora. 1 Their length frequency-curve has three distinct elevations corresponding to these sizes. HYALONEMA (HYALQNEMA) SP. 243 Hyalonema (Hyalonema) sp. from Station 3684 (A. A. 17). Plate SO, figs. 1-16. A small fragment about 10 mm. long with several stalk-spicules was col- lected in the Central Pacific, Station 3G84 (A. A. 17) on 10 September, 1899; 0° 50' N., 137° 54' W. ; depth 4504 m. (2463 f.) ; it grew on light yellow-gray Globigerina ooze. This fragment appears to have formed part of a species of Hyalonema not sufficiently well-preserved for specific determination. The spicules of this fragment are pentactine pillules with long distal ray, pentactine pinnies with short distal ray, diactine pinules; hexactine, pentactine, and diactine megascleres; acanthophores ; stalk-spicules; microhexactines ; macramphidiscs ; and micramphidiscs. The 'pentactine pinules with long distal ray (Plate 80, fig. 16). The distal ray in these spicules is 375-670 ^ long, and 5-8 ^ thick at the base. It tapers gradually towards the fine-pointed end, and bears very small and rather sparse strongly inclined spines. These decrease in size distally. The lateral rays are spiny and 60-80 m long. The pentactine pinules with short distal ray (Plate 80, fig. 14). In these spicules the distal ray is 170-260 n long, and 4-8 m thick at the base. It bears rather strongly inclined spines, which are larger than in the pentactine pinules with long distal ray. The maximum thickness of the distal ray, together with the spines, is usually 11-16 n. The lateral rays are spiny and 60-70 n long. The diactine pinules (Plate 80, fig. 15). The total length of these spicules is usually 0. 7-0.8 mm. The distal ray is 390-480 m long, 5-8 ^ thick at the base, and covered with small, strongly inclined spines. The lateral rays are reduced to smooth, cylindrical, terminally rounded protuberances, (measured from the axis of the spicule) 6-17 \i long. The proximal ray is 305-330 m long. The pentactine megascleres have a proximal ray 450-600 ^ long, and 10-35 m thick at the base. The lateral rays of the same spicule are more or less unequal. The length of the smallest is not infrequently only two thirds of that of the long- est, sometimes even less. The lateral rays are straight, conical, blunt, and 170- 560 m long. The hexactine megascleres are 0.7-1. 8 mm. in diameter, and have rays 20- 40 m thick at the base. The diactine megascleres are centrotyle. The diameter of the central tyle is sometimes as much as twice as great as the thickness of the adjacent parts of the spicule. 244 HYALONEMA (HYALONEMA) SP. The acanthophores (Plate 80, fig. 13) have one to four more or less fully developed rays. The tri- and tetractine forms are 170-370 /x in maximum diameter, and have rays 13-22 n thick at the base. The diactine forms are 400- 900 n long, and 7-10 ^ thick near the centre. Most of them are centrotyle. The central tyle is not infrequently more than three times as stout as the adjacent parts of the spicule. The single monactine form observed is 260 n long and 15 /x thick. The stalk-spicules (Plate 80, figs. 11, 12) bear spiral rows of proximally directed spines on parts of their surface and terminate in anchors. The shaft of the stalk-spicule represented (Plate 80, figs. 11, 12) is 39 p thick just above the anchor, which is 145 /x long and broad. The microhexactines (Plate 80, fig. 4) are 150-170 p in diameter, and have equal rays 3.5-4 n thick at the base. The rays are conical, fine-pointed, spined, and nearly straight in their proximal part, but rather strongly curved towards their ends. Of amphidiscs two kinds can be distinguished: — macramphidiscs and micramphidiscs. The macramphidiscs (Plate 80, figs. 1, 2, 5-10) are 380-570 /x long, most frequently about 470 and 530 /x. The shaft is straight, 20-25 m thick, and thickened in or near the middle, only very slightly, or not at all, to a tyle, which however is not clearly defined. This tyle may, when present, bear one or a few blunt insignificant spines. The rest of the shaft is generally quite smooth. The anchors are 120-228 n long, less than a third to nearly half of the whole spicule, and 215-263 p. broad. The proportion of their length to their breadth is 100 to 115-191, on an average 100 : 147.8. The curvature of the anchor-teeth decreases distally, and their end-parts generally diverge. The extreme tip of the teeth, in the long anchors, is sometimes (Plate 80, fig. 2) bent inwards. The teeth have smooth lateral margins, and are pointed at the end (Plate 80, fig. 10). The micramphidiscs (Plate 80, fig. 3) are 26-28 m long, and have terminal anchors 9-10 n long, about a third of the whole spicule, and 8.5-11 /x broad. The proportion of anchor-length to anchor-breadth is 100 to 85-115, on an average 100 : 102.5. Among the species of Amphidiscophora hitherto described, Hyalonema martahanense F. E. Schulze 1 appears to be the one most closely allied to the fragment described above. This fragment differs from H. martahanense by 1 F. E. Schulze. Hexactinelliden des Indischen Oceanes. III. Abh. Akad. Beilin, 1900, p. 12, t. 2. Indian Triaxonia, 1902, p. 21, pi. 18. HYALONEMA (LEPTONEMA) CAMPANULA. 245 having no smaller kind of macramphidiscs, no mesamphidiscs, and no spheres, and by the distal ray of its pinules being more slender, and its microhexactines much larger. Although these differences are very conspicuous and quite suffi- cient for specific distinction, there is a considerable degree of similarity between the two. LEPTONEMA, subgen. nov. Species of Hyalonema the amphidiscs of which have hyperbolic, hemispheri- cal, or bell-shaped terminal anchors about one fourth to one third of the whole spicule in length. Without amphidiscs of any other kind. The largest amphidiscs are slender and have a thin shaft. The collection contains one specimen of this subgenus. Hyalonema (Leptonema) campanula, sp. nov. Plate 81, figs. 1-26. A single specimen of this species was trawled in the Southern Tropical Pacific at Station 4721 on 15 January, 1905; 8° 7.5' S.; 104° 10.5' W.; depth 3811 m. (2084 f.); it grew on light brown Globigerina ooze. The terminal anchors of the macramphidiscs are slender and similar to the flowers of certain species of Campanula. To this the name refers. Shape and size. The specimen (Plate 81, fig. 15) is somewhat fragmentary. What there is of the body is an irregular mass, 18 mm. in diameter. It is drawn out to a conical protuberance in one place, and from this arises a curved stalk 70 mm. long and about 1 mm. thick. The colour of the body in spirit is brown. The skeleton consists of pentactine and diactine pinules, pentactine, hex- actine, and diactine megascleres, modified basal spicules, stalk-spicules, microhex- actines, and amphidiscs. The diactine pinules are associated with ordinary diactine megascleres. Protruding freely they probably formed together with these spicules a fringe at the boundary between the dermal and gastral parts of the surface. Some of the pentactine pinules have a very long distal ray; in others, which appear to be confined to the basal part of the sponge, the distal ray is of ordinary length. The acanthophores are for the most part diactine and pentactine. The amphidiscs are of three kinds, macramphidiscs, mesamphidiscs, and micramphidiscs. The macramphidiscs are very abundant, the other two rather rare. 246 HYALONEMA (LEPTONEMA) CAMPANULA. The pentadine pinnies with long distal ray (Plate 81, figs. 12, 13, 16-18). In these spicules the distal ray is 230-810 n long, most frequently about 600 yu, 5-8 m thick at the base, and fairly straight or more or less, sometimes very con- siderably, curved. It is conical and it ends in an exceedingly fine, thread-like, spineless terminal cone. The spines of the distal ray are small, rather sparse, and strongly inclined towards the tip of the ray. They attain their largest size at a distance of a fifth to a quarter of the length of the whole ray from the centre of the spicule, and here the distal ray, together with the spines, attains its maxi- mum thickness of 9-18 m- The lateral rays are cylindroconical, abruptly pointed or blunt, and spiny in their distal part. Their length is, roughly speaking, in proportion to the length of the distal ray. In the pinules with a distal ray under 400 n in length, the lateral rays are 43-52 /x long; in those with a distal ray over- 400 yu in length, 50-S0 yu long. The basal dermal pentadine pinules with shorter distal ray (Plate 81, figs. 25, 26). In these spicules the distal ray is straight, conical, 100-165 ^ long, and 5-6 yu thick at the base. It bears rather sparse spines and ends in a sharp- pointed and rather slender terminal cone. Its maximum thickness, together with the spines, of 12^-23 m is usually situated a little above the middle of its length. The lateral rays are cylindroconical, abruptly pointed or rounded at the end, distally spined, and 37-58 m long. The diadine pinules (Plate 81, figs. 1, 2, 14). In these pinules the distal ray is straight or curved, 0.73-1.2 mm. long, and 6-9 m thick at the base. It bears rather sparse strongly inclined spines. The largest are 10-16 n long, and arise about a third of the length of the distal ray from the centrum of the spicule. Here the distal ray, together with the spines, attains its maximal thickness of 12-18 yu. Distally and proximally the spines decrease in size. The slender thread-like extreme tip and the basal part of the distal ray are free from spines. The proximal ray is usually fairly straight and 450-750 n long. The lateral rays are reduced to cylindrical, terminally rounded protuberances only 5-14 ^ long (measured from the axis of the spicule). The pentadine megascleres (Plate 81, figs. 19, 20) have a straight proximal ray sometimes 1 mm. and more long, and 7-45 n thick at the base. The lateral rays of the same spicule often differ very considerably in size. They are 230 ^ to 1 mm. long, straight, or somewhat curved, and slightly inclined towards the proximal ray; the angle between them and the proximal ray is usually about 85°. The lateral rays are generally conical and terminally rounded, rarely thickened at the end (Plate 81, fig. 19). HYALONEMA (LEPTONEMA) CAMPANULA. 247 The hexactine megascleres are 550 /*- 1.3 mm. in diameter. Their rays are 7-22 ix thick at the base, usually more or less curved, and only slightly attenuated toward the rounded end. The end-parts of the rays, particularly of the smaller hexactines, bear minute spines. The diactine megascleres are centrotyle amphioxes. They are usually 1-1.5 mm. long and 9-18 m thick near the centre. The central tyle is 12-22 n in transverse diameter, that is 2-4 ^ more than the adjacent parts of the spicule. The basal pentactine and diactine acanthophores are similar to the ordinary pentac tines and diactines of the body, above described, but have rays reduced in length and somewhat thickened and spined at the end. The stalk-spicules (Plate 81, fig. 11) have a maximum thickness of 1 10 m and all are broken off at the lower, distal end. Their proximal, upper parts are smooth. Farther down minute, strongly inclined, upwardly directed spines begin to make their appearance. Distally these spines become larger and appar- ently also less numerous. The spines are partly scattered, partly arranged in oblique (spiral) transverse rows. The microhexactines (Plate 81, figs. 3-6) are 50-100 m in diameter. The rays are 1-1.5 /x thick at the base, straight in their proximal, but curved in their distal part. This curvature is either fairly uniform or considerably greater just beyond the point where it begins than in the end-part, and on the whole such that the tips of adjacent rays come to be parallel or convergent. Morphologically two kinds of amphidiscs can be distinguished: — those with relatively thin shaft and slender, somewhat bell-flower shaped anchors; and those with relatively stout shaft and broader, oval anchors. The former are 150 ix or more long, whilst the largest of the latter is only 118 /x long. As the adjoined graph shows, a rather conspicuous depression in their length frequency- curve divides the large and slender-anchored amphidiscs biometrically into a larger and a smaller kind. In view of the morphological identity of the larger and smaller, I think that all these slender-anchored amphidiscs can be considered as amphidiscs of the same kind, and I shall describe them as macramphidiscs. The broad-anchored amphidiscs, 118 m or less in length, are divided bio- metrically by a very wide gap in the length frequency-curve, situated between 26 and 77 ix, into a larger and a smaller kind. The larger of these amphidiscs I shall describe as mesamphidiscs, the smaller as micramphidiscs. Since the length frequency-curve in both exhibits several depressions, neither of them can be said to form a biometrically homogeneous group. Since, however, those depressions are not very great and since these amphidiscs are so rare that 248 HYALONEMA (LEPTONEMA) CAMPANULA. Length, (/a). 15.86 — 17.45 — 19.19 — 21.11 — 23.23 — 25.55 — 28.10 — 30.91 — 34.00 — 37.40 — 41.14 — 45.26 — 49.78 — 54.76 — 60.24 — 66.26 — 72.89 — 80.18 — 88.20 — 97.02 — 106.72-4 106.72 — 117.39 117.39 — 129.13— 129.13 — 142.04- 142.04 — 156.25 156.25 — 171.87 171.87 — 189.06— 189.06 — 207.97- 207.97 — 228.76 228.76 — 251.64 251.64 — 276.81 276.81 — 304.49-4- 304.49 — 334.93 334.93 — 368.43 17.45- 19.19 21.11 23.23 25.55 H 28.10 30.91 34.00-^ 37.40 41.14- 45.26- 49.78- 54.76- 60.24 66.26- 72.89- 80.18- 88.20- 97.02 Fig. 1 1 . — Amphidiscs, Number HYALONEMA (LEPTONEMA) CAMPANULA. 249 I was unable to measure a number large enough to make the curves perfectly reliable, I shall not divide them into subgroups. The rnacramphidiscs (Plate 81, figs. 7-10) are 150-290 m long, most fre- quently about 250 /x. The shaft is straight or more or less, sometimes very considerably, curved, and 1.5-5 /x thick. It is thickened gradually towards the ends and more abruptly at or near the centre to a tyle 2.8-7 n in transverse diameter, that is 1-3 n more than the adjacent parts of the shaft. A few spines, 1-3 m long and 1-2 /x thick, forming a verticil arise from the central tyle. The remaining parts of the shaft are quite smooth or bear only one or a few small spines. The terminal anchors are 48-84 n long, about two sevenths of the whole spicule, and 25-53 m broad. The proportion of their length to their breadth is 100 to 46-69, on an average 100 : 57.8. The anchors are composed of eight teeth. The individual teeth are 9-12 n broad, hardly at all attenuated distally, and simply rounded at the end. They arise vertically from the shaft and are, at a distance of about one eighth of their length from the point of origin, abruptly and very strongly bent toward the shaft. The part beyond this bend, that is the distal seven eighths, is either quite straight or somewhat bent outward; rarely the end is slightly bent inwards. These long distal parts of the teeth are divergent and enclose angles of 9° or 10° with the axis of the shaft. The mesamphidiscs (Plate 81, figs. 23, 24) are 77-118 \x long, most frequently about 84 ix. The shaft is straight and 4-7.5 m thick. It thickens gradually towards the ends, which are usually 3-4.5 n thicker than the middle-part. There is either no central thickening at all, or it is quite insignificant, not exceeding the adjacent parts of the shaft by more than 1 ^ in thickness. The shaft bears a few terminally rounded spines 3-8 tx long and 2-5 /x thick, which do not form a central verticil, but are scattered irregularly over its middle-part. Sometimes only a single large spine arises from the shaft. The terminal anchors are 30-43 /x long, about a third of the whole spicule, and 40-47 /x broad. The proportion of their length to their breadth is 100 to 100-133, on an average 100 : 109. The anchor-teeth are in the medium-sized mesamphidiscs about 9 /x broad. They are attenuated distally, terminally rounded, and curved toward the shaft throughout their length. This curvature is much greater in their proximal than in their distal portion, and on the whole such that their end-parts diverge. The micramphidiscs (Plate 81, figs. 21, 22) are 18-26 /x long, most frequently about 24.5 /x. The shaft is straight and 0.9-1. 4 /x thick. A slight, not well- 250 PRIONEMA. defined central thickening can usually be made out. This is 1.2-1. 9 p in trans- verse diameter, that is 0.2-0. 5 \x more than the adjacent parts of the shaft. The anchors are 5-11 m long, one third to two fifths of the whole spicule, and 5.5-10 m broad. The proportion of their length to their breadth is 100 to 77-129, on an average 100 : 107. The curvature of the anchor- teeth decreases distally, and their end-parts are usually fairly straight. The total curvature is such that the end-parts of the teeth are either parallel or slightly divergent. Besides the amphicliscs above described, I found an abnormal amphidisc with very unequal terminal anchors. This spicule is 42 p long and has a shaft 2 [x thick. One of its anchors measures 18 p in length and 13 p in breadth, the other is 8 p long and broad. One half of this spicule appears as a mesamphidisc, the other half as a micramphidisc. Of the species of Hyalonema hitherto described H. divergens F. E. Schulze 1 appears to be the one most closely allied to the sponge above described. From this it differs, however, to a considerable extent by the shape and dimensions of the spicules. The large macramphidiscs 500 p long with ovoid anchors, which are present in H. divergens , are absent in H. (H.) campanula. The macramphi- discs with campanulate anchors are small and have a strongly spined shaft and pointed anchor-teeth in H. divergens, and are twice as large and have, apart from the centrum, a nearly smooth shaft and terminally rounded anchor-teeth in H. ( H .) campanula. These and the other less conspicuous differences are, of course, cjuite sufficient for specific distinction. PRIONEMA, subgen. nov. Species of Hyalonema of which the amphidiscs of one kind have anchor-teeth with serrated margin. The collection contains twenty-one more or less complete specimens and one fragment of this subgenus. They belong to six species, all of which are new. F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 199, pi. 28, figs. 1-11. HYALONEMA (PRIONEMA) AGUJANUM. 251 Hyalonema (Prionema) agujanum, sp. nov. tenuis, var. nov. Form A. Plate 72, figs. 17-21, 23-25, 27; Plate 73, figs. 1-6; Plate 74, figs. 1-5, 8; Plate 75, figs. 1-13, 15, 17, 19-27, 29-37; Plate 76, figs. 1-7, 11, 12, 15-36. tenuis, var. nov. Form B. Plate 72, figs. 16, 22, 26; Plate 73, fig. 7; Plate 74, figs. 6, 7, 9; Plate 75, figs. 14, 16, 18, 28; Plate 76, figs. 8-10, 13, 14. lata, var. nov. Plate 77, figs. 1-10; Plate 78, figs. 1-15. I establish this species for five specimens collected off northern Peru, near Aguja Point, at Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.); they grew on fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. The specific name refers to the locality. I distinguish two varieties in this species, one comprising four specimens, with narrow, one comprising one specimen with broader serrated amphidisc-anchors. In view of the difference in the anchor-breadth of these amphidiscs, I name the former tenuis, the latter lata. One of the four specimens of var. tenuis differs somewhat from the other three; I therefore distinguish two forms, A and B, in this variety. Form A comprises three specimens, form B one. Shape and size. All the specimens (Plate 75, figs. 28-30; Plate 78, fig. 4) are inverted, conical, and more or less flattened laterally. The better preserved ones have a broad and shallow depression on their upper face and a stalk which arises from the lower narrow end. I consider the apical depression a gastral cavity. In one specimen the remnant of a gastral cone is visible in its centre. The specimens are 19-29 mm. long, 23-30 mm. broad, and 8-16 mm. thick. The stalks present are broken off quite short. The longest is 24 mm. long. A few Palythoa polyps are attached to the proximal part of the stalk just below the point where it arises from the body (Plate 75, figs. 29, 30; Plate 76, fig. 7). The colour of all the specimens in spirit is brown. The skeleton. The dermal and gastral surfaces are entirely covered with a dense fur composed of the distal rays of pentactine pinules. In the spicule- preparations a good many diactine pinules were found. These in all probability occupy the margin of the apical (gastral) cavity. In the subdermal and sub- gastral zones radial pentactines and paratangential rhabds are met. Similar rhabds, hexactine megascleres, and microhexactines occupy the interior. Here 252 HYALONEMA (PRIONEMA) AGUJANUM. also occur slender-rayed pentactine and hexactine pinules, and spicules transi- tional between these pinules and the microhexactines. These slender-rayed pinules, and more or less pinule-like transitions to microhexactines, probably occupy the canal-walls, and may be considered as canalar pinules. Acantho- phores are met with in the basal part of the sponge. These vary greatly in thickness. Most of them are tetractine or diactine. Rhabds transitional between the more slender diactine basal acanthophores and the ordinary rhabds of the upper parts of the body are also abundant here. An exceedingly small minority of the short and stout acanthophores in the basal part of the sponge- body are spined not only at the ends of the rays, but entirely. The skeleton of the stalk is continued quite through the body up to the gastral cone (Plate 76, fig. 7). Where it arises from the lower end of the sponge-body, the stalk consists of about a dozen stout and a number of slender rhabds. Of amphidiscs four kinds can be distinguished: — macramphidiscs, serrated amphidiscs, large micr- amphidiscs, and small micramphidiscs. The large micramphidiscs are rare, the others abundant. The skeleton of the Palythoa (Plate 76, figs. 4-6, 34) consists entirely of acanthophores of the sponge. A large majority of these spicules are very short and stout, and entirely spined. These sponge-spicules form an armour of the whole polyp-colony. They occupy in large masses the lateral walls, the oral face, and the stomatodeum of the individual polyps and the superficial part of the coenenchym. The dermal and gastral pinules (Plate 72, figs. 20-25; Plate 78, figs. 9-11) do not appear to differ from each other appreciably. It is, however, to be noted that the dermal pinules of the basal part of the sponge have, at least in var. tenuis, form A, on the whole shorter distal rays than the other dermal and the gastral pinules. All the gastral and dermal pinules are pentactine. The distal rays are straight and end with a blunt or pointed terminal cone. This cone and the proximal end-part of the distal ray are free from spines. For the greater part of its length the distal ray is covered with nearly straight, mostly rather strongly inclined spines. Generally the spines are simple. Occasionally some of them bear secondary spinelets. The middle-part of the distal ray, together with the spines, is usually nearly cylindrical. The lateral rays are attenuated to- ward the abruptly pointed or blunt end. Distally for one half or two thirds of their length they bear rather large, stout spines. The dermal and gastral pinules of var. tenuis, form B, have more slender distal rays than those of var. tenuis, form A, and var. lata. Apart from this the dermal and gastral pinules of the three groups are very similar. Their dimensions are the following: — • HYALONEMA (PRIONEMA) AGUJANUM. 253 GASTRAL AND DERMAL PINULES OF HYALONEMA (PRIONEMA) AGUJANUM. Distal ray Lateral rays length basal thickness M maximum thickness, to- gether with the spines . h length n var. tenuis form A dermal pinules from the basal part of the sponge 123-258 8-12 28-35 42-52 from the middle and upper part of the sponge 200-311 8-10 30-37 36-48 gastral pinules 251-300 9-11 30-39 40-52 dermal and gastral pinules 123-300 8-12 28-39 36-52 form B 1 dermal and gastral pinules 225-311 7-10 18-30 37-45 var. lata dermal pinules 218-302 7-11 22-36 32-57 gastral pinules 215-300 7-13 25-38 30-50 dermal and gastral pinules 215-302 7-13 22-38 30-57 Besides the dermal and the gastral pinules described above, a considerable number of other pinules were found adhering to the surface or embedded in the superficial parts of the sponge. Some of these have long and bushy distal, and very short lateral rays. In others the distal rays are cpiite short and very slender and the laterals long. The former, which are quite frequent, resemble the pinules of Hyalonema tenuifusum and probably belong to that sponge, which was trawled at the same station; I accordingly consider them as foreign. The latter are rare. They may be proper to the sponge and would, in that case, have to be considered as transitions between the dermal pinules and the rnicro- hexactines. Dermal transitional pinules, if such, have been found in both forms of var. tenuis and in var. lata. The dimensions of the few observed are: — 1 The single specimen of var. tenuis form B is not sufficiently well-preserved for a reliable distinction between dermal and gastral pinules; hence special measurements are not given. 254 HYALONEMA (PRION EM A) AGUJANUM. Distal ray Lateral rays length n basal thickness n maximum thick- ness, together with the spines M length n var. tenuis form A 120-160 3-6 4-10 70-98 form B 225-280 6-7 18-20 60-80 var. lata 176-280 5-8 12-18 54-85 Diactine, probably marginal pinules (Plate 78, fig. 3) have been observed only in the preparations of var. tenuis, form A, and var. lata. Their distal ray is usually pointed, exceptionally reduced in length, and rounded and thickened at the end (Plate 78, fig. 3). It is covered with rather strongly inclined, distally directed, generally nearly straight spines. The proximal ray is usually more or less spiny, and pointed or rounded at the end. A central tyle, the remnant of the (reduced) lateral rays, is always present. It is irregularly spherical or com- posed of four distinct lobes (ray-rudiments). Generally it bears several large spines which point obliquely upward and outward. The dimensions of the diactine pinules are: — Distal ray total length length basal thickness n maximum thickness, to- gether with the spines M length of proximal ray transverse diameter of central tyle M var. tenuis form A 400-610 200-290 5-10 17-20 190-320 16-21 var. lata 410-490 167-260 6-9 26-33 160-260 12-23 Pentactine and hexactine spicules with very slender rays have often been observed in the interior of var. lata. I consider these spicules, which are con- nected with the microhexactines by numerous transitional forms, as canalar pinules. In these spicules one ray is different from, usually longer, rarely shorter, than, the others. This differentiated ray, which is to be considered as the distal, bears oblique, distally directed spines. The other rays are also spiny, but their spines are much smaller and generally situated vertically. The ray to be con- sidered as the distal is 100-170 /x long, 3.5-7 m thick at the base, and in its HYALONEMA (PRIONEMA) AGUJANUM. 255 middle-part, together with the spines, usually about 6 n thick. The rays to be considered as the laterals are 60-120 m long. The proximal ray of the hexactine forms is 70-115 n long. The hexactine and the pentactine forms appear to be fairly equally abundant. The (hypoclermal and hypogastral) pentadines (Plate 72, fig. 19) have smooth, conical, and straight, terminally rounded rays. The proximal ray is 460-900 m long and 17-34 n thick at the base. The lateral rays are 220-500 n long. In the same spicule they are usually very unequal in size, the largest being sometimes as much as twice as long as the smallest. The hexactine megascleres (Plate 72, figs. 26, 27) are regular or, more rarely, two opposite rays are longer than the other four. They measure 0.6-1. 4 mm. in maximum diameter (length), and their straight, conical, blunt rays are 14- 33 n thick at the base. Most of the rhabds of the body are centrotyle amphioxes, but tylostyles have also occasionally been observed. The centrotyle amphioxes are 0.8-3. 3 mm. long and 8-19 m thick near the centre. The central tyle is 11-23 m in transverse diameter, that is 1.5-12 ^ more than the adjacent parts of the spicule. These spicules attain a larger size in var. lata than in var. tenuis. Among the basal acanthophores two kinds can be distinguished: — forms with long and slender rays, and forms with short and stout rays. The spicules of the first kind are all diactine, those of the second kind mon- to pentactine. The long and slender diactine acanthophores are connected by numerous transitional forms with the ordinary rhabds of the upper parts of the body. They are 0.6-1. 6 mm. long, usually 6-9 n thick near the middle, and generally curved or, more rarely, angularly bent. The two rays of the angular forms are usually fairly straight. The curvature or angular bend of these spicules is sometimes very considerable, the latter occasionally such that the angle en- closed by the two rays is nearly a right one. The spined end-parts of the rays are often more or less thickened and often unequal. The following dimensions of a spicule of var. lata may serve as an example of this kind of spicule unequally thickened at the two ends: — -length 1.4 mm., thickness in middle 9 tx, thickness of one end 12, of the other 19 /x- The stout and short mon- to pentactine acanthophores can again be divided into two groups of forms only slightly connected by transitions: — those with rays smooth in their basal part, spined only at the end, and longitudinally less reduced (found chiefly in the sponge) ; and forms with rays spined throughout their length and longitudinally more reduced (found chiefly in the Palyt.hoa). 256 HYALONEMA (PRIONEMA) AGUJANUM. The stout- and short-rayed proximally smooth mon- to pentactine acanthophores (Plate 76, figs. 8-16, 31, 32). The pentactine forms (Plate 76, fig. 32) are rare and have been found only in var. tenuis, form A. They are very much smaller than the others and may perhaps be spicules of another kind. The tetractine forms (Plate 76, figs. 8, 10-13) with four fairly equally developed rays are frequent in all the specimens. Their rays extend in the same plane and enclose angles of 90°. They are usually straight and attenuated towards the end. The triactine forms are not nearly so frequent. They are evidently tetractine- derivates and differ from the true tetractines only by one ray being much reduced or suppressed altogether. Transitions between the tetractines and triactines (Plate 76, fig. 10) are by no means rare. The diactine forms (Plate 76, figs. 14- 16) are frequent. They sometimes possess, besides the two properly developed rays, a rudiment of a third ray (Plate 76, fig. 15). Those without such a rudiment are either centrotyle and spindle-shaped (Plate 72, fig. 14), or simply cylindrical and rather thicker at the ends than in the middle (Plate 76, fig. 16). The mon- actines (Plate 76, fig. 31) are rare. They appear as tylostyles. The dimensions of these spicules are the following: — Only terminally spined, basal spicules with 4 3 2 1 Hyalonema (Piionema) more or less fully developed rays agujanum maximum diameter (length) m thickness of rays ju maximum diameter (length) ft thickness of rays m maximum diameter (length) m thickness of 1 rays m maximum diameter (length) £i thickness of | rays ai maximum diameter (length) m thickness of rays m var. tenuis form A 45 6 167- 240 14-17 230- 295 17-18 117- 320 11-21 194 21 form B 140- 440 11-28 275- 340 15-20 570- 1400 10-20 190 17 var. lata 350- 530 12-14 870 12 all forms and varieties 14 6 140- 530 11-28 230- 870 12-20 117- MOO 10-21 190- 194 17-21 As the entirely spined short-rayed basal acanthophores are sufficiently abundant for proper study and measurements only in the Palythoa, and as only HYALONEMA (PRTONEMA) AGUJANUM. 257 two specimens of var. tenuis, form A, bear Palythoa on their stalk, I shall only describe these spicules of this form. The entirely spined short-rayed acanthophores (Plate 76, figs. 4-6, 17-30, 34) of var. tenuis, form A, are mon- to tetractine. The rays of the tri- and tetrac- tines always lie in the same plane. The rays are cylindrical and rounded, sometimes also thickened at the end. The whole spicule is quite uniformly and densely covered with spines, which arise vertically or more rarely obliquely from its surface. The oblique spines, which invariably point outwards, are confined to the ends of the rays. The spines are straight, conical, 4-6 ju long, and 5-7 ju broad at the base. The entirely spined basal spicules measure 58- 210 ju in maximum diameter (length), and their rays are 14-45 ju thick. It is to be noted that this thickness is by no means always in proportion to the length of the spicule. In the smaller forms, under 85 u in length, the rays are 15-22 n thick; in the intermediate, 85-100 /x in length, they are 14-45 /x thick, and in the larger, over 100 /x in length, they are 15-34 /x thick. In view of the fact that the Palythoa doubtlessly derives the whole of the material wherewith it builds its skeleton from the basal part of the sponge to the stalk of which it is attached, it appears very remarkable that the basally smooth spicules, so frequent in the lower part of the sponge, are relatively so rare in the Palythoa; and that, vice versa, the entirely spined spicules, forming the bulk of the skeleton of the Palythoa, are so rare in the lower part of the sponge. In Hyalonema ( Hyalonema ) grandancora, where the relation between the skeleton of the lower part of the sponge-bocly and the skeleton of the Palythoa is the same, this difference appears to be due to the Palythoa selecting the stoutest and most spiny acanthophores of the sponge as material for building its skeleton. The stalk-spicules (Plate 75, figs. 29, 30; Plate 78, figs. 1, 2), at the point where they arise from the body, are in var. tenuis 180-600 n thick, in var. lata 60-300 yu. All those of var. tenuis appear to be smooth. Only some of those of var. lata are smooth, the others (Plate 78, figs. 1, 2) being provided with annular constrictions, usually much deeper on one side than on the other. These con- strictions have a maximum depth of 12 /x, and follow each other at fairly equal intervals of about 110 fx. They render the outline of the parts of the spicules, where they occur, wavy in appearance. In these regions the axial thread ex- hibits a more or less clearly pronounced thickening at or near the centre of many of the bulging parts lying between successive constrictions (Plate 78, figs. 1,2). Some of the stalk-spicules of this variety are irregularly rounded at the proximal end. In one of them the rounded proximal end is 220 fx thick. 258 HYALONEMA (PRIONEMA) AGUJANUM. Among the microhexactines two kinds can be distinguished: — regular forms with equal rays, and irregular forms with one ray or two opposite rays longer than or otherwise different from the others. Th e regular microhexactines (Plate 72, figs. 16-18; Plate 76, figs. 1-3; Plate 78, figs. 5-7) usually have perfectly straight rays. Very rarely one or the other of the rays is somewhat curved. The rays are conical and sharp-pointed. They bear conical, sharp-pointed spines (Plate 76, fig. 1). The spines on the proximal part of the rays are sparse, vertical, and about 0.6 m long. Distally the spines become more numerous, inclined backwards toward the centre of the spicule, and smaller; those a short distance below the end are 0.3 ^ long. The regular microhexactines of the two forms of var. tenuis are 100-180 n in diameter, of var. lata 110-240 yu. The basal thickness of the rays is in the former 3-5 m, in the latter 3-7 /x. The centre, particularly of the larger microhexactines of var. lata, is often distinctly thickened. The irregular microhexactines are to be considered as forms transitional between the canalar pinules and the regular microhexactines, and in respect to shape and size intermediate between these. The amphidiscs were examined biometrically in the usual manner. I measured 238 of var. tenuis, form A; 66 of var. tenuis, form B; and 142 of var. lata. To make these three sets of measurements directly comparable I multi- plied the numbers of amphidiscs of the same length-category of var. tenuis, form B, with 238:66 = 3.606, and of var. lata with 238:142 = 1.677. The numbers thus obtained are the ones used in constructing Figure 12. Morphologically two main groups of amphidiscs are to be distinguished : — amphidiscs with serrated anchor-teeth, more slender shafts, and narrow anchors; and amphidiscs with smooth anchor-teeth, stouter shaft, and broader anchors. The amphidiscs of the first group, which I designate serrated amphidiscs, vary very considerably in size, their length ranging from 90 to 415 /u. The curves representing the frequency of the serrated amphidiscs of different lengths show numerous ups and downs, thus indicating that the serrated amphidiscs of differ- ent size differ in frequency. The irregularities of these curves are, however, hardly of a kind to allow of a distinction of different kinds of serrated amphidiscs according to their size. This is particularly noticeable in the curve of var. tenuis, form A. And as this curve is the most reliable one, on account of its being based on a much larger number of individual measurements than the curves of var. tenuis, form B, and var. lata, I refrain from subdividing the serrated amphidiscs into subgroups. Number of AmphidiscS Fig. 12. — Amphidiscs. Micramphidiscs and ) var tenuis_ Serrated amphidiscs of > p a Macramphidiscs of S Micramphidiscs and ) my_ tmu^ 260 HYALONEMA (PRIONEMA) AGUJANUM. It is different with the amphidiscs with smooth teeth, stouter shaft, and broader anchors. There is a great gap in the length frequency-curve of these spicules in all the three forms: — in the var. tenuis, form A, curve between 80 and 225 m; in the var. tenuis, form B, curve between 78 and 200 /x; and in the var. lata curve between 64 and 207 /x. This clearly divides these spicules biometri- cally into two groups: — macramphidiscs over 200, and micramphidiscs under 80 /x in length. Besides one well-pronounced main elevation each of the three length fre- quency-curves of the macramphidiscs shows only a quite insignificant secondary elevation. The macramphidisc group can therefore be considered as fairly homogeneous. The micramphidiscs on the other hand show clearly pronounced gaps in the length frequency-curves; in the var. tenuis, from A, curve between 30 and 51 /x; in the var. tenuis, form B, curve between 33 and 47 n; and in the var. lata curve between 26.8 and 47 /x. These gaps divide them into two distinct groups, one comprising the micramphidiscs over 47 /x in length, the other the micramphidiscs under 33 m in length. For this reason, and because the former are also distin- guished from the latter by their shafts, which in the larger ones are provided with a relatively very large central tyle, and which in the smaller ones are not thickened at all, or only slightly so at or near the centre, I divide the micram- phidiscs into two secondary groups : — large micramphidiscs with well-developed central tyle, and small micramphidiscs with no central thickening or only a slight one. Thus four kinds of amphidiscs are to be distinguished: — macramphidiscs, serrated amphidiscs, large micramphidiscs, and small micramphidiscs. The normal macramphidiscs (Plate 73, figs. 1-7; Plate 75, figs. 3-21; Plate 77, figs. 1,9, 10; Plate 78, figs. 12-15) have a straight and stout cylindrical shaft, slightly thickened at or near the middle to a central tyle. A verticil of stout and short, distally attenuated, truncate spines arises from this tyle. The number of spines forming the verticil is variable but never great, most frequently four to eight. The verticil is regular or irregular. Its irregularity is usually slight, rarely considerable. In the latter case there are more than eight spines. The remaining parts of the shaft are either quite smooth or they bear only a few scattered spines nearly as broad as the spines of the central tyle, but usually much shorter. The terminal anchors are composed of eight teeth quite uniformly curved throughout (Plate 73, figs. 4, 6) or more strongly bent at the ends than elsewhere (Plate 73, fig. 5). Their curvature is such that the end-parts of the teeth are HYALONEMA (PRIONEMA) AGUJANUM. 261 either parallel, or slightly convergent or divergent. The teeth have the usual T-shaped transverse section. Their upper (outer) band-shaped part arises from the margin of a transverse circular disc situated at the end of the shaft. The diameter of this disc is a little less than a third of the anchor-breadth. In apical views of the anchors, the basal parts of adjacent teeth appear connected by the interdental parts of this disc as by a web (Plate 77, fig. 10). The upper band-shaped part of the teeth is 22-27 n broad at the base and in the middle. It is attenuated distally and pointed at the end. The contour of the tip of the tooth has the shape of a gothic arch (Plate 73, figs. 1-3; Plate 77, fig. 9). The macramphidiscs have on the whole narrower anchors and attain a considerably larger size in var. tenuis, form A, than in var. tenuis, form B, and in var. lata. Their dimensions are as follows : — - NORMAL MACRAMPHIDISCS. Hyalonema ( Prionema ) agujanum var. tenuis var. lata. form A. form B. Total length limits fx 225-440 200-350 207-370 most frequently about ix 387 320 320 Shaft, thickness ix 20-27 18-22 19-25 Central tyle diameter /x 28-43 26 24-34 difference between diameter of tyle and adjacent parts of shaft ix 4-19 5 2-11 Spines of central tyle length n 5-15 9 4-7 basal thickness ix 8-11 10 5-9 Anchor length, limits ix 63-110 55-83 65-95 breadth, limits n 116-172 119-160 112-168 Proportion of anchor-length to anchor-breadth . limits 100 : 143-221 171-236 155-211 average 100: • 169 1 196 186.8 Proportion of anchor-length to total length of whole spicule limits 1 : 3. 9-5. 4 4. 2-4. 9 3.1-5 average 1: 4.7 4.7 4.2 262 HYALONEMA (PRIONEMA) AGUJANUM. In var. tenuis, form A, I found a remarkable abnormal amphidisc (Plate 75, figs. 35-37), 224 n long with a straight shaft 20 \x thick. One of the terminal anchors is quite regular, 90 m long and 112 m broad; the other is somewhat irregular, and partly spirally twisted. Two large protuberances about 50 ^ long arise from the rather eccentrically situated “central” tyle of the shaft. One of these terminates in a broad and thin lamella extending in a radial plane which passes through the axis of the spicule. The distal part of this lamella is strongly and abruptly bent, so as to become parallel to the shaft (Plate 75, fig. 35). The other protuberance of the central tyle terminates in a stout oblique spine. If we mentally construct an ovoidal (rotation-ellipsoidal) surface following the outer sides of the teeth of both anchors and entirely enclosing the whole spicule, we find that the large protuberances of the central tyle reach this surface and abruptly bend on reaching it. This indicates that such an ideal rotation- ellipsoidal surface formed a real limit to their radial growth. This limit may very likely be the surface of a cell ovoid in shape. If this be so, we might assume that the amphidisc was formed and grew within this cell, and that the outer band- shaped parts of its anchor-teeth and the distal bent parts of the protuberances of the central tyle were developed in the superficial part of the protoplasm of this cell. Thus the appearance of this abnormal macramphidisc is in favour of the view that each amphidisc is produced, like the sigms and cheles of the monax- onid sponges, in an ellipsoidal cell, the shape of the surface of which determines the shape and position of the anchor-teeth, which are formed and which grow in its superficial part. The serrated amphidiscs (Plate 74, figs. 1-9; Plate 75, figs. 1,. 2, 22, 23; Plate 76, figs. 33, 35, 36; Plate 77, figs. 2-7) have a rather slender, straight or, rarely, slightly bent (Plate 74, fig. 5) shaft. The shaft is considerably thickened at or near the middle to a conspicuous central tyle. A verticil of long, more or less, often very considerably curved, cylindroconical and truncate or terminally rounded spines arises from the central tyle. In an abnormal serrated macram- phidisc of var. tenuis, form A, the spines of the central tyle are in shape and position similar to the teeth of the terminal anchors, only smaller. One of the terminal anchors of this spicule (the other is broken off) is 117 m long and 75 ^ broad; the anchor-shaped spine-verticil of the central tyle is 61 m long and 55 m broad. The remaining parts of the shaft are covered rather densely with minute spines. These increase in number and in size towards the ends of the shaft. The terminal anchor usually consists of eight teeth. The individual teeth are generally curved in the same direction, concave to the shaft, throughout their length. More rarely a portion of a tooth is curved the other way, convex to the HYALONEMA (PRIONEMA) AGUJAN^IM. 263 shaft (Plate 74, fig. 3; Plate 77, figs. 2, 3). The end-parts of the teeth are often bent rather abruptly inward and they generally converge. The teeth have the usual T-shaped transverse section. Their outer and upper band-shaped part is, in the larger serrated amphidiscs, nearly uniformly (18-22 M) broad throughout, attenuated only slightly distally, and rounded at the end. The lateral and termi- nal margins of the teeth are bent down shaftwards and serrated. The serration- teeth are triangular, sharp-pointed, and usually directed more or less backwards. The lateral ones are 1.5-2 p long and 1-2 n broad, the terminal ones smaller. In var. tenuis, form A, and in var. lata the serrated amphidiscs attain a larger size than in var. tenuis, form B; and in var. lata the average relative breadth of the anchors is considerably greater than in the two forms of var. tenuis. The dimensions of the serrated amphidiscs are : — SERRATED AMPHIDISCS. var. tenuis. var. lata form A form B Total length limits fi 90-410 100-342 90-415 most frequently about ij. 320 103, 180 149, 198, 264 1 Shaft, thickness /x 3-12 5. 5-7. 5 3.5-8 Central tyle diameter ix 6-17 12-15 6-14 differences between diameter of tyle and adjacent parts of shaft n 2.5-10 6-8 2-7.5 Spines of central tyle length ix 5-15 8-12 5-10 basal thickness ix 1.2-4 1.5 1-2 Anchor length, limits /x 30-159 30-145 60-165 breadth, limits /x 20-120 25-118 48-154 Proportion of anchor-length to anchor-breadth limits 100: 63-106 55-83 63-105 average 100 : 71.8 70.4 83 Proportion of anchor-length to total length of the whole spicule limits 1: 2-2.4 2. 2-2. 4 2.2-2. 4 average 1 : 2.3 2.3 2.3 1 When there are two or more numbers in this zone it indicates that the length frequency-curve pertaining to the spicules of the variety or form has more pronounced elevations than one; in these the serrated amphidiscs do not appear to be biometrically homogeneous groups, 264 HYALONEMA (PRIONEMA) AGUJANUM. The rare large micramphidiscs have a stout shaft with an exceptionally large, usually somewhat irregular, central tyle. This tyle bears numerous minute and slender spines. These are not arranged in a verticillate manner, but are scattered over the whole tyle. The remaining parts of the shaft also bear minute spines. The anchor-teeth, which arise nearly vertically from the end of the shaft, are curved quite uniformly throughout, through an angle of about 90°, so that their end-parts are nearly parallel. The dimensions of these amphidiscs are : — LARGE MICRAMPHIDISCS. var. tenuis var. lata form A form B 1 Total length limits ju 51-80 47,78 47-64 most frequently about m 75 50, 60 Shaft, thickness p 1.3-3 1.7-2. 5 Central tyle diameter n 4-7 3.5 5.5 differences between diameter of tyle and adjacent parts of shaft m 2.7-4 3-4 Anchor length, limits p 18-39 13,35 18-24 breadth, limits p 17-31 11,26 14-20 Proportion of anchor-length to anchor-breadth limits 100: 67-100 74-85 78-83 average 100: 82.5 79.5 80.5 Proportion of anchor-length to total length of the spicule limits 1: 2-3 2.2, 3.7 2.3-3 average 1: 2.5 2.9 2.7 The srnall micraviphidiscs (Plate 75, figs. 24-27, 31-34; Plate 77, fig. 8) have a straight shaft, which is either simple, cylindrical, and without any trace of a central tyle, or, more rarely, slightly thickened at or near the centre to a small central tyle. Such central tyles on the shaft are much more frequent in the small micramphidiscs of var. lata than in those of var. tenuis. The shaft is covered throughout with more or fewer, sometimes very numerous minute spines. Only two seen. HYALONEMA (PRIONEMA) AGUJANUM. 265 The spines are vertical, or inclined toward the centre of the spicule. The anchor- teeth arise vertically from the end of the shaft, and are uniformly curved through an angle of about 90°, so that their end-parts are nearly parallel. The dimensions of the small micramphidiscs are: — - var. tenuis var. lata form A form B Total length limits /u 20-30 18-33 18-26.8 most frequently about m 24.5 24.5 20, 24.5 Shaft, thickness n 0.8-1. 3 1-1.5 Anchor length, limits n 5-8.5 4-12 5-7.5 breadth, limits m 6-9.5 6-9 7-8.5 Proportion of anchor-length to anchor-breadth limits 100: 93-160 75-200 100-160 average 100: 122 107 127 Proportion of anchor-length to total length of the whole spicule limits 1 : 2. 9-4. 9 2. 5-5. 9 2. 9-4. 4 average 1: 3.8 4 3.6 The above description shows that these sponges are similar enough to be considered one species. The greater average relative breadth of the serrated amphidiscs, particularly the larger, and some other peculiarities in one of the specimens, call for the recognition of two varieties: — var. tenuis with narrower serrated amphidisc-anchors, and var. lata with broader. One of the four speci- mens of var. tenuis has much smaller macramphidiscs than the others, and I consequently distinguish two forms in it : — A with larger, and B with smaller macramphidiscs. The nearest ally of Hyalonema ( Prionema ) agujanum appears to be the sponge I describe as Hyalonema ( Prionema ) pinulifusum (p. 284). From this it differs by the shape of the macramphidiscs and particularly by the pinules; in H. ( P .) agujanum the distal rays of the largest pinules (together with the spines) are rather slender and more or less cylindrical, in H. ( P .) pinulifusum they are very stout and spindle-shaped. 266 HYALONEMA (PRIONEMA) AZUERONE. Hyalonema (Prionema) azuerone, sp. nov. Plate 56, fig. 1; Plate 57, figs. 1-23; Plate 58, figs. 1-22. One specimen of this species was trawled in the Eastern Pacific at Station 4621 on 21 October, 1904; 6° 36' N., 81° 44' W. ; depth 1067 m. (581 f.); it grew on a bottom of green mud and rock; the bottom-temperature was 40.5°. The Station is off the southern coast of western Panama, southwest of the Azuero Peninsula, to which the name refers. Shape and size. The specimen (Plate 56, fig. 1) appears as a soft and resilient disc with irregular lacerated margin. It is 275 mm. long, 255 mm. broad, 15-25 mm. thick, and forms (probably the greater) part of a sponge which may have been broad and low cup- or vase-shaped, perhaps similar to Hyalonema populi- ferum F. E. Schulze.1 Fragments of large stalk-spicules, and slight remnants of a protuberance indicate that a stalk was present in the living sponge, which arose from the face bearing the protuberance. This face must be considered as dermal. The sponge consists of a mass of curved lamellae, mostly 2-3 mm. thick, and joined to form a labyrinthic structure with elongate cavities or canals, which have a maximum width of 11 mm. The colour in spirit is reddish brown. General structure and canal-system. In those regions of the lower (dermal) surface where the superficial parts are intact, broad, oval pores covered by a fine network are observed. One of these pores (Plate 58, fig. 4) measures 3.8 by 3.4 mm. The network covering it consists of straight threads 30-40 n thick. The nodes are considerably thickened; the meshes are triangular or irregularly square, and 30-120 m wide. The flagellate chambers are curved, irregular sac- shaped, and 80-140 n wide. They form groups surrounding efferent canals and lie, within these groups, close together. The chamber-groups are attached to and held in position by a network of threads, spread out between them and the superficial membranes of the sponge-lamellae in which they lie. The skeleton. The intact parts of the superficial (dermal and gastral) membranes are covered by a dense fur of pinules (Plate 58, figs. 3a, 10, 11). Small patches of the same pinule-fur also occur at the thickened nodes of the nets covering the afferent pores (Plate 58, fig. 4). Pinules are likewise met in the walls of some at least of the canals (Plate 58, fig. lb). These canalar pinules are, however, not nearly so densely crowded as the superficial ones. Rhabds extend F. E. Schulze. Amerikanische Hexactinelliden, 1899, taf. 2, fig. 7. IiYALONEMA (PRIONEMA) AZUERONE. 267 paratangentially in the superficial membranes and occupy, singly or in bundles of two or three, the axes of the threads of the nets covering the afferent pores. Similar rliabds traverse the choanosome, singly or in bundles, in various directions. Most of these rhabds are centrotyle isoactine amphioxes. In some, one actine is reduced in length and terminally thickened ; these resemble tylostyles. Pentac- tine megascleres occur in the superficial parts of the lamellae. In the interior a few hexactine forms are found. Very numerous microhexactines and a few pentactine and diactine-derivates of these spicules are also found in the interior. Seven kinds of amphidiscs occur in this sponge : — not very numerous macramphi- cliscs with serrated anchor-teeth; very rare large mesamphidiscs with smooth teeth; very numerous medium mesamphidiscs, which, in places (Plate 58, fig. 2), form quite dense masses; a few similar small mesamphidiscs; numerous slender- shafted regular micramphidiscs ; and two kinds of micramphidiscs, a larger and a smaller, which are stout- shafted, and generally more or less irregular. The superficial {dennal and gastral ) pinules (Plate 58, figs. 3a, 10, 14, 15, 17, 18, 20-22) observed were all pentactine. The distal ray is straight, 190-390 m long, and 5-9 m thick at the base. It ends with a very slender sharp-pointed terminal cone, and the whole of it, with the exception of its proximal and distal end-parts, is beset with spines. These spines are numerous, rather crowded and longest in the middle-part of the ray; they decrease in size both proximally and distally. The lowest arise nearly vertically; distally they become more and more inclined towards the tip of the ray. The longest spines of the middle- part of the ray usually enclose angles considerably less than 45° with the axis of the ray. These spines are conic, sharp-pointed, attain 25 m in length, 3 m in thickness, and are slightly curved, concave towards the tip of the ray. They are either simple, or bear one or two outwardly directed branch-spines, which sometimes reach a very considerable size (Plate 58, fig. 18). The maximum thickness of the distal ray, together with the spines, is 22-36 m- The basal half of the lateral rays (Plate 58, figs. 14, 15) is nearly cylindrical and smooth, the distal half conic and provided with somewhat sparse, quite large, broad, and low spines. The end is blunt. The lateral rays are 25-55 /z long. They appear to be longer in the gastral than in the dermal pinules; in the former they are usually about 40 m long, in the latter about 30 n. The canalar pinules (Plate 58, figs, lb, 16, 19) are on the whole similar to the superficial ones but have more slender rays, a shorter distal ray, and fewer and smaller spines on the latter. It is also to be noted that they are not all pentactines, a few hexactine forms occurring among them. The measurements 268 HYALONEMA (PRIONEMA) AZUERONE. of these spicules are: — -distal ray, length 134-290 n, basal thickness 4-5 n, maximum thickness together with the spines 13-28 ix; lateral rays, length 26- 52 ix ; proximal ray (when present) , length 35-38 /x. The hexadine megasderes measured were 0.7-2. 4 mm. in diameter, and had smooth, conic, blunt-pointed rays, 17-45 m thick at the base. The pentadine megasderes measured had straight rays, 10-25 fx thick at the base. The proximal ray is 0. 1-0.6 mm. long; the lateral rays, which enclose angles of about 80° with the proximal, are 150-300 n long. The fairly isoadine centrotyle amphiox rhabds are more or less, often very considerably curved, particularly the long ones. They are usually blunt-pointed, near the end sometimes wavy in outline, 0.6-2. 8 mm. long, and 9-25 m thick in their middle-part. The central tyle is 12-28 n in transverse diameter, the proportion between the thickness of the adjacent parts of the spicule and the thickness of the tyle being 100 to 108-151, on an average 100 : 120.6. The tylostyle-like anisoadine centrotyle rhabds are 1-2.5 mm. long, usually slightly curved, and 13-15 /x thick near the morphological centre. Their central tyle measures 14-16 ix in diameter. The terminal thickening (tyle) of the reduced ray is 17-20 n in diameter. Besides the intact tylostyle-like spicules, the measurements of which are given above, some fragments of them with a terminal tyle sometimes 23 fx in diameter were observed. The microhexadines (Plate 57, figs. 18-23; Plate 58, fig. lc) measure 50-160 n in diameter, usually 70-110 /x. The rays of the same spicule are gen- erally equal. They are smooth, at the base 1-3.5 ix thick, usually about 1.8 n, straight in their proximal part and generally slightly curved in their distal part. Their curvature appears to be, on the whole, in inverse proportion to the size of the spicule; the largest microhexactines, that is those more than 125 fx in diameter, having nearly straight rays. One of the microhexactines observed had a bifurcate ray (Plate 57, fig. 20). The rare micropentadines measured were 94-150 ix in diameter, and had rays 1.5-3 m thick at the base. One of the rare diadine microhexadine-derivates measured consisted of two straight rays forming an angle of 85°. Its rays are 3 n thick at the base; one is simple and 60 m long, the other bifurcate and 50 ix long. The amphidiscs. According to their shape, four kinds of amphidiscs are to be distinguished : — A large amphidiscs with relatively short anchors and serrated anchor-teeth; B medium amphidiscs with relatively long anchors and smooth anchor-teeth; C small amphidiscs with slender shafts and relatively HYALONEMA (PRIQNEMA) AZUERONE. 269 small regular anchors; and D small amphidiscs with stout shafts and relatively large, usually more or less irregular anchors. Biometrically, according to the length frequency, A is a well-defined, simple, and homogeneous group. B overlaps C and D somewhat, and C and D are about equal in length. B is biometrically composed of three secondary groups represented by (a), large, (6), medium sized, and (c), small amphidiscs. C is biometrically a simple and homogeneous group. D is biometrically composed of two well-defined secondary groups represented by larger amphidiscs (a), and smaller amphi- discs (6). Thus if both their shape and the biometric character of their length- frequencies are taken into consideration seven kinds of amphidiscs are to be distinguished: — macramphidiscs (A); large mesamphidiscs ( B a) ; medium mesamphidiscs (B b ) ; small mesamphidiscs (B c) ; slender-shafted micram- phidiscs (C); stout-shafted large micramphidiscs (Da); and stout-shafted small micramphidiscs ( D b) . The macramphidiscs (Plate 57, figs. 1-5; Plate 58, figs. 5-9) are 300-356 /x long, most frequently about 320 n. Their shaft, which is straight and for the most part 7-9 thick, thickens at the ends gradually to a conic extension 10-14 n in diameter, and in or near the middle abruptly to a central tyle of the same diameter. The proportion of the thickness of the adjacent parts of the shaft to the thickness of the central tyle is 100 to 130-200, on an average 100 : 157.4. An irregular verticil of cylindroconic, truncate, or terminally rounded spines arises from the central tyle. These spines are 1.5-3. 5 n thick, usually 1.5-4 n long, sometimes as much as 8 n, and when long are irregularly curved. They bear on their terminal face a cluster of exceedingly minute secondary spinelets. Scattered spines, similar to those of the central tyle, but on the whole shorter, are met on the remaining parts of the shaft. The terminal anchors are 77- 119 m long; they are broadest usually a little over a third of the whole spicule, somewhere beyond the middle, and attenuated towards the end. Their maxi- mum breadth is 85-104 m, their end-breadth 75-95 /x. The proportion of length to maximum breadth is 100 to 77-114, on an average 100 : 101.5. The maxi- mum breadth is 3-11 on an average 7.1 m, greater than the end-breadth. The anchor usually consists of nine or ten teeth. The individual teeth arise steeply from the end of the shaft, and are strongly curved in their basal part. Farther on the curvature decreases either gradually or somewhat abruptly. The decrease of curvature either continues to the end of the tooth, or it increases again just before the end. The total curvature is such that the end-parts of the teeth converge toward the shaft, with the axis of which they usually enclose 270 HYALONEMA (PRIONEMA) AZUERONE. an angle of 10°-20°. The teeth have the usual T-shaped transverse section. The lower, radial part, corresponding to the upright stroke of the T, extends to the end of the tooth. The upper, paratangential part, corresponding to the upper, horizontal stroke of the T, is 12-16 n broad in its middle-part and grad- ually attenuated distally; its end is broad and simply rounded; its lateral margins are strongly serrated (Plate 58, figs. 5-9). The individual saw-teeth are pointed and usually triangular. In the middle-part of the anchor-tooth these saw-teeth are 1-2 m long and close together. Distally they become smaller and more distant; at the end they are only about 0.5 n long. The saw-teeth are directed obliquely inward. A similar serration of the teeth was found also in H. spinosum (p. 276) and in a few others. In a few of the macramphidiscs observed two or three supernumerary shaft-rudiments arose from the central tyle. In one of them, two of these rudiments bore somewhat reduced and irregular terminal anchors. The large mesaviphidiscs (Plate 57, fig. 8) are very rare; the one represented is 232 n long. Its shaft is 5.5 n thick and its central tyle 8 m- A verticil of spines, with a maximum length of 4 n, arises from the latter, and numerous short and broad spines cover the remaining parts of the shaft. The terminal anchors are semioval, 108 m long, and 72 m broad; the proportion of their length to their breadth being 100: 67. The medium mesamphidiscs (Plate 57, figs. 6, 7; Plate 58, figs. 2, 13) are very numerous. They measure 56-130 m in length, most frequently about 85 m- Their shaft is 1.3-3 m thick and abruptly thickened in or near the middle to a central tyle 1.5-5 m in diameter. The proportion of the thickness of the shaft to that of the tyle is 100 to 140-220, on an average 100 : 165.4. A verticillate bunch of irregularly curved, obtuse spines 1-3.5 m long arises from the tyle. Similar, usually much shorter spines are scattered in greater or smaller numbers irregularly over the remaining part of the shaft. The degree of spinulation of the shaft is correlated with, and in proportion to, the size of the spicule; the larger the amphidisc the larger and the more numerous the spines. The anchors are 15-46 m long, one third to nearly half of the whole spicule, and 12.5-31 m broad. The proportion of their length to their breadth is 100 to 57-83, on an average 100 : 68.6. This proportion is correlated to the size of the spicule, the anchors being on the whole relatively the narrower, the larger the spicule (the anchor). The average proportion of length to breadth of the anchors under 20 m in length is 100 : 80.5, of the anchors under 30 m in length 100: 72.3, and of the anchors over 40 m in length 100 : 65.9. The anchors usually consist of twelve or thirteen 271 HYALONEMA (PRIONEMA) AZUERONE. teeth. The individual teeth arise nearly vertically, are strongly and usually somewhat abruptly bent a short distance from their point of origin, and only slightly curved, concave to the shaft in their distal and middle-parts. The curvature is usually such that the end-parts of the teeth diverge from the shaft at angles of about 6°. Rarely the teeth are more strongly curved, so that their end-parts become nearly parallel to the shaft and to each other. The end-parts of such teeth are either straight or slightly curved outwards. The small mesamphidiscs are rare. They connect the medium-sized mesam- phidiscs described above with the slender-shafted micramphidiscs described below. The small mesamphidiscs are usually about 44 n long, have shafts about 1.5 n thick, and anchors measuring 15-18 n in length and 11-16 n in breadth. The average proportion of anchor-length to anchor-breadth is 100: 81. The large stout-shafted micramphidiscs (Plate 57, fig. 9) are 38-68 n long, most frequently about 43 n. The shaft is straight, 1.8-2. 5 n thick, for the greater part of its length, and abruptly thickened in or near the middle to a more or less irregular central t.yle, usually 4-6 n in diameter, sometimes as much as 8 m- The proportion of the thickness of the shaft to that of the t.yle is 100 to 160-320, on an average 100:239.8. The whole of the shaft, including the central t.yle, is more or less spiny. The spines of the t.yle are generally larger than the others and arranged in a verticil] ate manner. The anchors are usually irregular, the teeth on one side often being considerably longer than those on the other. The two anchors of the same spicule usually have the longest teeth on opposite sides, exceptionally on the same side. The maximum length of the anchor, that is the anchor-length on the side where the teeth are longest, is 15-42 /x, sometimes more than half the length of the whole spicule. On the opposite side the anchor is usually 4-10 /x shorter. The breadth of the anchors is 8.4-21 The propor- tion of the maximum length to the breadth is 100 to 45-91, on an average 100: 66.4. The individual teeth arise vertically from the end of the shaft, and are strongly curved in their basal part. Farther on the curvature decreases and their end-parts are curved only slightly, concave to the shaft, or are straight, or even curved slightly in the opposite direction. In no case do the end-parts of the teeth diverge much from a direction parallel to the shaft, either one way or the other. When, as sometimes happens, the longest teeth of the two opposite anchors lie on the same side of the spicule and are, both together, longer than the whole spicule, their end-parts lie side by side, but do not, coalesce. The small stout-shafted micramphidiscs (Plate 57, figs. 10-12) are 23-34 ^ long, most frequently about, 32 They are similar to the large ones, but have 272 HYALONEMA (PRTONEMA) AZUERONE. more spiny shafts and relatively smaller and, on the whole, still more irregular anchors. The shaft is for the most part 1.2-2 n thick, and abruptly thickened in or near the centre to a remarkably large central tyle which measures 2-5 m in diameter. The remainder of the shaft is often not quite uniform in thickness. The proportion of the thickness of the shaft to that of the tyle is 100 to 133-333, on an average 100: 204.8. The whole of the shaft, including the central tyle, is beset with very numerous spines. Those on the tyle are either large and ar- ranged in a verticillate manner, or small and quite uniformly scattered over the whole tyle. Those on the remaining parts of the shaft are always small. The maximum length of the anchors is 7-12 /x, about a third of the length of the whole spicule, their breadth 8-12 n. The proportion of maximum length to breadth is 100 to 73-125, on an average 100 : 101.3. The individual anchor-teeth are curved so that their end-parts do not greatly diverge from a direction parallel to the shaft. The slender-shafted micramphidiscs (Plate 57, figs. 13-17; Plate 58, fig. 12) are 30-58 n long, most frequently about 42 n- The shaft is regularly cylindrical, straight or, rarely, slightly curved, 1-1.7 m thick, and thickened at some point, sometimes a long way from the middle, to a central tyle 1.4-2. 4 \x in diameter. The proportion of the thickness of the shaft to that of the tyle is 100 to 114-131, on an average 100 : 121. A few blunt spines, sometimes 0.7 \i long, arise from the tyle. The remainder of the shaft is usually quite smooth. In a few, particu- larly in the large and slender-anchored ones, the shaft bears minute spines. The anchors are regular, 6-10 n long, a quarter to a sixth of the whole spicule, and 9-10 n broad. The proportion of their length to their breadth is 100 to 105-150, on an average 100 : 121 .6. The number of teeth in the anchor is about seventeen. The individual teeth arise vertically and are considerably curved in their basal part. Distally the curvature decreases in a uniform manner. The end-parts of the teeth diverge more or less from the shaft. The large slender-anchored forms above referred to connect these amphi- discs with the small mesamphidiscs. The nearest ally of the sponge above described among the species hitherto made known appears to be Hyalonema validum F. E. Schulze. With this species it coincides in respect to the shape and size of all the spicules, with the excep- tion of the stout-shafted more or less irregular micramphidiscs, which are present in H. (P.) azuerone and absent in H. validum; the microhexactines, which have more strongly bent rays in the latter than in the former; and the dermal pinules, the distal rays of which are bushy and have a thick, abruptly pointed HYALONEMA (PRIONEMA) SPINOSUM. 273 terminal cone in H. valid am, and are slender and have a very slender and fine- pointed terminal cone in H. (P.) azuerone. Hyalonema (Prionema) spinosum, sp. nov. Plate 48, figs. 1-31 ; Plate 49, figs. 1-23; Plate 50, figs. 1-5. Three specimens of this species were trawled nearly under the equator in the Eastern Pacific at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W.; depth 4243 m. (2320 f.) ; they grew on very light, fine Globigerina ooze; the bottom-temperature was 34.3°. The microhexactines bear unusually large spines. To this the specific name refers. Shape and size. The largest specimen (Plate 48, fig. 12) is a lamella or plate, roughly round in outline when spread out flat. It is 46 mm. long, 37 mm. broad, and has a fairly uniform thickness of 8-10 mm. The margin is rounded. The lamella is folded along a straight line passing nearly through its centre. The two parts on either side of the fold are flat, and enclose an angle of about 70°. On the convex side of the fold a rounded protuberance arises near the margin. In life, the stalk, which is now, however, entirely absent, arose from this. At the opposite end of the fold the margin is slightly incised. On the con- vex surface of the lamella, which is the dermal, the covering (dermal) membrane is lost in many places, and this side consequently appears rough and porous. On the opposite, concave side, which is the gastral, meandric branching grooves are observed, which, on the whole, radiate from a point in the fold near the centre of the lamella. At this point a small and slender gastral cone arises from the concavity of the fold. One of the smaller specimens (Plate 48, fig. 11) is lenticular in shape. It measures 35 mm. in horizontal diameter and is 16 mm. thick. Near the middle of one (the lower, dermal) face a rounded protuberance arises. From this, in life, the stalk, which is now absent, protruded. In respect to the structure of the surface this specimen resembles the large one. The other small specimen is fragmentary and measures 25 by 22 by 8 mm. The colour of the two better preserved specimens is, in spirit, light brown; of the fragmentary one, whitish. The lamellar or lenticular sponge-body is traversed by wide canals (Plate 48, fig. 13), most of which extend in a more or less vertical direction. Some of these canals are afferent and open out below, others are efferent and open out above '274 HYALONEMA (PRIONEMA) SPINOSUM. in the gastral surface. The gastral membrane exhibits, in many places, a reticulate structure; in life the mouths of the efferent canals were probably covered with nets. The skeleton. The surface is, so far as the dermal and gastral membranes are intact, covered by a dense pinule-fur (Plate 48, fig. 23). The dermal pinules on the outer (lower, convex) side, and the gastral pinules on the inner (upper, concave) side are very much alike. The gastral pinule-fur extends quite down to the bottom of the grooves above referred to. Lateral, paratangentially situated, rays of large (hypodermal and hypogastral) pentactines extend just below the level occupied by the lateral pinule-rays. In the gastral membrane numerous paratangential amphioxes accompany them. The proximal rays of the pentactines point radially inward. Large numbers of stout acanthophores, tetractine to monactine, occur in the protuberance from which, in life, the stalk arose. The interior of the sponge is occupied by dense masses of relatively large microhexactines, which evidently form the main support of the whole sponge- body. Besides these spicules, rhabd and hexactine megascleres and amphidiscs occur in the choanosome. The dermal 'pinules (Plate 48, figs. 17-22) are mostly pentactine, rarely hexactine (Plate 48, fig. 20). The distal ray is 100-154 ^ long, usually 1 17— 138 /d, and 3. 5-4. 5 n thick at the base. It is straight, regularly conic, and not thickened in the middle. The distal end-part of the ray is, for a considerable distance, free from spines. The basal part is also smooth. The remaining parts of it are covered with sparse spines directed obliquely upward. The spines are largest on the middle-part of the ray; they are sometimes 1 1 n and more long, slender, usually only 1-1.3 m thick, basally cylindrical, distally conical, and sharp-pointed. The maximum transverse diameter of the distal ray, together with the spines, is 10-17 id. The lateral rays are straight, sparsely spined in their distal part, and 20-50 m long, usually 25-40 /d. The proximal ray of the hexac- tine forms is smooth and rarely more than 15 m long. The gastral pinules (Plate 48, figs. 23-27) are similar to the dermal and, like these, for the most part pentactine. The distal ray is 100-142 ^ long, usually 105-135 /d, and 3. 5-5. 5 fi thick at the base. Its maximum transverse diameter, together with the spines, is 11-17 id. The lateral rays are 22-35 /x long. The hypodermal and hypogastral pentactines (Plate 49, figs. 12-14) have smooth, blunt, conic rays. The lateral rays enclose angles of 90° or a little less with the apical (proximal) ray. The apical ray is straight, or slightly curved, HYALONEMA (PRIONEMA) SPINOSUM. 275 0.5-2. 8 mm. long, and 20-100 p thick at the base; the lateral rays are straight, and 0.2-1 mm. long. The length of the lateral rays is not in proportion to the length of the apical ray, pentactines with a very long apical ray often having comparatively short lateral rays and vice versa. The hexactine megascleres (Plate 49, fig. 19) have smooth, generally fairly straight, conic rays. The intact ones measured have a maximum diameter of 0.5-1. 5 mm. and rays 12-43 p thick at the base. Some fragments with rays 43 p thick, which I observed, indicated that, these spicules occasionally attain considerably larger dimensions. The acanthophores (Plate 48, figs. 1-10) have one to four straight or, more rarely, curved rays, smooth in their basal part, but covered with spines in their end-part. The rays are conic or, more rarely, cylindrical and blunt-pointed or rounded, and not infrequently thickened at the end. These spicules measure 1 10-430 p in maximum diameter (length) ; their rays are 10-30 p thick at the base. The rays of the tetractine and triactine forms lie in one plane. In the tetractine forms, which are the most frequent, either all four rays are fairly equal (Plate 48, figs. 1,3) or only three, the fourth being more or less reduced in length (Plate 48, figs. 2, 4, 5). In some of these spicules one ray is altogether suppressed. These are the triactines (Plate 48, fig. 6). The diactines usually appear as straight centrotyle rods (Plate 48, figs. 7-9). The rare monactines are tylostyles (Plate 48, fig. 10). Their terminal tyle is obviously homologous to the central tyle of the diactines. The rhabds. The rhabds of the gastral membrane are more or less curved, slightly centrotyle amphioxes, and mostly about 1 mm. long and 8-9 p thick. The central tyle measures 10-13 p in transverse diameter. In the interior simi- lar and also much larger rhabds are met. The largest intact ones observed measured 2.9 mm. by 40 p\ the stoutest rhabd-fragment was 130 p thick. The six rays of the microhexactines (Plate 49, figs. 14-18, 20-23) are, in the same spicule, fairly equal and regularly arranged, each one enclosing an angle of 90° with its neighbours. The microhexactines measure 108-180 p in total diameter, usually 117-148 p. Their rays are straight, 50-90 p long, at the base 4.5-6 p thick, usually about 5 p, conic and sharp-pointed. They bear large and conspicuous, backwardly directed spines. On the proximal half of the ray the spines are 1.2-2. 6 p long, stout, and sparse; on its distal half they are smaller and much more crowded. Among the amphidiscs four kind are to be distinguished: — large macram- phidiscs, small macramphidiscs, large micramphidiscs, small micramphidiscs. 276 HYALONEMA (PRIONEMA) SPINOSUM. The abundant normal large macramphidiscs (Plate 48, figs. 14-16; Plate 49, figs. 7-9, 11 ; Plate 50, figs. 1-5) are 180-298 n long, most frequently about 255 /z. The shaft is usualljr straight, rarely slightly curved, for the most part nearly cylindrical, 3-8 n thick, and abruptly thickened at or near the middle to a central tyle 6.5-17 n in transverse diameter. The proportion of the diameter of the adjacent parts of the shaft to the diameter of the tyle is 1 : 1.3 — 1 : 3.2, most frequently about 1 :2. From the central tyle a verticil of about eight- large spines arises; these are slightly and irregularly curved but on the whole vertical (Plate 48, figs. 14-16; Plate 49, figs. 8, 9, 11). These spines are cylin- drical, rounded or abruptly pointed at the end, and always quite smooth and destitute of secondary spinelets. They are 8-23 n long and 2-3.5 n thick at the base. The parts of the shaft outside the central tyle and its vicinity bear nu- merous low, cylindrical and truncate, wart-like spines, 0.5-1. 5 m high, 1-2 n broad, and circular in outline (Plate 48, figs. 15, 16; Plate 49, figs. 8, 9, 11). From the terminal face of each of these spines a cluster of exceedingly minute secondary spinelets arises. The terminal anchors are 68-107 n long, considerably more than a third of the whole spicule, and 61-117 /x broad. The proportion of length to breadth is 100 : 73-100 : 114, on an average 100 : 94. A correlation between the anchor- proportion and the size of the spicule was not noticed. All the anchors counted were composed of eight teeth. The individual teeth are considerably curved near the base. Distally the curvature decreases. The end is slightly and somewhat abruptly bent inward towards the shaft. The teeth have a T-shaped transverse section. The upper part is band-shaped, 9-13 n broad near the base, very slightly attenuated distally, and rounded at the end. The lower part is a crest projecting towards the shaft. This crest is 5 n high near the base; distally it gradually becomes lower, and it appears to vanish altogether about 10 m from the end of the tooth. The anchor- teeth bear, on their lateral margins, secondary teeth and consequently appear serrated (Plate 49, fig. 7; Plate 50, figs. 1-5). These secondary teeth stand quite close together and extend from the base to within a short distance of the end of the primary tooth, leaving only the rounded end free. The secondary teeth are triangular in outline, 0.5-1. 2 n long, 1-1.5 n broad, sharp-pointed, and directed more or less backwards. They resemble shark’s teeth. Besides the normal spicules above described a few young and also a few abnormally large macrampkidiscs have been observed. The young forms have a slender shaft, a relatively stout central thickening, and short and thin anchor- HYALONEMA (PRJONEMA) SPINOSUM. 277 teeth. One of the abnormal forms is represented on Plate 49, fig. 10. This spicule is 235 m long, its shaft is 5 ^ thick, central tyle 9 m thick. A verticil of short, laterally compressed, distally broadened and truncate, band-shaped spines arises from the tyle. The remainder of the shaft bears short, truncate, cylindrical spines. The anchors are about 54 n long, 33 m broad. The anchor- teeth have serrated margins, are strongly curved in their basal part, but nearly straight in their middle- and end-parts. The latter are nearly parallel to the shaft. Another similar spicule observed was only 180 ^ long. I have also seen a few large macramphidiscs in which the spines on the central tyle were similar to the teeth of the terminal anchors, and all curved in one direction, so that the verticil formed by them was like a terminal anchor, only smaller. The rare small 7nacramphidiscs (Plate 49, figs. 5, 6) differ from the large macramphidiscs — apart from their smaller size — chiefly by being destitute of long central spines. The small macramphidiscs are 45-126 m long. The shaft is 1-3 m thick, and either simply cylindrical (Plate 49, fig. 5) or gradually thick- ened at or near the middle (Plate 49, fig. 6) to a tjde sometimes 5.5 m in transverse diameter. The proportion of the thickness of the adjacent parts of the shaft to the diameter of the tyle is 1 : 1 (when there is no tyle) ; 1 : 2.2 (when the tyle is most highly developed). The whole of the shaft is uniformly and densely covered with small spines. The spines on the tyle are not larger than the others. The anchors are 13-56 ^ long, a third or less of the whole spicule, and 12-43 /! broad. The proportion of the length to the breadth of the anchors is 100 to 77-92, on an average 100 : 86. The individual teeth appear to differ from those of the large macramphidiscs only by being smaller. The large micramphidiscs are very rare. In fact only two could be measured. These are 51 and 56 m long, and have anchors 16 and 19 ^ long and 8.5 and 9 /j. broad respectively. The proportion of length to breadth of their anchors is 100 : 56 and 100 : 44. The small micramphidiscs (Plate 48, figs. 28-31; Plate 49, figs. 1-4) are, although much more abundant than the other amphidisc-forms, still not nearly so frequent as in other hyalonematids. They are 13-29 n long, usually 17-27 n, and have a shaft 0.8-1. 7 m thick. The shaft generally bears a larger or a smaller number of minute, cylindrical, truncate, vertical or oblique spines. These spines are irregularly distributed; often they form a little cluster near the centre of the shaft. The anchors are 4-7.5 n long, a fifth to a third of the whole spicule, and 5-8 n broad. The proportion of their length to their breadth is 100 to 87- 175, on an average 100 : 134.8. The individual anchor-teeth are strongly curved 278 HYALONEMA (PRIONEMA) CRASSUM. in their basal part, but only slightly curved or straight in their distal part. The latter is either parallel to the shaft or diverges from it only slightly. Among the known species Hyalonema solutum F. E. Schulze 1 appears to be the nearest ally of the sponges above described. From this they differ by having much smaller pinules, stouter microhexactine rays, spined macramphi- disc-shafts, and serrated macramphidisc-teeth. The nearest ally appears to be H. (P.) crassum (infra). From this it differs chiefly: — by the absence of macramphidiscs with short and broad anchors and smooth teeth; by the anchors of the serrated macramphidiscs being somewhat differently shaped; by the presence of small macramphidiscs; by the smaller size of the largest micramphidiscs; by the absence of stout paratangential rhabds (tignules) in the superficial membranes; and by having smaller pinules. Hyalonema (Prionema) crassum, sp. nov. Plate 106, figs. 4-37; Plate 107, figs. 1-20; Plate 108, figs. 1-17. A larger and two smaller specimens of this species were trawled nearly under the equator at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W. ; depth 4243 m. (2320 f.); they grew on very light, fine Globigerina ooze; the bottom- temperature was 34.3°. They possess macramphidiscs with remarkably stout shafts and thick superficial amphioxes. To these peculiarities the specific name refers. Shape and size. The largest specimen (Plate 107, fig. 16) has the shape of a low, thick-walled cup, irregularly circular in outline. The cup measures 36 mm. in transverse diameter and is 21 mm. high. Its wall is at the base about 9 mm. thick, near the margin about 6 mm. Its convex, outer, dermal face is fairly smooth. On the inner, concave, gastral face longitudinally (radially) extending grooves make their appearance. The margin of the cup is rounded. Just out- side this rounded margin, where it passes into the outer convex face, a slightly protruding but very distinct crest makes its appearance. This crest, which forms a complete ring round the cup, probably marks the boundary between the dermal and gastral parts of the surface. The two smaller specimens are similar, but more cake-shaped and respec- tively 24 and 21 mm. in maximum diameter. The colour of the sponge in spirit is light dirty brown. The skeleton. All the intact parts of the surface are covered with a dense F. E. Schulze. Hexactinellida. Ergeb. Deutsch. tiefsee-exped., 1904, 4, p. 77, t. 31, fig. 14—22. HYALONEMA (PRIONEMA) CRASSUM. 279 spicule-fur composed of the distal rays of the superficial (dermal and gastral) pinules. The dermal and gastral membranes are supported by the lateral rays of these pinules and of the hypodermal and hypogastral pentactines. Very numerous paratangentially extending amphioxes are also found in them. Many of these spicules are very stout and appear as tignules. Hexactine megascleres, amphioxes, microhexactines, and amphidiscs occur in the interior. The micro- hexactines are exceedingly abundant and appear as dense masses in the sections. They form the chief support of the whole sponge. Of amphidiscs four kinds can be distinguished: — macramphidiscs with smooth teeth, macramphidiscs with serrated teeth, and large and small micramphidiscs. The first- two are not frequent and appear to be confined to the superficial parts of the choanosome. The large micramphidiscs are also rather rare. The small micramphidiscs, on the other hand, are exceedingly abundant and form continuous layers in the walls of some of the canals. The pinules (Plate 106, figs. 26-30) of the dermal and gastral faces of the sponge agree so closely in shape and size that I shall here describe them together. All the pinules observed were pentactine. Their distal ray is straight, 110- 200 m long, most frequently 140-165 n, and 4-5.5 /x thick at the base. The spines it bears are small and not numerous. The longest usually arise from the middle- part of its length, and here the distal ray, together with the spines, attains a maxi- mum diameter of 14-19 m- The lateral rays are spiny, particularly in their distal half, and generally conical and pointed, more rarely cylindroconical and terminally rounded. They are 20-30 /x long, rarely as much as 35 m- In the spicule-preparations I found a few fragments of diadine pinules and one whole pinule. Possibly such spicules occur in the above mentioned crest separating the dermal and gastral parts of the surface. I, however, failed to find any such spicules in situ, so that it appears very doubtful whether the few observed are proper to the sponge. The hypodermal pentactines (Plate 108, figs. 1, 3-5, 8, 9) have a conical, rather blunt-pointed, usually straight, rarely bent apical proximal ray 1-1.7 mm. long, and 27-62 m thick at the base. The lateral, paratangential rays are also blunt conical. Those of the same spicule are often markedly unequal ; the length of the largest is 300-510 m- The hypogastral pentactines (Plate 108, figs. 2, 6, 7) are similar to the hypo- dermal but have on the whole shorter and somewhat stouter rays. Their dimensions are: — length of apical ray 0.75-1.35 mm.; basal thickness of apical ray 30-70 /x ; length of lateral rays 230-320 /x. 280 HYALONEMA (PEIONEMA) CRASSUM. The hexactine megascleres (Plate 108, figs. 10-13) are 0.7-2. 5 n in diameter, and have straight or slightly curved, blunt, conical rays 20-55 /j thick at the base. Three kinds of amphioxes can be distinguished: — large ones, confined to the choanosome; intermediate and small ones, found both radially situated in the choanosome and paratangentially situated in the dermal and gastral membranes; and small stout, paratangentially situated ones, confined to the dermal and gastral membranes. The large amphioxes of the choanosome measured are 2. 5-8. 5 mm. long and 18-80 n thick. These spicules are 90-140 times as long as thick. The intermediate and small slender amphioxes of all parts of the body are 0.67-2.5 mm. long and 10-35 n thick. These spicules are 40-160 times as long as thick. The small stout amphioxes ( tignules ) of the dermal and gastral membranes are 410-980 n long and 13-50 n thick. These amphioxes are 17-39 times as long as thick. A good many of them are distinctly cent rot, yle, the central tyle being sometimes 9 n more than the adjacent parts of the spicule in transverse diameter. The gastral small stout amphioxes (Plate 107, fig. 11) are, on the whole, relatively considerably thicker than the dermal, the former being on an average 23.7 times, the latter 28.4 times as long as thick. Taking all the amphioxes of the sponge together we find that all those under 650 n in length are less than 40 times as long as thick, while all those over 940 n in length measured are, with a single exception, more than 40 times as long as thick. The microhex adines (Plate 106, figs. 4-12, 31-37) are 108-175 n in diameter, on an average about 140 n- The rays of the same spicule are generally equal and regularly arranged, but are exceptionally unequal in length. The rays are straight, conical, sharp-pointed, at the base 4.5-7 n thick, usually 5-6.5 n, and spined. The spines of the proximal part of the ray are sparse, vertical, broad conical, sharp-pointed, and 1.5-2 ^ high. Distally the spines become more numerous and crowded, smaller, more slender, and more and more inclined back- wards towards the centre of the spicule. From the morphological point of view four kinds of amphidiscs can be dis- tinguished:— 1, large ones with thick shaft, broad and short anchors, and smooth teeth; 2, large ones with slender shaft, medium anchors, and serrated teeth; 3, small ones with long and slender anchors; and 4, still smaller ones with medium anchors. Examined biometrically, according to their length frequency, the amphidiscs 20 15 10 5 HYALONEMA (PRIONEMA) CRASSUM. 281 fall into two groups, large and small ones. These two groups are very clearly distinguished, there being no amphidiscs 62-159 n long. This absence of inter- mediate amphidiscs finds its expression in the adjoined graph in the large gap of the curve between 72.89 and 129.13. The amphidiscs the lengths of which are represented by the curves to the right of the gap belong to the morphological groups 1 and 2. The two curves overlap considerably. The amphidiscs to Smooth y Macramphidiscs. Serrated J Micramphidiscs which the curve to the left of the gap pertains are those of the morphological groups 3 and 4. There is a conspicuous depression in this curve at 37.40- 41.14, corresponding to the absence of amphidiscs 37-41 m long. This depres- sion may be taken as the limit dividing the (smaller) amphidiscs of the mor- phological group 4 from the larger ones of group 3. 282 HYALONEMA (PRIONEMA) CRASSUM. I designate the four groups of amphidiscs: — -smooth macramphidiscs (group 1) ; serrated macramphidiscs (group 2) ; large micramphidiscs (group 3) ; and small micramphidiscs (group 4). The smooth macramphidiscs (Plate 108, figs. 14-17) are 290-370 m long, most frequently about 337 n. Their length frequency-curve is narrow and simple, and has a single summit. The shaft of these spicules is straight, cylindrical, 18-30 n thick, usually 20-26 n, and thickened at or near the middle of its length to a central tyle 4-12 n more in transverse diameter than its adjacent parts. Several broad, terminally rounded spines 3-8 n long arise from the central tyle. The remaining parts of the shaft are smooth. The terminal anchors are 55-78 m in length, usually one sixth to one fourth of the whole spicule, and 105-140 ^ broad. The proportion of their length to their breadth is 100 to 155-236, on an average 100 : 174.3. The individual teeth attain their maximum breadth of 20-30 n in their distal part, and are very abruptly pointed, the contour of their end-part having, when seen en face, the shape of a broad gothic arch. The teeth are uniformly curved; the outer con- tour of the anchor when seen in profile is generally nearly semicircular. The serrated macramphidiscs (Plate 107, figs. 1-5, 17-20) are 150-328 n long. Their length frequency-curve is rather broad and irregular, and has three distinct summits. The middle one is quite insignificant ; the other two, situated at about 164 and 240 n respectively, are very pronounced. The shaft of these amphi- discs is straight, 3-6 n thick, and thickened at or near the middle of its length to a central tyle 2-6 n more in transverse diameter than its adjacent parts. The central tyle bears a verticil of cylindrical, terminally rounded, straight or curved spines 5-14 n long. The remaining parts of the shaft are covered with numerous low protuberances (very short spines). The terminal anchors are 61-105 n long, the whole spicule being 2.5 to 3.5 times as long as the anchor. The maximum anchor-breadth is 45-100 n. The end-parts of the teeth of some of these anchors are nearly parallel; in these anch- ors the end-breadth is equal to the maximum breadth; the end-parts of the teeth of others are convergent, — in these anchors the end-breadth is 2-6 ^ less than the maximum breadth. The proportion of anchor-length to anchor-breadth is 100 to 72-102, on an average 100 : 83.6. The individual teeth arise vertically from the shaft, are strongly bent in their basal part, and straight or only slightly curved in their distal part. Their tips are, as mentioned above, parallel or slightly convergent. The teeth attain their maximum breadth of 12-15 /x in their middle-part, and are attenuated HYALONEMA (PRIONEMA) CRASSUM. 283 both towards the base and towards the tip. The end of the tooth is simply rounded. From the lateral margins of the teeth pointed triangular protuberances arise, which stand close together and render these margins serrated. The saw- teeth are, in the middle-part of the tooth, about 1 ^ high, 2 broad, and vertical. Distally they become narrower and smaller and more and more directed back- wards (Plate 107, figs. 17-20). The rounded distal ends of the teeth are smooth. The large micramphidiscs are 42-61 ^ long, most frequently about 52 //. Their length frequency-curve is rather broad and irregular in so far as it exhibits, besides the main summit at about 52 n, another insignificant one at about 63 m- The shaft of these amphidiscs is straight, spiny, sometimes centrotyle, and 1.5- 2.3 m thick. The terminal anchors are 17-22 m long. The whole spicule is 2.2-3 times as long as its anchors. The maximum anchor-breadth is 9-14 ,u. The end- breadth is equal to the maximum breadth or slightly smaller, sometimes as much as 4 yu. The proportion of anchor-length to anchor-breadth is 100 to 53-72, on an average 100 : 62. The individual teeth, which arise vertically from the shaft, are strongly bent in their basal part and only slightly bent or nearly straight in their distal part, so that their tips are nearly parallel or slightly convergent. The small micramphidiscs (Plate 106, figs. 13-25) are 13.5-36 m long. Their length frequency-curve is rather broad and irregular. It exhibits two equally high main summits at about 18.4 and 22.1 yu, and one insignificant summit at about 27 yU. The shaft of these amphidiscs is straight, cylindrical, 0.8-1. 2 ^ thick, rough or smooth, and usually centrotyle. The tyle, which exceeds the adjacent parts of the shaft 0.2-1 ,u in transverse diameter, is often a good distance away from the middle of the length of the spicule. The terminal anchors are 3.5-14 yu in length, a fifth to a third of the whole spicule, and 5-9 m broad. The proportion of anchor-length to anchor-breadth is 100 to 61-162, on an average 100 : 119.4. The largest of these small micram- phidiscs, that is those over 30 m in length, are transitional to the large ones above described, not only in respect to size, but also in respect to anchor-shape. The proportion of anchor-length to anchor-breadth is in these spicules on an average 100 : 65. In all the small micramphidiscs, that, is in those under 30 n in length, the anchors are broader than long, the average proportion of anchor-length to anchor-breadth being in these spicules 100 : 125.6. The anchor-teeth of these spicules are generally strongly and rather abruptly bent at a point a third of their length from the base, and only slightly curved 284 HYALONEMA (PRIONEMA) PINULIFUSUM. in their distal and proximal portions. A more or less conspicuous conical spine with a maximum height of 0.5 n arises from the centre of the apex of the anchor. The anchors are very frequently irregular in so far as some teeth are considerably longer than the opposite teeth (Plate 106, figs. 21-23, 25). The nearest ally to H. (P.) crassum is H. (P.) spinosum (p. 273). From this H. (P.) crassum differs chiefly: — by possessing macramphidiscs with short and broad anchors and smooth teeth ; by the anchors of the serrated macramphidiscs being somewhat differently shaped ; by the absence of the spicules there described as small macramphidiscs ; by the largest micramphidiscs attaining a much larger size; by the presence of stout paratangential rhabds (tignules) in the superficial membranes ; and by having longer pinules. Hyalonema (Prionema) pinulifusum, sp. nov. Plate 70, figs. 11-24; Plate 71, figs. 1-11; Plate 72, figs. 1-15. I establish this species for a fragment trawled off the south coast of western Panama at Station 4621 on 21 October, 1904; 6° 36' N., 81° 44' W. ; depth 1067 m. (581 f.) ; it grew on a bottom of green mud and rock; the bottom-temperature was 40.5°. It possesses large pinules with distal rays greatly thickened in the middle and markedly fusiform in shape. To these the name refers. Shape and size. The specimen is a flat fragment, 14 cm. long, 8 cm. broad, and with a maximum thickness of 1 cm. The margin is lacerated. The speci- men is composed of lamellae about 1 mm. thick, separated by wide cavities. It probably formed part of a lamellar or cup-shaped sponge. The colour in spirit is brown. The skeleton. On many parts of the surface the pinule-fur is still more or less intact. A number of small wart-like protuberances, 0.5-1. 5 mm. broad and high, arise on one side of the lamellar body. These bear on their summits dense masses of medium-sized pinules. Much larger scattered pinules with stout, spindle-shaped distal ray arise from the walls of the wide depressions be- tween these protuberances. Pinules of the same kind densely cover the margins of some of the lamellae on the other side of the sponge. Other parts of the thin lamellae bear sparse, small pinules, with relatively few and small spines on the slender distal ray. Besides these three kinds of pinules, a fourth kind, with distal rays terminating in a rather long and slender terminal cone and with large second- ary spinelets on the primary spines of the distal ray, has been found quite frequently in the preparations. These pinules are identical with certain pinules HYALONEMA (PRIONEMA) PINULIFUSUM. 285 of Hyalonema ( Prionema ) azuerone, a large specimen of which was contained in the same bottle as the fragment of Hyalonema ( Prionema ) pinulifusum. I am therefore inclined to consider these pinules as spicules of the H. ( P .) azuerone which got into the H. (P.) pinulifusum accidentally. Of the three kinds of pinules which I consider proper to the sponge, the small ones with short and sparse spines on the distal ray are doubtlessly canalar. The two other kinds are probably dermal and gastral, but the fragmentary condition of the specimen renders it impossible to say which are which. In the follow- ing description I name these three kinds of pinules : — large pinules ; medium pinules; and small, canalar pinules, respectively. Pentactines have been found under various parts of the surface of the lamellae. Some hexactine and tylostyle megascleres and dense masses of diac- tine rhabds occur in the interior. The microscleres are numerous microhexac- tines, few micropentactines transitional between the microhexactines and the small canalar pinules, and amphidiscs. Of the latter seven kinds can be dis- tinguished : — macramphidiscs ; large and small mesamphidiscs with serrated teeth; large and small mesamphidiscs with smooth teeth; and large short- anchored, and small long-anchored micramphidiscs. The large pinules (Plate 70, figs. 15-19; Plate 71, fig. 11) are generally pent- actine, only very few hexactine ones having been observed. The distal ray is straight, fusiform, 200-400 /x long, generally 230-370 m, on an average 358 m, and 8-16 m thick at the base. Above it thickens very considerably and it measures, without the spines, 18-50 ^ in transverse diameter at the point of maximum thickness, which lies a short distance above the middle of its length. Farther on it again becomes thinner, and it ends in a rather broad and short, blunt- or sharp-pointed terminal cone. Its profile without the spines is elongate oval, drawn out at one end to the nearly cylindrical basal part and at the other to the terminal cone. The nearly cylindrical basal part and the distal cone are quite smooth, the remaining parts of it are covered with numerous large spines. The spines are usually all directed upwards and slightly curved, concave to the ray. The very lowest are quite divergent, the others strongly inclined, and in their end-parts nearly parallel to the adjacent part of the surface of the ray. Exceptionally (Plate 70, fig. 19) some of the lowest spines are directed down- wards. The spines are generally 12-40 m long, 3-8 m thick at the base, simple, conical, and sharp-pointed ; they rarely bear one or two secondary spinelets on the outer, convex side. The maximum diameter of the distal ray, together with the spines, is 40-63 ^ . 2S6 HYALONEMA (PRIONEMA) PINULIFUSUM. The lateral rays are straight, in the same spicule equal or somewhat unequal, and either nearly cylindrical throughout and terminally rounded, or cylindrical in their proximal part, conical in their distal part, and blunt-pointed. They generally bear a small number of rather larger spines on their distal part. The lateral rays are, at the base, considerably thinner than the basal part of the distal ray, and attain a length of 34-52 n, on an average 44.5 yu. The proximal ray of the hexactine forms is about as long as the laterals. The medium pinules (Plate 70, figs. 20-24) are pentactine. Their distal ray is straight, 165-216 n long, generally 167-205 n, on an average 189 yu, and 5.5-9 m thick at the base. Their basal part is for a considerable distance free from spines, and they end in a very short likewise spineless terminal cone. Their remaining parts bear somewhat sparse and rather divergent spines which are slightly curved, concave to the ray. The spines are conical, sharp-pointed, about 3 m thick at the base, and attain 30 n in length. They are usually simple; occasionally one or two bear a small secondary spinelet. The maximum thick- ness of the distal ray, together with the spines, is 33-48 n. The lateral rays are conical, terminally rounded, and 35-48 m long. Their distal part bears a small number of rather large spines which sometimes form an irregular verticil below the end of the ray. The small canalar pinules (Plate 70, figs. 11-14) are generally pentactine, very rarely hexactine. The distal ray is 110-240 n long, generally 120-206 /x, on an average 167 n, and 3. 5-8.3 fx thick at the base. Its basal part and its long and slender terminal cone are smooth; its middle-part bears a small number, generally about a dozen or so, of sparse, small, straight or slightly curved spines which are directed obliquely upwardly. The maximum thickness of the distal ray, together with the spines, is 9-25 yu. The lateral rays are cylindrical and smooth in their basal, conical and spiny in their distal part. They measure 28-62 ij. in length. The proximal ray (of the hexactine forms) is about as long as the laterals. The superficial (hypodermal and hypogastral) pentactines have straight, conical, terminally rounded rays. The dimensions of the few I was able to measure are: - — basal thickness of rays 10-23 , u, length of proximal ray 300-410 yu, length of lateral rays 177-430 yu. The hexactine megascleres observed were 0.6-1 mm. in diameter, and had straight conical rays, 10-24 ix thick at the base. Most of the rhabd megascleres are rather long blunt amphioxes with hardly a trace of a central tyle. Besides these spicules, which form the bulk of the HYALONEMA (PRIONEMA) PINULTFUSUM. 287 supporting skeleton, smaller amphioxes with distinct central tyle, tylostyles, and, exceptionally, amphityles are met. The ordinary amphioxes are fusiform, very blunt at the ends, 0.8-2. 5 mm. long, 10-33 fi thick in their middle-part, and generally curved. In a good many of them, particularly the long ones, the curvature is very considerable. A few angularly bent spicules of this kind have also been observed. The small centrotyle amphioxes are generally 390-620 m long; but larger ones, connecting them with the amphioxes above described, have also been observed. The small centrotyle amphioxes are straight or only slightly curved, and 7-14 n thick near the middle. The central tyle is 12-30 /x in transverse diameter, that is 5-16 m more than the adjacent parts of the spicule. The tylostyles are amphiox-derivates with one ray reduced in length and terminally thickened. Their dimensions are: — total length 1.2-1. 7 mm.; maximum thickness 16-22 n at morphological centre, which lies somewhere between the middle of the length and the terminal tyle; transverse diameter of terminal tyle 13-24 /x; thickness just below terminal tyle 10-16 m, that is 3-8 n less than the diameter of the terminal tyle. The terminal tyle is more or less spherical, and usually bears one or two small, stout, truncate or terminally rounded spines. Occasionally a rather large spine arises from it. The amphityles are amphiox-derivates with both rays reduced in length and terminally thickened. One that I measured is 1.7 mm. long, and 27 n thick in the middle and just below one of the terminal tyles. Towards the other tyle it is attenuated to 15 n. The two terminal tyles are respectively 41 and 22 n in diameter. The microhexactines (Plate 71, figs. 1-4, 9) are regular, the six rays of the same spicule usually being fairly equal. These spicules measure 80-120 m in total diameter. The rays are straight or slightly curved, conical, fine-pointed, 1.5-2. 2 \x thick at the base, and just perceptibly roughened by exceedingly minute spines. A few micropentactines (Plate 71, fig. 10) have been found, which appear to connect the regular microhexactines with the small canalar pinules. These spicules are 80-140 /x in diameter and have rays 2-3.7 m thick at the base. The ainphidiscs, which are 15-470 n long, exhibit a remarkable degree of diversity. I have measured 178 of them. Their length frequencies are repre- sented in Figure 14. The figure shows that the lengths of the amphidiscs form a nearly uninter- rupted series. At one point only we find the next largest amphidisc more than 288 HYALONEMA (PRIONEMA) PINULIFUSUM. V— * ►— ‘H- * Mr-* » O H-4 tO CO G> ^ 00 ^OO h-»tO CO 4^ CH Length 13.11 — 14.42 — 15.86 — 17.45 — 19.19 — 21.11 — 23.23 — 25.55 — 28.10 — 30.91 — 34.00 — 37.40 — 41.14 — 45.26 — 49.78 — 54.76 — 60.24 — 66.26 — 72.89 — 80.18 — 88.20 — 97.02 — 106.72 — 117.39 — 129.13 — 142.04 — 156.25 — 171.87 — 189.06 — 207.97 — 228.76 — 251.64 — 276.81 — 304.49 — 334.93 — 368.43 — 405.27 — 445.80 — 490.38 — 539.41 — ST v> ©.o cr i-k w n a> cl --fr_r -v-A.-ji --T;> -H — * u iia diameter. I am inclined to consider these spicules as rnonac- tine-derivat.es of the slender-rayed long-spined basal tri- to hexactines above described. The angularly bent centrotyle diactine acanthophores are also very rare. They have a spiny tyle and two straight, rays enclosing an angle of about 90°. In one of these spicules measured, the two actines were quite straight, and respectively 13 m thick and 430 and 500 u long. The spiny central tyle was 28 /x in diameter. The stout, straight or slightly curved, centrotyle diactine acanthophores (Plate 63, figs. 20-23) are usually 550-920 u long, and 14-30 m thick near the centre. The central tyle is 20-54 \± in diameter. The proportion of the thickness of the tyle to the thickness of the adjacent, parts of the spicule is 114-300 : 100. When the tyle is large, it is spiny (Plate 63, fig. 20); when it is small, it is smooth (Plate 63, figs. 21-23). The two rays of these spicules have the same shape as the rays of the tri- to pentactine stout-rayed basals above described, but are on the whole longer. I think there can be no doubt, about these spicules being diactine-derivates of the stout-rayed tri- to pentactine acanthophores. HYALONEMA (PRIONEMA) FIMBRIATUM. 299 The stout, strongly curved , not centrotyle rhabd acanthophores (Plate 63, figs. 27, 28) are rare. They are cylindrical, thickened at both ends, and uni- formly or irregularly curved. Their middle-part is smooth; their thickened ends are spiny. These spicules are, measured along the chord connecting their ends, usually 300-400 fx long, and about 18 n thick. The terminal thickenings (tyles) are spherical and measure 35-50 n in diameter. The slender rhabd acanthophores (Plate 63, fig. 24) are usually slightly and uniformly curved, 0.9-1. 3 mm. long, and 5-15 m thick near the middle. Their ends are more or less spiny and usually thickened. The terminal thickening is sometimes 25 m and more in transverse diameter. A central tyle, 2-4 n thicker than the adjacent parts of the spicule, is usually present. The strongly curved, slender rhabd acanthophores (Plate 63, figs. 25, 26) are rare. They are destitute of a central tyle and appear as strongly and irregularly curved slender rods about 7 /x thick. They are usually thicker at one end than at the other, and thickened at both ends to unequal terminal tyles which are spined, more or less spherical, and have a maximum transverse diameter of 25 m- The maximum diameter (length) of the curve formed by these spicules is usually 300-500 /x. The basal anchor-spicules (Plate 62, figs. 5-11) are spined rods with an anchor at the distal end. These rods have near the middle a maximum thickness of 72 n, and are attenuated both proximally and distally; proximally to a fine point, distally to a thickness of 9-32 n just above the anchor. The distal and middle-parts of these rods are covered with straight, strongly inclined, inwardly directed spines 10-25 m long. Proximally these spines become smaller and finally disappear, so that the inner end-part of the spicule appears quite smooth. The rod is traversed by an axial thread which terminates distally in the middle of the anchor. The end is thickened, and from this thickening four short branch- threads arise, which form a cross lying in a plane vertical to the rod or anchor-shaft. The terminal anchor is 22-128 m high and 43-140 ^ broach It consists of a stout, spherical centrum from which a number of anchor-teeth arise. The centrum appears as a terminal tyle of the rod forming the anchor-shaft. The teeth extend at various angles obliquely backward (upward) and outward. They are sometimes 40 m long, blunt, and very irregular and variable in position, shape, curvature, and size. Some are bifurcate or otherwise branched. All the anchors observed lay altogether within the sponge. The stalk, which no doubt Was present in life, is absent in all the specimens. Probably anchors of the kind described above take part in its formation. A few smooth 300 HYALQNEMA (PRIONEMA) FIMBRIATUM. and very stout spicule-fragments found within the stalk-protuberance make it probable, however, that either these anchors are not the sole stalk-spicules, or that the proximal, smooth end-parts of the anchor-shafts are very greatly increased in length and in thickness during the process of further growth, which leads to their distal parts being pushed out from the body to form the protruding stalk. The six rays of the microhexactines (Plate 60, figs. 25-30; Plate 62, figs. 42-45) are usually fairly equal; more rarely two opposite ones exceed the other four markedly in length. The microhexactines with equal rays measure 56-95 n in total diameter, most frequently 65-85 n, on an average (of 44 measurements) 75.3 n. Their rays are 1.8-2. 8 n thick at the base, usually about 2 m, conic, and attenuated to fine points at the end. They bear rather sparse, minute spines. The spines of the basal and middle-parts of the ray are usually 0.2-0. 5 n long; distally they become smaller. The basal half or so of the ray is quite straight, the distal part curved. Where the straight basal part passes into the curved distal part an abrupt, sometimes quite angular bend is often discernible. The curvature of the distal part is very considerable, the direction of the end-part diverging up to 120° and more from the direction of the basal part. The direc- tion of curvature of opposite rays is usually opposite, so that any two opposite rays together generally form an S-shaped curve. The rare microhexactines with two opposite rays exceeding the other four in length measured were 80-90 n long and 40-50 n broad. In these spicules the two opposite, longer rays are not so strongly curved as the four shorter ones. In a spicule-preparation I found a monactine microhexactine-derivate which appeared as a minutely spined tylostyle with strongly bent pointed end. Its measurements were: — chord 57 n] thickness 2.5 n', tyle 4.5 n. A few microhexactines 110-120 ^ in diameter with straight rays, 4-5 m thick at the base, were also observed. These rare spicules were perhaps foreign. The micro pentactines (Plate 60, figs. 31-34; Plate 62, fig. 28) consist of one slightly longer apical and four shorter lateral rays, which latter are fairly equal in size and extend in a plane vertical to the apical ray. The rays of these spicules are straight in their proximal and curved, generally very considerably, in their distal part. Opposite lateral rays are curved either in the same or in different directions. The rays are, measured along the chord, 35-79 ju long, conic, pointed, and 2. 8-3. 7 m thick at the base. They bear conic, pointed spines, which, in the proximal part of the ray, attain a length of 0.7 fx. Distally the spines become smaller. These spicules are connected by transitional forms with the canalar pinules. HYALONEMA (PRIONEMA) FIMBRIATUM. 301 Occasionally smaller micropentactines with straight rays are met. In a spicule of this kind the rays measured were 4 n thick at the base, the apical ray was 54 n long; the laterals were 34 n long. Of amphidiscs several kinds can be distinguished: — A, large ones, with medium anchors the teeth of which are smooth, and have straight or outwardly curved, diverging ends; B, large, medium-sized, and small ones with slender anchors, the teeth of which bear frill-like, fimbriate membranes on their margins and have inwardly curved, convergent ends; and C, small ones with broad anchors, the teeth of which appear smooth and have end-parts more or less parallel to the shaft. I measured 202 amphidiscs. The frequency of the various lengths is repre- sented in the following exponential graph (Fig. 15). 302 HYALONEMA (1*R ION EM A) FIMBRIATUM. The part of the curve between 304.49 and 490.38 n pertains to the large amphidiscs with smooth, divergent anchor-teeth, A; the part between 34.00 and 334.93 fi to the amphidiscs with fimbriate, convergent anchor-teeth, B; and the part between 14.42 and 41.14 n to the amphidiscs with smooth anchor-teeth with parallel end-parts, C. There is no dimensional overlapping of A and B and only a slight overlapping of B and C, 14.42 and 34.00. The dimensionally transitional forms of B and C causing this overlapping are, however, rare, so that the part of the curve between 14.42 and 34.00 pertaining to them lies quite low. The three differently shaped amphidisc-forms (A, B, and C) are differentiated accord- ingly not only in regard to their shape but also in regard to their size (length). Fig. 15 further very clearly shows that the amphidiscs A and C vary only slightly in size and form biometrically homogeneous groups, and that the amphidisc B has a very wide range of dimensional variation and does not form a biometrically homogeneous group. The part of the frequency-curve f pertaining to this group exhibits one high and rather broad and three smaller elevations. This shows that the main-group B consists of four secondary groups, the amphidiscs belonging to one of which are frequent, those belonging to the three others, rare. It is therefore advisable to distinguish six groups (three main-groups, one of which, B, comprises four secondary groups) of amphidiscs in the sponges here described: — A, macramphidiscs, Ba, largest fimbriate amphidiscs, Bb, large fimbriate amphidiscs, Be, small fimbriate amphidiscs, Bd, smallest fimbriate amphidiscs, and C, micramphidiscs. The macramphidiscs (Plate 59, figs. 1-6; Plate 62, fig. 31) are 335-446 n long, most frequently about 400 fi. The shaft is cylindrical, straight, 8-16 n thick, most frequently about 12 n, and abruptly thickened in or near the middle to a central tyle 11-22 /j. in transverse diameter. The proportion of the thickness of the adjacent parts of the shaft to the thickness of the tyle is 100 to 121-167. From the tyle a verticillate bunch of spines arises. The number of the spines forming this bunch is variable. Sometimes they are few in number and small in size (Plate 59, fig. 2), sometimes numerous and large (Plate 59, fig. 1). Forms intermediate between these extremes are the most frequent. The spines form- ing these bunches are irregularly distributed and, when few in number, fre- quently confined to one side of the shaft. The individual spines are 7-26 n long, 4-5.5 m thick at the base, cylindrical throughout and terminally rounded, or attenuated distally, truncate, and provided with a cluster of exceedingly minute secondary spinelets on the terminal face. The primary spines arise vertically or steeply from the central thickening of the shaft and are, farther on, HYALONEMA (PRIONEMA) FIMBRIATUM.' 303 curved, usually all more or less in the same direction. In short spines this curvature is insignificant, in long spines, very pronounced. The long spines are usually strongly curved in their basal part and straight or slightly curved, not infrequently in the opposite direction, in their distal part. The plane of the main curvature either passes through the axis of the shaft, or it is oblique to it. Since, as above stated, all the spines on the tyle are usually curved in the same direction, the verticillate bunch formed by them appears — when the spines are long — bent, straight or spirally, toward one end of the spicule. The remain- ing parts of the shaft are smooth. The axial thread passes through the central tyle without being thickened, and there is no trace of an axial cross. I noted, however, a few small dots in the central part of the tyle, near the axial thread, which appeared to have the same refractive index as the axial thread. The two anchors of the same spicule are fairly equal, or rather unequal, in size. The anchors are 80-180 n long, a third to two fifths of the whole spicule, and 70-113 m broad. The proportion of anchor-length to anchor-breadth is 100 to 46-84, usually 100 to 63-80, on an average (of sixteen calculated individual proportions) 100 : 70. The individual anchor-teeth are near the base 10-14 m high, and a little farther out, at their widest point, 12-22 ^ broad. They are attenuated distally and at the end simply rounded (Plate 59, figs. 5, 6; Plate 62, fig. 31) or, more rarely, divided, by a slight indenture, into two terminal lobes (Plate 59, fig. 4). They arise steeply or vertically from the end of the shaft and are curved in their basal part through an angle of about 80°. Then they become nearly or quite straight and remain so to within a short distance of the end. This long straight part of the tooth encloses an angle of about 10° with the continuation of the axis of the shaft. The end-part of the tooth is slightly bent outward or more rarely straight and extended in the same direction as the middle-part. The plane of the normal curvature of the tooth passes through the axis of the shaft. Occa- sionally the end-part of a tooth is bent also in a plane vertical to this, paratan- gentially as it were, to one side (Plate 59, fig. 6). The fimbriate a?7iphidiscs are all very similar. The only differences between the four biometric groups of them, that is the largest, large, small, and smallest, are those due to the relative anchor-breadth decreasing and the relative size of the central tyle of the shaft increasing with the size of the spicule. Their anch- ors are from a little less than two fifths to nearly half the whole spicule in length. The largest fimbriate amphidiscs (Plate 60, figs. 1-6, 24; Plate 61, figs. 1-11; 304 HYALONEMA (PRIONEMA) FIMBRIATUM. Plate 62, fig. 27) form a biometrically homogeneous and well-defined group, entirely separated dimensionally from the (larger) macramphidiscs on the one hand and the (smaller) large fimbriate amphidiscs on the other. The largest fimbriated amphidiscs are 200-323 n long, most frequently about 250 n long. The shaft is straight, on the whole cylindrical, and 4-7.5 n thick. Its thickness is fairly proportional to the length of the spicule. The shaft is thickened slightly and gradually towards the ends, and considerably and abruptly somewhere in its middle-part. The latter thickening, the central tyle, is usually some distance, occasionally (Plate 60, fig. 5) very far away from the real (geometrical) centre of the shaft, and measures 8-14 n in transverse diameter. The proportion between the thickness of the adjacent parts of the shaft to the thickness of the tyle is 100 to 160-325. From the central tyle a verticillate bunch of spines arises. These spines (Plate 62, fig. 27) are 5-15 m long, at the base 2-2.8 n thick, cylindrical, and terminally simply rounded, or attenuated distally and truncate with a cluster of exceedingly minute secondary spinelets on the terminal face. The (primary) spines are curved. The curva- ture is irregular, and a rather abrupt angular bend usually occurs somewhere near the middle of the length of the spine. Generally all the spines of the bunch are, as in the macramphidiscs, curved in the same direction longitudinally or obliquely (spirally). The parts of the shaft outside the central tyle bear very numerous spines, the largest of which are 1 n long, 1.5 ^ broad, cylindrical, and provided with a cluster of exceedingly minute secondary spinelets on their flat or rounded terminal face (Plate 60, figs. 5, 6; Plate 62, fig. 27). The degree of development of these scattered (primary) spines is very variable ; often they are reduced to hardly perceptible protuberances on the surface of the shaft (Plate 60, fig. 3). The two anchors of the same spicule are fairly equal, or rather unequal, in size. They usually consist of eight teeth. The anchors are 72-136 n long, and 43-67 m broad at their broadest point and attenuated distally, their ends meas- uring only 32-60 n in transverse diameter. The difference between the maxi- mum and end-breadth of the anchors is 3-18, on an average (of 29 measure- ments) 7.8 fi. The proportion of the length to the maximum breadth of the anchors is 100 to 42-72, on an average (of 29 calculated proportions) 100 : 52.2. The largest (longest) anchors are on the whole narrower than the smaller (shorter) ones. The average proportion of length to maximum breadth is in the anchors over 120 n in length 100 : 47.8, in those under 100 n in length 100 : 55.7. The individual anchor-teeth arise nearly vertically from the end of the HYALONEMA (PRIONEMA) FIMBRIATUM. 305 shaft, are strongly curved, concave to the shaft, for a short distance quite at the base, and slightly and quite uniformly curved in the same direction for the remainder of their length. The total curvature is such that the ends of the teeth converge towards the shaft, and enclose with it angles of about 8°-16°. The body of the tooth has the usual T-shaped transverse section. The lower (radial) part increases in height proximally to 5-9 n. The upper (paratangen- tial) part is 6-10 ^ broad near the middle of the length of the tooth and attenu- ated both proximally and distally. The distal end of the body of the tooth is narrow and blunt-pointed. The two margins of the outer part of the tooth (which corresponds to the horizontal upper stroke of the T) are continued in fine, frill-like, fimbriate, siliceous membranes, which diverge from the plane through tooth- and shaft- axis and extend obliquely inward. The tooth, together with its two fimbriate marginal membranes, has a transverse section (Fig. 16). Upper (paratangential) part of the tooth. i i i Marginal fimbriate membrane. i i i i i i Lower (radial) part of the tooth. Fig. 16. — Anchor-tooth. Section. The fimbriate marginal membranes extend from the base (Plate 61, figs. 4, 5, 8, 9) to the tip (Plate 61, figs. 6, 7, 10) of the tooth and even slightly beyond it. They are at the base of the tooth quite narrow, only about 1 m broad (Plate 61, figs. 4, 5, 8, 9) ; in the middle of the tooth (Plate 61, figs. 1-3) they broaden distally and attain a breadth of about 7 n. Beyond they again become slightly narrower and are, at the end of the tooth, about 4 m broad. Narrow and deep incisions, extending down to the body of the tooth, divide these membranes into lobes, which are, in the distal and middle-part of the tooth, on an average about 306 HYALONEMA (PRIONEMA) FIMBRIATUM. 2 /d broad; proximally they become considerably narrower. Secondary inci- sions subdivide the marginal parts of these primary into secondary lobes, so that they attain a somewhat dendritic appearance (Plate 61, figs. 1-3). I am not aware that such fimbriate marginal membranes have hitherto been observed in the amphidiscs of the Hexactinellida Amphidiscophora. They may be compared with the thin marginal parts of the cladomes of the phyllo- and discotriaenes of certain lithistid Tetraxonida. The large fimbriate amphidiscs (Plate 60, figs. 7-11) are 122-185 n long, most frequently about 163 m- Their shafts are 2-4 m thick. Their thickness is fairly proportional to the length of the spicule. The central tyle is 3-7 /x in diameter, two thirds to twice as thick as the adjacent parts of the shaft. The spines arising from the tyle are similar to those of the largest fimbriate amphidiscs but proportionately smaller and usually not all curved in the same direction (Plate 60, figs. 8, 10). The remainder of the shaft usually is more spiny than in the largest fimbriate amphidiscs. The anchors are 39-80 m long; their maximum breadth is 26-55, their end-breadth 20-50 The difference between maximum and end-breadth is 3-6 n, on an average (of ten measure- ments) 5.2 n. The proportion of the length to the maximum breadth of the anchors is 100 to 50-73, on an average (of ten calculated proportions) 100 : 58.8. A correlation between amphidisc-length and relative anchor-breadth is not discernible in the amphidiscs belonging to this subgroup. The small fimbriate amphidiscs (Plate 60, figs. 12-14) are 64-99 m long, most frequently about 77 m- The shaft is 1.5-1. 8 n, the central tyle usually 2-3 m thick. Strongly bent spines usually arise from the latter. Smaller short and broad spines cover the remaining parts of the shaft quite densely. The anchors are 23-36 m long and have a maximum breadth of 13-21 /x. The end- breadth is usually 1-2 /j. less than the maximum breadth. The proportion of length to maximum breadth of the anchors is 100 to 52-72, on an average (of six calculated proportions) 100 : 59. The smallest fimbriate amphidiscs (Plate 60, fig. 15; Plate 62, fig. 15) are 36-54 m long, most frequently about 52 and 38 /x long. The shaft is 1.2-1. 8 /x thick. A central thickening, as much as 2.8 ^ in diameter, is sometimes dis- cernible. Often, however, there is hardly any trace of such a tyle. The shaft is covered with spines about 0.5 m long. The anchors are 16-24 long, and have a maximum breadth of 9.5-13 /x. The end-breadth is 1-2 n less than the maximum breadth. The proportion of the length to the maximum breadth of the anchors is 100 to 55-75, on an average (of eight calculated proportions) 100 : 63.1. OONEMA. 307 The micramphidiscs (Plate 60, figs. 16-23; Plate 62, figs. 12-14) are 15-40 n long, most frequently about 20 n. The shaft is cylindrical, straight or, very rarely, slightly curved, and 0.7-1. 7 n thick. Sometimes it is slightly and gradu- ally thickened near the middle up to 2 ; more frequently no trace of a central thickening can be detected. The shaft is covered by blunt or truncate spines about 0.5 n long. These spines are often very numerous. The anchors are 4-14 n long, usually a little less than a third of the whole spicule, and 5-12.5 m broad. The proportion of their length to their breadth is usually 100 to 68- 130, rarely up to 100 : 156, on an average (of thirty calculated proportions) 100 : 111.5. The larger micramphidiscs have relatively narrower (more slender) anchors than the smaller. In the micramphidiscs with anchors under 7.5 m in length the proportion of anchor-length to anchor-breadth is generally 100 to 100-130, rarely up to 100 : 156, on an average 100 : 118.9. In the micramphi- discs with anchors over 7.5 m in length this proportion is 100 : 68-114, on an average 100 : 86.6. In consequence of the slenderness of their anchors the larger micramphidiscs appear as transitional forms connecting the smaller micramphidiscs with the smallest fimbriate amphidiscs. The individual anchor- teeth of the micramphidiscs are uniformly and considerably curved, concave to the shaft, in their basal part. Distally this curvature decreases and their end-parts are nearly straight. The total curvature is such that the (nearly straight) end-part of the teeth come to lie parallel or nearly parallel to the shaft and to each other. The above sponges differ from all the species of Hyalonematidae hitherto described by the anchor-teeth of their fimbriate amphidiscs bearing marginal frills. In some respects, particularly in respect to the basal anchors and the microhexactines, they resemble Hyalonema depressum F. E. Schulze. In respect to other characters, particularly in the various kinds of amphidiscs, they differ, however, fundamentally also from this sponge. OONEMA, eubgen. nov. Species of Hyalonema of which the amphidiscs of one of the kinds have relatively very large and broad, usually more or less semispherical, anchors about half of the whole spicule in length. The collection contains six specimens of this subgenus, which belong to five species, four of which are new. 308 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. Hyalonema (Oonema) bianchoratum pinulina, var. nov. Plate 82, figs. 1-34; Plate 83, figs. 1-68; Plate 84, figs. 1-32; Plate 85, figs. 1-8. Two fine specimens of this variety were trawled off the coast of northern Peru at Station 4651 on 11 November, 1904; 5° 41.7' S., 82° 59.7' W. ; depth 4063 m. (2222 f.); they grew on a bottom of sticky, fine, gray mud; the bottom- temperature was 35.4°. In the following description one of them is designated a, the other b. With other characteristics these sponges differ from the typical Hyalonema {Oonema) bianchoratum Wilson by the distal rays of their pinules attaining not nearly so great a length. To this the name of the variety refers. Shape and size. Both specimens are upright, cylindrical, widened above to form a shallow cup, and rounded at the lower end, from which a rather eccen- trically situated stalk arises. From the bottom of the cup a cylindroconical terminally rounded gastral cone protrudes. Specimen a is 111 mm. long, the longest and shortest diameters of its upper end being respectively 49 and 31 mm. Specimen b (Plate 82, fig. 1) is 141 mm. long. The longest and shortest transverse diameters of the central cylindrical part of its body are 49 and 42 mm., those of its upper, cup-shaped extension respectively 66 and 48 mm. The stalk of specimen a is broken off at a distance of 40 mm. from its point of origin, that of b close to the body of the sponge. An isolated stalk, in the same jar as the body of specimen b, which fits the stump at the lower end of the body, apparently belongs to it. This stalk, which was attached to the stump before the specimen was photographed (Plate 82, fig. 1), is 230 mm. long, and, near its point of origin, circular in transverse section, and 3.8 mm. in diameter. Surface. Pores could not be found where the choanosome extends up to the superficial membrane. These poreless tracts appear as broad bands which form a network with irregular meshes, the maximum diameter of which is rarely more than 1 mm. on the dermal face, but is sometimes as much as 10 mm. on the gastral face. In the meshes of this primary network are spread out reticular sieve- membranes (Plate 82, fig. 1; Plate 83, figs. 60-62) composed of narrow bands of superficial (dermal or gastral) tissue. The meshes of the dermal secondary reticulations are usually 100-300 m wide, those of the gastral usually 300-500 n. The nodes of these nets are much thickened. In the meshes of the dermal pore-sieves (Plate 83, fig. 62) some remnants of what seems to have been a ter- tiary network were observed. In the meshes of the gastral pore-sieves (Plate 83, fig. 61) no such remnants could be found. HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 309 Canal-system. The pores of the dermal sieves on the outer side of the body lead into wide canals extending into the interior. Other still wider canals extend up to the gastral sieves on the inner face of the cup. Between these wide canals, the former of which are, no doubt, afferents and the latter efferents, a tissue is found containing narrow canals, and rather densely packed small flagellate chambers (Plate 84, fig. 2). The sections of these flagellate chambers (Plate 84, fig. 2a) are mostly circular or broad-oval and 50-120 ^ in maximum diameter. The colour of both specimens in spirit is greenish brown. The skeleton. The poreless parts of the surface and the strands forming the pore-sieve nets are, both on the dermal and the gastral face, covered by a dense pinule-fur (Plate 83, figs. 45b, 61, 62). Under the poreless tracts of both faces paratangential, more or less centrotyle amphioxes and the lateral rays of pentactine megascleres form a superficial (hypodermal, hypogastral) skeleton. The strands of the dermal pore-sieve nets are supported by the lateral rays of hypodermal pentactines and a few centrotyle amphioxes (Plate 83, fig. 62). The centra of the pentactines are here usually about 700 n apart. In the gastral pore-sieve nets no pentactines have been found. Here centrotyle amphioxes, congregated in dense bundles, alone occupy and support the strands of the reticulation (Plate 83, fig. 61). Numerous centrotyle amphioxes, rather scarce hexactine megascleres, and masses of microhexactines occur in the choanosome. Some of the niicro- hexact.ines have straight, others curved rays. I think it not improbable that the former, which are much the scarcer, line the walls of the wide main canals, and are to be considered as canalaria; while the latter are imbedded in the choanosomal tissue, and are to be considered as parenchymalia. Four kinds of amphidiscs can be distinguished: — large and small macram- phidiscs, and large and small micramphidiscs. The large macramphidiscs are rather scarce in both specimens and confined to the choanosome, where they appear to be irregularly scattered. The small macramphidiscs are very numer- ous on and in the gastral membrane of specimen a, where most of those seen in situ in the sections were found to lie between the distal rays of the pinules wholly outside the sponge, with their shafts vertical to the surface (Plate 83, fig. 45c), while only a few are scattered irregularly in the gastral membrane. On the dermal face of this specimen small macramphidiscs have also been observed, but they are here not nearly so numerous. In specimen b these amphi- discs are similarly situated but much less abundant. The large micramphidiscs are very rare in both specimens, the small very numerous in b, but somewhat 310 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. scarce in a. I observed a large number of these small micramphidiscs in situ in the gastral membrane of specimen b, where they lie in large part paratangen- tially with their shafts parallel to the surface; and I found a great many also in the centrifuge spicule-preparations of specimen b, both in this membrane and in the choanosome. One- to six-rayed acanthophores with terminally or, much more rarely, entirely spined rays are abundant in both specimens in the vicinity of the point of origin of the stalk. In specimen a these spicules are on the whole stouter than in specimen b. The skeleton of the stalk extends through the body of the sponge up to the gastral cone. Its upper, imbedded part consists of centrostyle amphioxes and the upper end-parts of the large spicules forming the free part. The latter, provided it really belongs to the sponge, is in specimen b (Plate 82, fig. 1) composed of five stout and about a dozen more slender spicules twisted spirally together. The free part of the stalk of specimen b is composed of about a dozen stout and a small number of slender spicules. The symbiotic zoantharian polyps. To the proximal end-part of the stalk of specimen a is attached a tubular Palythoa colony, enclosing the stalk like a tight-fitting mantle for a distance of 17 mm. The individual polyps arising from this tubular colony are about 3 mm. high and 4 mm. broad. Polyps and coenenchym are provided with a stout skeleton composed entirely of acan- thophores of the sponge, to the stalk of which the colony is attached (Plate 84, fig. 1). In the polyps longer and more slender spicules lying radially in the radii of the septa occupy the oral plate, and perhaps also the upper parts of the septa. In the superficial parts of the lateral walls of the polyps and the coenenchym shorter, stouter, and on the whole more spiny spicules, lying close together, form a dense cortex. Still shorter, stouter, and more spiny spicules are found near the axis around the mouth and in the wall of the stomatodeal funnel. On the stalk which probably belonged to specimen b no polyps were observed. Its proximal end-part is, however, enveloped by a thin mantle (Plate 82, fig. 1) brown in colour, chitinous in nature, and entirely destitute of spicules; this mantle may be the basal part of the coenenchym of a zoantha- rian polyp-colony. In the body of specimen a no symbiotic polyps were observed; the dermal region of the body of b on the other hand contains a large number of such polyps (Plate 82, fig. 1; Plate 83, fig. 60a). These polyps (Plate 84, fig. 14) are Zoanthidae. They contain no spicules at all and are, in their present contracted state, nearly spherical, and 1.3-1. 8 mm. in diameter. HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 311 The polyps lie in excavations of the sponge-body just large enough for them. Their distal ends are flush with the surface of the sponge. In life, when expanded, they probably protruded more or less beyoryl its surface. These polyps form groups within which they are about 4.5 mm. apart (Plate 83, fig. 60). The coenenchym-like mantle enclosing the upper end of the stalk, which has been referred to above, may have formed part of a colony of polyps similar to those in the body of the sponge. Some of the polyps in the sponge-body which I examined bore a short thread-like protuberance on their lower (inner) end. Probably all the polyps of a group, possibly all the polyps of the whole sponge, are connected by such threads. I did not make sure of this, however, because for this purpose it would have been necessary to cut up the fine and unique specimen. The pinules (Plate 82, figs. 21-34; Plate 83, fig. 45b). The dermal pinules of the upper and middle-parts of the body in both specimens resemble, as radial sections show, the gastral pinules, but differ from the dermal pinules on the basal part of the sponge, the latter being larger and having distal rays with more divergent spines. In the spicule-preparations of different parts of the surface besides the pinules shown by the sections to be truly proper to the region in question, I always found a few others; in the spicule-preparations of the gastral membrane and the upper and middle-parts of the dermal membrane were typi- cally basal spicules; and in the spicule-preparations of the basal part of the dermal membrane were pinules of the type found in situ on the upper parts of the sponge. The principal dimensions of the pinules are tabulated on p. 312. The gastral pinules (Plate 82, figs. 29, 30; Plate 83, fig. 45b) and the dermal pinules on the upper and middle-parts of the spo?ige (Plate 82, figs. 22, 31-33) are nearly always pentactine, very rarely hexactine. Their distal ray is straight and 120-280 n 1 long. It ends with a terminal cone free from spines. Its proxi- mal part is also spineless, and it arises with a trumpet-shaped extension from the cross formed by the lateral rays. Farther up the distal ray becomes thinner, and it attains its minimum thickness at a distance of about 30 n from its base (the centrum of the spicule). Beyond that it again becomes thicker. At its thinnest point the smooth proximal part of the distal ray is 7-11 n thick. The basal thickening is variable. The distal ray of a typical upper dermal pinule is 17 jj. in diameter at its thickened base, 30 n higher up, and 11/^ at its thinnest point. The whole of the distal ray, with the exception of its proximal and distal 1 This and the following measurements refer to the pinules of both specimens together. 312 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. Pinules Length of distal ray M Thickness of the thin- nest part of the distal ray near its base ix limits Maximum thickness of the distal ray to- gether with the spines ii limits Length of the lateral rays M limits average limits average of specimen a gastral 165-265 219.5 9-10.5 20-26 35-53 43.1 dermal from the upper and middle- parts of the body 170-250 211.2 7-10 21-23 30-50 38.7 from the basal part of the body 130-330 234.5 9.17 30-65 40-80 56 of specimen b gastral 120-280 214.2 7.5-11 17-33 28-52 37.5 dermal from the upper and middle- parts of the body 180-266 217.9 8-10 20-26 32-60 40.1 from the basal part of the body 150-305 240.7 10-16 35-65 35-62 48.5 end-parts, bears rather strongly inclined spines, which are slightly curved, concave to the ray. These spines attain their largest size at, or some distance above, the middle of the ray. Here the distal ray, together with the spines, attains a maximum thickness of 17-33 p. The lateral rays of the same spicule are usually equal, 28-60 n long, straight, cylindroconical, abruptly and bluntly pointed. They are smooth in their proximal part, and in their distal part are covered with rather sparse broad spines, usually up to about 1 m long. Some- times one ray is reduced in length, nearly cylindrical, and terminally rounded. Of hexactine forms (with a proximal ray) I have found (and measured) six, four of which were found among the gastral pinules of specimen a. The proximal ray is conical, pointed, covered with spines in its distal part, and 10-40 n long. The basal dermal pinules (Plate 82, figs. 21, 23-28, 34) are, like those above described, nearly always pentactine, very rarely hexactine. Their distal ray is straight, 130-330 p long, and spineless in its proximal part. It ends in a likewise spineless terminal cone. In these pinules the smooth proximal part is HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 313 also somewhat hour-glass-shaped, and is at its thinnest point 9-17 /x thick. Its spines are usually quite strongly divergent, and markedly curved, concave towards the ray. They attain their greatest size one half to two thirds of the length of the distal ray from the centrum, or still higher up, and here the distal ray, together with the spines, attains a maximum thickness of 30-65 m- The lateral rays are similar to those of the pinules of the upper part of the sponge, above described, but stouter and provided with larger spines. They attain a length of 35-80 /x. Of hexactine forms I found (and measured) only two, with proximal rays 12 and 20 ^ long respectively. One of these is conical and pointed, the other (Plate 82, fig. 26) cylindrical and terminally rounded. The hypodermal pentactines (Plate 83, figs. 65-67) have very blunt, conical rays. The proximal ray is often somewhat curved ; the lateral rays are usually straight, occasionally curved in the plane, vertical to the proximal, in which they lie. The proximal ray is 0.4-1. 3 mm. long, and 15-70 m thick at the base. The lateral rays are 260-610 /x long. Those of the same spicule are usually fairly equal, more rarely conspicuously unequal. In a hypodermal pentactine with particu- larly unequal laterals the longest is 610 m in length, the shortest only 390 n. The hypogastral pentactines (Plate 83, fig. 68) are similar to the hypodermal, but much smaller. Their proximal ray is 210-800 /x long, and 12-46 ^ thick at the base. Their lateral rays are 150-460 n long. The hexactine megascleres (Plate 83, figs. 63, 64) are 0.35-5.5 mm. in maxi- mum diameter. Their rays are straight or slightly and irregularly curved, 7-120 /x thick at the base, attenuated distally, at first more gradually, then more rapidly, and pointed at the end. In all the larger and in many of the smaller ones two opposite rays are considerably longer than the other four. Some of these spicules are nearly twice as long as broad. The dermal, gastral, and choanosomal amphioxes are straight or more or less curved, rarely angularly bent, centrotyle, 0.5-2. 8 mm. long, and 7-59 ^ thick near the tyle. The tyle is 9-60 m in diameter, that is 1-23 m, usually 2-6 /x, more than the adjacent parts of the spicule. The dimensions of the different kinds of these spicules (dermal, gastral, and choanosomal) in the two specimens are given in the table on page 314. The amphioxes of the dermal and gastral membranes are in both specimens considerably shorter, stouter, and less curved than those of the choanosomal. The gastrals are in both specimens stouter than the dermals. The amphioxes of specimen h are on the whole slightly stouter than those of a. This difference is particularly well-pronounced in the gastrals. The two limbs of the angularly 314 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. Amphioxes of specimen a of specimen b dermal gastral choanosomal dermal gastral choanosomal Length limits mm. 0.56-1.7 0.6-1. 9 0.7-2. 6 0.5-1. 6 0.46-1.8 0.75-2.8 thickness limits n 11-32 0.45 8-30 12-34 7-59 8-29 Relative length (length: thickness = 10000 :) limits 28-120 24-150 58-173 23-87 22-91 83-137 average 66.9 59.6 116.8 63.2 44.3 103.3 Transverse diameter of central tyle, limits p 14-34 11-50 14-33 14-42 9-60 11-32 The tyle exceeds the adjacent parts of the spicule in thickness, by (limits) n 2-6 1-19 2-6 2-16 1-23 1-7 bent amphioxes usually enclose an angle of 130°-140°. Their bend is generally situated so much nearer one end than the other that one limb is six to eight times as long as the other, the spicule consequently having the appearance of a promonaen. Rarely the bend lies in the middle. The tyle is, as stated above, generally only 1-6 p thicker than the adjacent parts of the spicule, and in that case simply oval. Occasionally, however, much stouter tyles are observed, and in these cases it is clearly to be seen that the tyle is composed of from one to four rounded knobs representing rudimentary rays. A few spicules of this kind were triactine, a perfectly developed ray occupying the place of one of the knobs. Such triactines were observed both among the superficial and the choanosomal amphioxes. The proportion of length to thickness is in the choanosomal amphioxes of both specimens together 10000 to 58-173, on an average 10000 : 109.3. As the curve (Fig. 17), in which the reciprocal proportions (thick- ness X 10000 : length) are represented, shows, there is no great difference in the average relative thickness of the smaller and the larger choanosomal amphioxes. In the superficial (dermal and gastral) amphioxes (Plate 82, hgs. 13-19) the proportion of length to thickness is 10000 to 74-447, on an average 10000 : 241.3. Among these the shorter are, on the whole, as the following table shows, relatively much thicker than the longer. n Fig. 17. — -Amphioxes, 316 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. The relative thickness (thickness X 10000 : length) of the superficial (dermal and gastral) amphioxes of different lengths of both specimens together is shown in the following table : — Length, mm. i CO o o 1 CD 00 O O 0.81-1 1.01- 1.2 1.21- 1.4 1.41- 1.6 1.61- 1.8 1.81-2 Relative thick- ness (thickness X 10000: length) limits 177-356 109-447 09-39 07,5-445 084-346 08-393 082-159 074-147 average 279.3 309.3 231.7 217.3 156.2 202.4 118.7 101.5 This correlation between length and relative thickness comes out very clearly in the curve in the graph., Fig. 17. To ascertain whether the superficial amphioxes of varying relative thickness form a continuous series I arranged the 94 measured according to this relation and the result is represented in Figure 18. The frequency-curve of the different relative thicknesses in this figure clearly shows that, biometrically, two kinds of superficial amphioxes must be distinguished : — more slender ones, in which the proportion of length to thick- ness is 10000 : 74-210, most frequently about 10000 : 112, and stouter ones in which this proportion is 10000 : 210-447, most frequently about 10000 : 312. Among the superficial amphioxes 0.41-0.8 mm. long 82 % belong to the stout and 18% to the slender kind. 0.81-1.2 “ “ 49 % “ “ “ “ 51% 1.21-1.6 “ u 27 cy u u u u “ 73% 1.6 -2 (( q (y u u (( u o o It is to be noted that the shortest superficial amphioxes observed, that is those 0.41-0.6 mm. long, are on the whole relatively not quite so stout as those 0.61-0.8 mm. long, which are on the whole the stoutest. These smallest am- phioxes are probably young forms. Also among the spicules 0.61-1.6 mm. long there are, no doubt, some young forms of larger ones. And since the larger ones are all the slender kind these young forms will probably for the most part be young forms of the slender ones. The distal ends of the spicules of the free part of the stalk are all broken off. The parts present have a maximum thickness in specimen a of 0.8 mm., in b of 1.3 mm. The spiral twist, which all the long fragments exhibit, is such that there is one whole turn in about 23 cm. of length. The spicules forming the Relative thickness. (Thickness x 10000: length.) HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 317 upper part of the stalk imbedded in the sponge-body are not centrotyle am- phioxes. The largest one observed was 7 mm. long. The acanthophores (Plate 83, figs. 1-35) are normally composed of one to six rays. One quite abnormal one (Plate 82, fig. 24), which I found in speci- men a, has two long and six more or less reduced rays. O cn o cn Number of thickness. spicules of this relative Fig. 18. — Amphioxes. 318 HYALONEMA (OONEMA) B I AN CHORATUM PINULINA. The rare monactine and frequent diactine rhabd-forms are in specimen a 270 m-1-3 mm. long and 17-37 m thick, on an average 25.4 /x ; in b 145 ix-\A mm. long and 9-40 n thick, on an average 16 n. The more slender ones, 20 u or less thick, are, in both specimens together, 420 id-lA mm. long, the stouter ones, over 20 n thick, only 270-740 /j. long. The rare triactine and frequent tetractine forms are in specimen a 120-420 n long, with rays 20-44 n thick, on an average 31 /d] mb they are 110-500 n long, with rays 12-34 n thick, on an average 22.4 /x. The pentactine and hexactine forms, both of which are not numerous, are in specimen a 180-350 /x long, with rays 15-24 n thick; in b they are 80-390 n long, with rays 8-25 n thick. The rays of the tri- to hexactines usually differ in length more or less, often very considerably. The rays of the tri- and tetractines always extend in one plane, whilst the pentactine and hexactine forms resemble, in respect to the position of their rays, the pentactine and hexactine megascleres above described. The rays are more or less, exceptionally (Plate 82, figs. 11, 12) very considerably, curved and nearly always simple, very rarely branched (Plate 82, fig. 17). They are cylindrical or cylindroconical, not infrequently somewhat uneven, and rounded and usually thickened at the end. The terminal thickenings are particularly well-developed in the rhabd-forms, and these usually also have a central tyle. In a fairly typical diactine spicule of this kind, 1 mm. long and 16 /d thick, the central tyle is 18 n in transverse diameter, and the terminal tyles 30 /x and 34 ^ respectively. The central tyle is either well-defined (Plate 83, fig. 5) or not (Plate 83, fig. 1). In all the larger and a good many of the smaller basal spicules, the proximal and middle-parts of the rays are smooth, apart from the occasional slight undulations of their surface. The end-parts are nearly always densely spined, or exceptionally smooth (Plate 82, figs. 19, 20, 34). A good many of the smaller basal spicules (Plate 82, figs. 10, 18, 28-30) are entirely spined, the spines on their proximal parts being usually slightly smaller than those on their distal parts. The entirely spined forms are much more frequent among the basal spicules of specimen a than among those of b. The spines are broad and conical. Those measured were 2-6 n long, rarely up to 10 id. The spicules forming the skeleton of the Palythoa attached to the stalk of specimen a (Plate 83, figs. 36-44, 46-59) are monactine to tetractine. The rare monactine and frequent diactine rhabd-forms are 122-520 n long and 20-40 ii thick, on an average 32.4 n. The rare triactine and frequent tetractine forms are 90-290 n long and 20-40 n thick; the average thickness is 31.6 n. HYALONEMA (OONEMA) B I AN CHORATUM PINULINA. 319 These spicules are similar to the corresponding basal spicules of specimen a, and differ from these only by being thicker and more spiny. While in the majority of the acanthophores in the sponge the proximal and middle-parts of the rays are smooth and only the distal part spiny, we find among the (similar) spicules of the Palythoa skeleton relatively many fewer with rays smooth in their proximal part, the majority being here entirely spined. it is to be noted also that the spicules of the Palythoa skeleton have, on the whole, larger spines than the corresponding spicules in the basal part of the sponge. In the larger spicules of the Palythoa skeleton the spines are on the distal parts of the rays very much larger than on their proximal parts. In the smaller forms this difference is not nearly so conspicuous, and in the smallest all the spines appear to be fairly equal in size. The largest spines measured were 15 /x long, and 14 n broad at the base. The average thickness of the rays of the rhabd acanthophores of specimen b is 16.0 n “ “ “ “ “ “ a “ 2.5.4 /d “ “ “ “ “ the Palythoa on the stalk of specimen .. a “ 32.4 /u “ “ tri- to tetractine acanthophores of specimen b“ 22.4^ “ “ “ “ “ “ “ “ a “ 31.0 m “ “ “ “ “ “ “ the Palythoa on the stalk of specimen a “ 31.6 ju Thus these spicules are in a much stouter than in b, and in the Palythoa attached to the stalk of a thicker than in the sponge itself. The fact that the Palythoa spicules are, on the whole, stouter and more spiny than those of the sponge is, no doubt, due to the Palythoa selecting for the purpose of building its skeleton the stoutest and most spiny of the spicules shed by the sponge. That these spicules are in a (on the stalk of which Palythoa polyps with sponge-spicule skeletons grew) much stouter than in b (the symbio- tic polyps of which have no skeleton) either may have nothing to do with their symbiotic polyps, and be in respect to them accidental; or it may be due to an influence of the spicule-requiring Palythoa on the sponge, comparable to that of a gall-wasp clutch on the vegetable tissue surrounding it; an influence which, in this case, might cause the sponge to produce abnormally stout and spiny acanthophores. The microhexactines (Plate 82, figs. 2-11, 20), which are the same in both specimens, have equal, regularly arranged rays and measure 57-152 ^ in total diameter. The rays are 2-3.8 n thick at the base, conical, and attenuated distally to a fine point. They are straight in their proximal part and usually curved 320 HYALONEMA (OONEMA) BIANCHGRATUM PINULINA. in their distal part, more rarely straight throughout. The curvature is such that the tangents of the end-parts of the rays enclose angles of 120°-150°, excep- tionally only 90°, with the continuation of the axis of their proximal parts. The proximal end-part of the rays is smooth for a short distance, the distal end- part for a considerable distance. The remaining, middle-part bears spines as much as 0.7 m long, which are generally vertical. As stated above, I think it probable that the straight-rayed microhexactines are canalaria, and only the curved-rayed ones true parenchymalia. In specimen b I found a microhexactine-derivate with only one ray. This monactine spicule appears as a spined tylostyle curved towards its pointed end. Its measurements are:- — length 105 m; basal thickness of single ray 4.5m; tyle 8.5 m- Morphologically two kinds of amphidiscs can be distinguished : — those with stout shaft and relatively broad anchors; and those with slender shaft and rela- tively narrow anchors. To study them biometrically I measured 275 (134 of specimen a and 141 of specimen b) and drew Figure 19, in which the length frequency-curves of the amphidiscs are represented as follows: — of specimen a ( ) ; of speci- men b ( ) ; and of both specimens together ( ) . In specimen a the amphidiscs are 18-480 m long. Their length frequency- curve ( ) exhibits two main elevations at about 33 m and about 164 n, a number of small elevations, and three large gaps between .54 and 79 m, between 90 and 110 m, and between 200 and 220 m- The amphidiscs 18-54 m and 79- 90 m long are all thin-shafted and narrow-anchored; those 110-200 m and 220- 480 m long are all thick-shafted and broad-anchored. The amphidiscs of specimen b are 21.5-492 m long. Their length frequency- curve exhibits two main elevations corresponding exactly to the two main elevations of the curve for specimen 5; a number of small elevations, some of which correspond to the small elevations of b, and some of which do not so correspond; and three principal gaps between 66 and 79, 87 and 118 m, and 187 and 212 m- The amphidiscs 21.5-66 m and 79-87 m long all belong to the thin-shafted slender-anchored kind, those 118-187 m and 212-492 m long to the stout-shafted, broad-anchored kind. In both specimens therefore two main groups of amphidiscs can be dis- tinguished both morphologically and biometrically : — macramphidiscs with stout shaft and broad anchors, in both specimens together 110-492 m long, and micramphidiscs with thin shaft and slender anchors, in both specimens together Length of Amphidiscs (m). HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 321 15.86— 17.45 — | ' 1 1 1 Y | l 1 17.45— 19.19- >! !i 19.19— 21.11- Rl 1 1 21.11 — 23.23- 23.23— 25.55- 25.55— 28.10- : 1 i i -hy,~r 28.10- 30.91- - 1- i-l-i-* ill 30.91- 34.00- 1 1 1 1 vr\r 34.00— 37.40- 1 1 “I ~Cy 37.40— 41.14- -J-cj-j-J- 41.14— 45.26- 1 1 * / 45.26— 49.78- 49.78— 54.76- 54,76— 60.24- , :< 60.24— 66.26- -I-I4-P 66.26— 72.89- 72.89— 80.18- m i 80.18— 88.20- - V\ i i A « ' ! 88.20— 97.02- /. i ' 7/ i 1 ! 97.02 — 106.72- /, i 1 , |i i ' i 106.72- 117.39- \i ! ! 117.39-129.13- 129.13 — 142.04 142.04 — 156.25— 156.25—171.87 171.87 — 189.06 189.06 — 207.97 207.97 — 228.76 228.76 — 251.64— K’-i 251.64 — 276.81 -V 276.81 - 304.49 - 1 . 304.49 - 334.93 -|0 334.93 — 368.43 368.43 — 405.27 405.27 — 445.80 — «. 445.80 — 490.38 490.38 — 539.41 539.41 — 593.35 cn Number of Amphidiscs > Small Micramphidiscs. > Large Micramphidiscs Small Macramphidiscs. Large Macramphidiscs. Fig. 19. — 'Amphidiscs. 322 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 18-90 n long. It is to be noted that the macramphidiscs are much more numer- ous in a than in 6, while the micramphidiscs are much more numerous in b than in a. In consequence of this the number of macr- and micramphidiscs measured and plotted in the figure are very different in the two specimens, and the sum- mits of the two main elevations of the a- and 6-curve are very different in height. The larger (longer) macramphidiscs differ from the smaller (shorter) ones morphologically by having relatively shorter anchors. The length frequency- curves of the macramphidiscs show that these spicules by no means represent a biometrically homogeneous group in respect to their length. The parts of the macramphidisc curves below (to the left of) the above mentioned gaps between 200 and 220 p in a and between 187 and 212 p in 6 are very regular and obviously pertain to biometrically homogeneous groups; the parts of these curves above (to the right of) the gaps are on the other hand very irregular 1 and in no way in harmony with the others below (to the left) of them. I there- fore think that the group macramphidiscs should be subdivided into two secondary groups : — large macramphidiscs with relatively short anchors, in both specimens together 212-492 p long; and small macramphidiscs with relatively long anchors, in both specimens together 110-200 p long. The length frequency-curves of the micramphidiscs of both specimens exhibit, besides the single main elevation, a number of small elevations. Most of these are, as in the case of the large macramphidiscs, probably due to the scarcity of the micramphidiscs of these sizes, which made it impossible to meas- ure a larger number of them. Some of these elevations (two in the a-curve; and one in the 6-curve, corresponding to one of the former) pertaining to the largest micramphidiscs are, however, separated from the rest of the micramphi- disc curves by very conspicuous gaps (between 54 and 79 p in the a- and between 66 and 79 p in the 6-curve). I therefore think it well to divide the micramphi- discs according to these gaps into two subgroups: — large micramphidiscs, in both specimens together 79-90 p long; and small micramphidiscs, in both speci- mens together 18-66 p long. The chief dimensions of the large macramphidiscs (Plate 85, figs. 1-7) are tabulated on page 323. In these amphidiscs the shaft is straight and usually centrotyle. It is either quite smooth (Plate 85, fig. 7) or bears a few low rounded knobs (Plate 85, figs. 2, 4-6), sometimes also a single, straight, cylindrical, terminally rounded spine (Plate 85, fig. 1), which arises from its centre (central tyle). Occasionally 1 These irregularities are partly at least probably due to the rarity of these spicules, which made it impossible to measure a larger number of them. HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 323 of specimen a of specimen b of both speci- mens together Length n limits 220-480 212-492 212-492 most frequently about 240, 320, 468 277, 387, 468 468 Shaft, thickness, limits n 17-26 19-28 17-28 Central tyle transverse diameter of tyle, n limits * 17-31 19-32 17-32 the tyle thicker than the shaft by ,u, limits • 0-8 0-9 0-9 length, limits ^ 90-122 94-140 90-140 breadth, limits £i 148-195 140-210 140-210 Terminal proportion of anch- or-length to anchor- breadth limits 100 to 141-177 131-189 131-189 anchors average 100 to 161.4 158.6 160.1 proportion of anch- or-length to total length of whole spi- cule limits 1 : 2. 1-3.9 average 1: 3.2 a stout knob or two are observed also on other parts of the shaft (Plate 85, figs. 1, 2). The single large spine on the central tyle is, in the normal large macramphidiscs, sometimes 21 n long and 14 n thick. I have never seen more than one such large spine on a normal spicule of this kind. In a few abnormal large macramphidiscs I observed (Plate 85, fig. 3) one or two clusters of verticils of projections arising some distance from the middle of the shaft. These had a maximum length of 45 ix, and were inclined or curved towards the centrum. They appear to be supernumerary anchor-teeth. The proportion of the terminal anchor to the total length of the whole spicule is (in both specimens together), as stated above, 1 to 2. 1-3.9, an average of 1 : 3.2. The difference between total length and anchor-length is the greater the larger the spicule. In the large macramphidiscs 400 p and more in length the above proportion is 1 : 3. 2-3. 9, in those under 300 p in length 1 : 2.1-3. The anchor-teeth are about 30 n broad and pointed at the end. They arise nearly vertically from the shaft and are quite strongly curved in their proximal, and straight in their distal part. Their total curvature is such that their end- parts diverge at an angle of 12°-22° from the shaft. The chief dimensions of the s?nall macramphidiscs (Plate 83, fig. 45c; Plate 84, figs. 3-13, 26-32) are: — 324 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. of specimen a of specimen b of both speci- mens together Length n limits 110-200 118-187 110-200 most frequently about 164 164 164 Shaft, thickness, limits n 13-20 14-20 ' 13-20 length, limits n 0 46-87 50-81 46-87 breadth, limits tx . 74-135 85-126 74-135 Terminal anchors proportion of anchor- length to anchor- breadth limits 100 to 153-185 130-172 130-185 average 100 to 167.5 153 6 161.1 proportion of anchor- length to total length of the whole spicule limits 1 : 2-2.5 average 1 : 2.3 In these amphidiscs the shaft is straight, regularly cylindrical, destitute of a central tyle, and perfectly smooth. The proportion of the length of the anchors to the total length of the whole spicule is in both specimens together, as stated above, 1 to 2-2.5, on an average 1 : 2.3. The difference between total length and anchor-length is in the small macramphidiscs, in contradistinction to that of the large, on the whole the greater the shorter the spicule. In the longer small macramphidiscs, over 180 n in length, the above proportion is 1 to 2. 2-2. 3, in the shorter, under 130 n in length, 1 to 2. 4-2. 5. The terminal anchors are composed of from eight to twelve teeth. Eight is the most frequent number, but small macramphidiscs with from nine to twelve are by no means rare and in no way abnormal. The position of the teeth of the two terminal anchors of the same spicule is alternate. The individual teeth have a T-shaped transverse section. The upper band-shaped part is, in its middle-part, 22-30 n broad and attenuated both distally and proximally (Plate 82, fig. 26). It is not only longitudinally, but also transversely curved, concave to the shaft (Plate 84, fig. 27), and usually rounded, very rarely pointed, at the end. The keel, that is the part corresponding to the lower stroke of the T, is low distally but attains a great height and thickness proximally (Plate 84, figs. 26, 28, 32). The outer contour of the tooth, when seen in profile, appears as a line strongly curved near the base and at the tip, but only slightly curved in its middle-part. The middle-part of this line diverges at an angle of 20-30° from the shaft; its end-part is convergent to the shaft. The end-parts of the HYALONEMA (OONEMA) BIANCHORATUM PINUL1NA. 325 inner contour (the inner margin of the keel) and the lateral margin, on the other hand, diverge from the shaft. In specimen a I found a remarkable abnormal small macramphidisc (Plate 85, fig. 8) 190 m long, with terminal anchors respectively 80 and 100 n long and about 100 m broad. In this spicule each anchor is composed of two partly incomplete and somewhat irregular verticils of anchor-teeth, instead of a regu- lar single one. This duplication is much more pronounced in one (the upper one in the figure) than in the other terminal anchor. Some of the teeth belonging to the inner (supernumerary) verticils are nearly straight, extend obliquely backwards, and are widened at the end to irregularly oval terminal discs. The position of these terminal discs is such that if the whole amphidiscs were assumed to be enclosed in a tight-fitting ovoid mantle or shell, the outer faces of the terminal discs would come to lie exactly in the (inner) surface of such mantle or shell. This observation seems to me to be of similar import as the one on an abnormal amphidisc found in Hyalonema ( Prionema ) agujanum var. tenuis (p. 262, Plate 75, figs. 35-37); both favor the view that each amphidisc is formed within a single ovoid cell. The chief dimensions of the large micr amphidiscs are: — of specimen a of specimen b of both speci- mens together Length p limits 79-90 79-87 79-90 most frequently about 85 82 84 Shaft, thickness, limits p 4 3.5 3.5-4 Central transverse diameter of tyle, limits p 4 4 tyle the tyle thicker than the shaft by, limits yu 0.5 0.5 length, limits /x 26-35 26-29 26-35 breadth, limits yu 23-40 23-25 23 40 Terminal anchors proportion of anchor- length to anchor- breadth limits 100 to 80-114 83-88 80-1 14 average 100 to 79 86.3 91.2 proportion of anchor- length to total length of whole spicule limits 1: 2. 4-3. 2 average 1: 2.8 In these amphidiscs the shaft is straight. The central tyle is not defined and passes gradually into the adjacent part of the shaft. Tyle and shaft are very spiny. 326 HYALONEMA (OONEMA) BIANCHORATUM PINULINA. The chief dimensions of the S7nall micramphidiscs (Plate 84, figs. 15-25) are : — of specimen a of specimen 6 of both speci- mens together Length n limits 18-54 21.5-66 18-66 most frequently about 33 33 33 Shaft, thickness, limits /u 1-1.7 1-2.5 1-2.5 Central transverse diameter of tyle, limits ju 1-3 1-4.5 1-4.5 tyle the tyle thicker than the shaft by, limits n 0-1.6 0-2.5 0-2.5 length, limits n 7-20 6.5-23.5 6.5-23.5 breadth, limits n 7-17 8 . 5-23 7-23 Terminal anchors proportion of anchor- length to anchor- breadth limits 100 to 77-128 80-146 77-146 average 100 to 97.4 102.6 100.6 proportion of anchor- length to total length of whole spicule limits 1: 2.7-4 average 1: 3.2 In these amphidiscs the shaft is usually straight, rarely curved. In some place at or near the middle it is thickened, gradually in the larger, more abruptly in the smaller, to a rather stout central tyle. In the larger forms the tyle and the adjacent parts of the shaft, about one third of its total length, are densely cov- ered with spines sometimes 1 ^ long. The end-parts of the shaft of these am- phidiscs are smooth or only roughened by exceedingly minute spines. In the smaller forms the spines on the shaft are so small that they can hardly be made out as such, and merely render the shaft somewhat rough in appearance. The anchor-teeth are curved rather strongly in their proximal part, but only slightly or not at all in their distal part. Their end-parts are generally slightly divergent. A few abnormal small micramphidiscs were found in specimen b. In one of these, 26 m long, a straight cylindrical branch arises very obliquely from the shaft. This branch is as thick (1.6 m) and half as long as the shaft, and broken off at the end. In another small micramphidisc (45 m long, with termi- nal anchors 19 n long and 22 /x broad), two opposite rays lying in the same straight line and both vertical to the shaft arise from the centrum of the spi- cule. These rays are straight, as thick as the shaft (2 n), and, like the shaft, HYALONEMA (OONEMA) HENSHAWI. 327 covered with spines. One of them is broken off short; the other, which is intact, is 23 m long and bears on the end a narrow and pointed anchor-rudiment 10^ long and 8 u broad, similar in appearance to a half closed umbrella. There can be no doubt that the two sponges above described belong to the same systematic unit. There can also be no doubt that they are very nearly related to the sponge described by Wilson 1 as Hyalonema bianchoratum. Indeed the similarity between them is so great that the Albatross specimens must be considered as a variety of the species described by Wilson. The distal ray of the largest pinules is in the typical Hyalonema bianchora- tum Wilson very much longer than in the sponges above described. Also in shape the pinules do not quite agree, and while all the pinules of the former are pentactine, some of the pinules of the latter are hexactine. The hypodermal and hypogastral pentactines are larger in the former than in the latter. The microhexactines of Wilson’s type do not attain so large a size and have stouter rays than those of the variety pinulina. The shafts of the large macramphi- discs are in the former stouter than in the latter. The small macramphidiscs have in the former a centrotyle shaft and eight anchor- teeth ; in the latter a simple cylindrical shaft without tyle and quite often more than eight, some- times as many as twelve, anchor-teeth. These differences, although insufficient for specific distinction, are quite sufficient for varietal distinction. I therefore divide Wilson’s Hyalonema bianchoratum into two varieties: — var. typica (for Wilson’s type) and var. pinu- lina (for the sponges above described). Hyalonema (Oonema) henshawi, sp. nov. Plate 97, figs. 1-36; Plate 98, figs. 1-7. One specimen of this species was trawled in the Eastern Tropical Pacific at Station 4649 on 10 November, 1904; 5° 17' S., 85° 19.5' W. ; depth 4086 m. (2235 f.); it grew on a bottom of sticky, gray mud; the bottom-temperature was 35.4°. I name it after the Director of the Museum of Comparative Zoology, Mr. Samuel Henshaw. Shape and size. The single specimen (Plate 97, fig. 15) has the shape of a deep, conical cup, rounded off below. The upper margin is lacerated. The stalk, which, in life, doubtlessly projected from its lower end, has been com- 1H. V. Wilson. Mem. M. C. Z., 1904, 30, p. 22, pi. 2, figs. 1-11. 328 HYALONEMA (OONEMA) HEN SHAWI. pletely torn off. The cup is 123 mm. long and above, at the margin, 80 mm. in transverse diameter. The wall of the cup is only 6 mm. thick. A great part of the dermal membrane is lost; of the gastral membrane extensive tracts are present. The lower part of the gastral membrane, which lines the deeper parts of the cavity of the cup, appears to contain but few efferent pores. Exten- sive pore-sieve nets, with pores sometimes 1.7 mm. in diameter (Plate 97, fig. 32), occur in its upper part. The colour in spirit is rather dark dirty brown. The skeleton consists of dermal, gastral, and canalar pinules; hypodermal and hypogastral pentactines; superficial paratangential and choanosomal more or less radial amphioxes; choanosomal hexactine megascleres; abundant mi crohexac tines in all parts of the body ; and three kinds of amphidiscs, macram- phidiscs and large and small micramphidiscs. The dermal pinules (Plate 97, figs. 2, 31) are nearly always pentactine, hex- actine forms being met only exceptionally. The distal ray is straight, ISO 600 n long, most frequently about 390 and 10-22 /x thick at the base. It ends in a terminal cone and bears spines, which are short, conical, and vertical on its basal part, but strongly inclined and large, sometimes 25 m long, farther up. The maximum thickness of the distal ray, together with the spines, is 15-68 /x; in those rays over 500 /x long this thickness is always over 40 The lateral rays are 37 /x-70 n long; in the dermal pinules with a distal ray over 500 /x in length the lateral rays are always over 50 m long. These rays are cylindroconical or nearly cylindrical, and rounded at the end. They bear a few scattered spines, which usually congregate a little beyond the middle of the length of the ray. The proximal ray of the few hexactine forms is 15-75 ^ long. The dermal pinules of the lower part of the body appear to be on the whole shorter than those of the upper part. Among the former a fair number with distal rays only 260- 280 long have been observed, while the distal ray of the latter is only quite exceptionally less than 320 m long. The gastral pinules (Plate 97, figs. 1, 3-5, 29, 30) are similar to the dermal, and like them nearly always pentactine, exceptionally hexactine. Their distal ray is straight, 142-710 m long, generally 342-650 /x, and at the base 12-27 /x thick; in those over 600 n long, always 20 /x or more thick. The spines on the distal ray of these gastral pinules appear to be stouter, shorter, and less inclined than those on the distal ray of the dermal. The maximum thickness of the distal ray, together with the spines, is 25-85 /x; in those over 600 m in length this thickness is always over 64 yix and usually about 80 yu, The lateral rays HYALONEMA (OONEMA) HENSHAWL 329 are similar to those of the gastrals and 42-70 n long. The proximal ray of the single hexactine form observed is 30 p. long. The canalar pinules (Plate 97, fig. 6) are pentactine or, more rarely, hexac- tine. The distal ray is 120-220 /x long and 6-10 n thick at the base. The lateral rays are 53-110 n long; the proximal ray is, when present, 28-65 m long. All the rays are pointed, conical, and spined. The spines are very small, so that, even with the spines, the distal ray is nowhere thicker than at its base. The hypodermal and hypogastral pentactines. A large number of hypodermal pentactines were observed, but few hypogastral. The hypogastrals and hypo- dermals appear to be quite similar. Their rays are straight, smooth, conical, and blunt. The proximal ray is 550-900 n long and 26-47 n thick at the base. The lateral rays are 320-650 n long. The hexactine megascleres are 0.6-1 .4 mm. in diameter, and have fairly straight, conical, and blunt rays, 13-32 n thick at the base. The amphioxes are centrotyle, nearly straight or curved, rarely angularly bent near one end. They are 0.9-1. 6 mm. long and 8-23 /x thick near the middle. The central tyle is 12-27 n in transverse diameter, that is 1-6 /x more than the adjacent parts of the spicule. The rays of the microhexactines (Plate 97, figs. 33-36) are nearly always perfectly straight; only quite exceptionally one of the rays exhibits a slight curvature. The microhexactines are 108-230 /x in diameter, generally 1 10 190 m, and their conical, pointed rays are 3.5-7 /x thick at the base. The rays bear spines, the largest of which are 0.7-1. 5 n long. Generally the spines are sparsely scattered over the greater part of the length of the ray, leaving the distal end-part free for a distance of about 10 m- The proximal spines are vertical, the distal inclined backwards. Among the amphidiscs two kinds can be clearly distinguished morphologi- cally: — A, a stout kind with large anchors, about half the length of the whole spicule; and B, a slender kind with small anchors, much less than half, usually about a third, of the whole spicule in length. The length frequency-curve (Figure 20) has three main elevations sepa- rated by deep depressions. The part of the curve to the right of 106.72, the summit of which lies at about 179, pertains to the morphological group A, and comprises all amphidiscs of this kind. The deep depression (down to 0) between this part of the curve and the other parts shows that the amphidiscs it pertains to form a distinct group. This coincides with their morphological character, and so a special group must doubtlessly be established for these 330 HYALONEMA (OONEMA) HENSHAWI. amphidiscs, which, as they are the largest forms, I name macramphidiscs. All the other amphidiscs differ morphologically from these but are similar among themselves. They can, as they comprise the small forms, be named micramphi- discs. The part of the curve pertaining to these micramphidiscs is divided by the deep depression at about 63.2 into two parts, one comprising the larger, the other the smaller forms. Although the larger of these amphidiscs are very similar morphologically to the smaller, there could, after their biometrical study had pointed the way, be found certain morphological differences between them, particularly in the curvature of the anchor-teeth, which corroborate their biometrical distinction, and which, although slight, in my opinion justify a division of the micramphidiscs into two subgroups : — large micramphidiscs over 63.2 /x in length, and small micramphidiscs under that. HYALONEMA (OONEMA) HENSHAWI. 331 I do not think that any importance is to be attached to the minor irregu- larities of the curve, although some of these, particularly those in the part of it pertaining to the small micramphidiscs, are not inconsiderable. According to the above three kinds of amphidiscs are to be distinguished - macramphidiscs, larger forms with relatively large anchors; large micramphi- discs, forms of medium size with rather small anchors; and small micramphi- discs, small forms with rather small anchors. The macramphidiscs (Plate 97, figs. 7-14; Plate 98, figs. 1-7) are 1 14 — 227 n long, most frequently about 179 m- The shaft is cylindrical, smooth, straight, and 12-20 n thick. The terminal anchors are 50-111 n in length, about half of the whole spicule, and 70-169 n broad. The proportion of the length to the breadth of the anchors is 100 to 123-187, generally 100 to 136— 178, on an average 100 : 156.8. The number of the teeth in an anchor is usually eight. The teeth of the two anchors of the same spicule are situated alter- nately, but this alternation is often somewhat irregular, the adjacent anchor- teeth planes (of opposite teeth) not intersecting at exactly 22.5°. The outer contour of the individual teeth is curved considerably in its basal part for about 0.4 part of the length of the tooth, curved only slightly beyond that up to about 0.8 of this length, and curved again strongly at the end, so that the tips of the teeth become strongly convergent. The outer band-shaped patt of the tooth attains its maximum width somewhere beyond the middle of its length, and here measures 20-31 m in transverse diameter. The tip of the tooth is rounded or, more rarely, somewhat pointed, like a gothic arch. The keel, in the larger forms, is over 30 fi high at the base, and becomes gradually lower distally. It terminates before reaching the end of the tooth. Somewhat irregular forms are not infrequent among these amphidiscs. Considerable inequalities in the two anchors of the same spicule (Plate 98, fig. 6) or in the teeth of the same anchor (Plate 98, fig. 4) are often met, and some- times irregularities occur on the apices of the anchors (Plate 98, fig. 7). The large 'micramphidiscs (Plate 97, figs. 16-20) are 67—9 1 m long, most frequently about 69.5 n. The shaft is straight, centrotyle, and 2-4 ^ thick. The tyle passes gradually into the adjacent parts of the shaft. It is 3.5-5 m in transverse diameter, that is 0.5-3 m more than the adjacent parts of the shaft. With the exception of its end-parts, the whole shaft is covered with spines. The spines on the tyle are much larger than the others, sometimes 3 n long, and often strongly curved. The terminal anchors are 20-35 m, usually a little more than a third of the whole spicule in length. Their breadth is 18- 332 HYALONEMA (OONEMA) CRASSIPINULUM. 30 n. The proportion of anchor-length to anchor-breadth is 100 to 69-100, on an average 100 : 89.5. The teeth arise nearly vertically from the ends of the shaft, and are curved strongly at the base and decreasingly towards the end. The tips of the teeth are usually parallel or slightly divergent. The s?nall micramphidiscs (Plate 97, figs. 21-28) are 24-57 i± long, most frequently about 32.4 /x. The shaft is 0.8-2 n thick, and generally centrotyle. The central tyle is 1.8-2. 6 n in transverse diameter, that is 0.3-1 n more than the adjacent parts of the shaft. Small spines are scattered over tyle and shaft- in the larger forms; in the smaller these spines are so minute that it is diffi- cult to make them out, often they appear to be absent altogether. The anchors are 7-22 n long, usually about a third of the whole spicule. The anchor-breadth is 7-19 ix. The proportion of anchor-length to anchor-breadth is 100 to 71-121, on an average 100 : 89.7. The teeth are sometimes remarkably numerous. They arise vertically from the ends of the shaft and are more strongly curved some distance from the base than proximally; beyond the strong bend, they decrease in curvature, so that their end-parts are nearly straight and parallel. The teeth are pointed at the end. The nearest allies of the above sponge are the species Hyalonema ( Oonema ) densum, H. (O.) sequoia, and H. (O.) crassipinulum described in this Report. From these it differs by being destitute of the large macramphidiscs. From H. (O.) densum also it differs by having straight-rayed micramphidiscs, and from the other two also by its superficial pinules being smaller and their distal rays much more slender. Hyalonema (Oonema) crassipinulum, sp. nov. Plate 92, figs. 1-23; Plate 93, figs. 1-10; Plate 94, figs. 1-33. One specimen of this species was trawled in the Central Pacific at Station 3684 (A. A. 17) on 10 September, 1899; 0° 50' N., 137° 54' W. ; depth 4504 m. (2463 f.) ; it grew on a bottom of light yellow-gray Globigerina ooze. It possesses pinules with large, remarkably divergent spines on the proximal part of the distal ray. To this the name refers. Shape and size. The single specimen (Plate 93, fig. 9) has the shape of an inverted bell, 105 mm. long, 95 mm. broad, and now strongly compressed later- ally and only about 18 mm. thick. In life the sponge was probably laterally com- pressed much less, or not at all. A stalk, 2.5 mm. thick and broken off rather short, protrudes from the lower rounded end. The lower and lateral surfaces, HYALONEMA (OONEMA) CRASSIPINULUM. 333 which are the dermal, are continuous and fairly smooth. The upper surface, which is the gastral, now appears rugose. In life wide cavities, separated by upright walls, probably occupied the upper part of the interior. Reticulate pore-sieves are observed on some parts of the surface. Indications of flagel- late chambers about 140 ju in diameter were noticed in some of the sections. The colour in spirit is light dirty brown. A small colony of Palythoa polyps is attached to the upper part of the stalk. The skeleton. A fur composed of distal rays of large pinules covers the whole sponge. The gastral pinules, particularly those on the pore-sieves, are very large, the dermal considerably smaller. Very numerous large micramphi- discs lie in and on the surface. Microhexact.ines, paratangentially extending amphioxes, and the lateral rays of pentactines occur just below the lateral rays of the superficial pinules. Some hexactine and abundant rhabd megascleres, very numerous microhexactines, a few monactine microhexactine-derivates, canalar pinules, and amphidiscs are found in the interior. The internal amphi- discs are of four kinds: — 1, very scarce large macramphidiscs; 2, not numer- ous small broad-anchored macramphidiscs; 3, very scarce small macramphi- discs; and 4, very numerous micramphidiscs. It is possible, but not probable, that 1 and 3 are foreign spicules. Numerous acanthophores for the most part diactine and tetractine occur in the basal part of the sponge-body. The canalar pinules are rare, and found only here and there in the canal-walls. In the walls of some of the canals masses of micramphidiscs are observed. The remnant of the stalk consists of a few stout and several slender spicules. In the superficial part of the coenenchym and in the lateral and oral walls of the individual polyps of the Palythoa, spicules occur in large numbers; these are similar to the smaller and stouter acanthophores of the basal part of the sponge. The gastral superficial pinules have a distal ray 250-1130 n long (measured in the case of the curved ones along their chord). The length frequency-curve of the distal ray has two distinct elevations, at about GOO and 850 ^ . This indicates that two kinds of gastral pinules, a large and a small, should be dis- tinguished. The large gastral pinules (Plate 92, figs. 1-4, 20, 22, 23), which greatly preponderate in the reticulate pore-sieves, are all pentactine. Their distal ray is straight or, comparatively very frequently, curved in its distal part. The curvature is usually not great but sometimes very marked. In one of these 334 HYALONEMA (OONEMA) CRASSIPINULUM. pinules the distal part of the axis of the distal ray enclosed an angle of nearly 90° with its proximal part. The distal ray is (measured in the case of the curved ones along the chord) 680-1130 n long, most frequently 800-950 n, 20-35 n thick at the base. Above it thickens considerably, and attains at its point of maximum thickness, which lies a little above the middle of its length, without the spines, a transverse diameter usually a little more than twice as great as that of its base. At its distal end the ray is attenuated very abruptly to a blunt point or is, exceptionally, rounded and dome-shaped. The proximal part of the distal ray bears short and very stout, vertical, conical spines, which extend quite down to its base. Farther on the spines become longer, curved, concave towards the shaft and more and more inclined towards its distal end. The longest spines attain a length of 20-40 /x. The spines are usually regularly arranged; only occasionally an irregular arrangement of those occupying the concave side of curved distal rays is observed. The maximum diameter of the distal ray, together with the spines, is 75-115 m- The lateral rays are, at the base, slightly thinner than the proximal end of the distal ray. They are nearly cylindrical in their proximal and conical in their distal part, very blunt, 64- 150 n long, and spinecl. The spines are quite numerous, very stout, vertical, conical, and generally up to about 6 n long. The small gastral pinules (Plate 92, figs. 5, 18, 21) are likewise all pentac- tine. The distal ray is generally straight, 250-640 /z long, most frequently 500-640 ii, and 12-28 n thick at the base. Above it thickens very consider- ably and attains without the spines, at the point of maximum thickness, which lies a little above the middle, a transverse diameter two to five times as great as that of its base. Distally the ray is attenuated more gradually than in the large gastral pinules, so that its end appears more slender. The distal ray is covered with spines down to its base. The spines increase in length up to a point a little beyond the middle of the ray, where they are sometimes 20-30 /x long. Beyond they again decrease in size. The lowest spines are, like those of the larger gastral pinules, short, stout, conical, and vertical; but as we pro- ceed in a distal direction and the spines become longer, their tips curve upwards more and more, and a short distance below the middle of the ray they pass, often quite abruptly, into spines inclined and bent towards the end of the ray to such an extent that their end-parts are very strongly inclined, parallel, or even convergent. The distal part of the ray consequently has an appear- ance very different from that of its proximal part, the former looking nearly smooth, the latter bristling with large spines. The lateral rays are similar in shape to those of the large gastral pinules, but only 50-125 m long. HYALONEMA (OONEMA) CRASSIPINULUM. 335 The dermal superficial pinules have distal rays 250-790 n long. Their length frequency-curve exhibits, like that of the gastrals, two very distinct elevations, so that also among these pinules two kinds, a large and a small one, must be distinguished. The large dermal pinules (Plate 92, fig. 6) are pentactine. Their distal ray is usually straight and 500-790 /x long, most frequently 600-650 /x- It is 15-24 /x thick at the base, and thickened above. At its point of maximum thickness, which lies a little above the middle, it attains a transverse diameter about twice as great as its basal thickness. The distal ray ends with a low and broad termi- nal cone. Its spinulation is similar to that of the gastral pinules. The spines are proportionately smaller. The maximum diameter of the distal ray, together with the spines, is 50-90 /x. The lateral rays are cylindroconical, and 45-95 n long. They bear small, sparse, broad, and low, conical spines. The synall dermal pinules (Plate 92, figs. 7, 18) are rather similar to the larger ones and, like them, all pentactine. Their dimensions are: — distal ray, length 250-440 /x, basal thickness 10-17 /x, maximum thickness together with the spines 28-65 /x; lateral rays, length 45-70 n- The canalar pinules (Plate 92, figs. 16, 17) are pentactine or hexactine. The distal ray is straight, 120-150 /x long, and 5-9 n thick at the base. It is slightly thickened above, gradually attenuated to a line point, and bears rather sparse, small, straight spines directed obliquely upwards. Its maximum thick- ness, together with the spines, is 7-30 /x. The lateral rays are 45-95 tx long; the proximal, when present, is 50-70 /x. Both the lateral rays and the proximal are spiny. There seems to be no great difference between the hypodermal and hypo- gaslral pentactines. Both have straight, conical, blunt rays. The lateral rays are 230-550 /x long; the proximal ray is 400-700 /x long and 15-60 /x thick at the base. The hexactine megascleres generally have fairly equal rays. In some, two opposite rays are a little longer than the others, but the difference never appears to be great. The hexactine megascleres observed are 0.8-1. 2 mm. in diameter. The basal thickness of their rays is 25-30 m- The amphioxes of the dermal and gastral membranes (pore-sieve reticula- tions) and the choanosome are centrotyle, straight or curved, sometimes very considerably, and 0.7-1. 7 mm. long. Near the middle they are 8-29 ^ thick. The central tyle is 10-34 /x in diameter, that is 2-5 ^ more than the adjacent parts of the spicule. 336 HYALONEMA (OONEMA) CRASSIPINULUM. In the axial part of the sponge a few much larger amphioxes were observed; they had a maximum length of 8 mm. and were 160 /z thick. These appear to take part in the formation of the upper end-part of the stalk, which is imbedded in the body of the sponge. The spicules of the stalk are broken off rather short. Where they arise from the body of the sponge they are 50-500 /z thick. The acayithophores in the sponge-body (Plate 94, figs. 24-33) are mostly diac- tines and tetractines, but monactine, triactine, and pentactine forms also occur. The monactines are tylostyle, the diactines centrotyle. The monactine and diactine rhabd-forms are 160-840 n long, and 13-29 n thick near the tyle. The tyle in the longer ones is often very large. The tri- to pentactines are 85-480 on an average 223.6 ju, in maximum diameter, and have rays 12-30 n thick at the base. The ends of the fully developed rays are always spiny. The same is the case in the rays reduced in length, provided the reduction has not gone too far. The rays reduced to mere knobs are smooth. The central parts of these spicules are usually smooth (Plate 94, figs. 24, 26, 28-33), more rarely covered with sparse small spines (Plate 94, figs. 25, 27). The acanthophores of the sponge used by the Palythoa to build its skeleton (Plate 94, figs. 14-23) are di- to pentactine. The diactines are not nearly so numerous among them as among the basal spicules from the sponge. The diactines are centrotyle, 170-400 /z long, and 20-30 /z thick near the central tyle. Among the tri- to pentactines, forms with two fully developed and one or two partly reduced rays are the most frequent. These spicules are 90- 260 /d in maximum diameter, very rarely as much as 350 /z, on an average 206.7 ^ , and their rays are 14-35 /z thick at the base, rarely up to 45 m- The average measurements of the tri- to pentactines of the sponge-body (223.6 u) and of the Palythoa (206.7 /z), given above, show that the former have on the whole a larger maximum diameter than the latter. Also the rhabd-forms show this, the average length of those of the sponge being considerably greater than of those of the Palythoa. Apart from this it is to be noted that the Paly- thoa spicules have stouter rays, and are more spiny than those of the sponge. These facts seem to indicate : — 1 , that the more slender and less spiny acantho- phores are young forms of the stouter and more spiny ones; 2, that none, or only a few, of these young spicules, but many of the old spicules, are shed by the sponge; and 3, that of the old, stouter, and more spiny spicules which are shed and thus placed at the disposal of the Palythoa, the latter selects the smaller (shorter) ones for building up its skeleton. HYALONEMA (OONEMA) CRASSIPINULUM. 337 The rays of the microhexactines (Plate 92, figs. 9-15) are usually nearly equal and all quite straight or nearly so. Only rarely microhexactines are found in which one or two of the rays are distinctly curved in their middle-part. The rays are 3.5-7 n thick at the base, conical, pointed, and covered with spines. The spines on the proximal half of the ray are sparse, vertical or slightly inclined towards the centre of the spicule, and up to 2 n long. The spines on the distal half are more numerous, smaller, and rather strongly inclined towards the centre of the spicule. Most of the microhexactines have rather long and slender rays. These spicules (Plate 92, figs. 9, 10) are 90-220 n in total diameter, and the basal thickness of their rays (3. 5-6. 5 m) is fairly in proportion to their size. Some microhexactines have much shorter and relatively much stouter rays. These spicules (Plate 92, fig. 11) are only 65-80 ^ in diameter, and have rays as much as 7 /j. thick at the base. The rare monadine microhexadine-derivates appear as strongly spined tylo- styles. They are about 130 /x long, and 8 n thick near the tyle. The terminal tyle itself is about 9 m in diameter. Morphologically four kinds of amphidiscs can be distinguished: — 1, large amphidiscs with fairly smooth shaft and broad and short anchors, about a third of the whole spicule in length; 2, medium amphidiscs with a stout smooth shaft and broad and long anchors, usually a little more than half the whole spicule in length; 3, medium amphidiscs with a slightly spined, rather slender shaft, and long, narrow anchors, more than a third of the whole spicule in length; and 4, small amphidiscs with slender, spined shaft and rather short anchors, only about a third of the whole spicule in length. The amphidiscs belonging to the first kind are 375-480 n long, those belong- ing to the second kind 110-200 /x, those belonging to the third kind 112-137 /x, and those belonging to the fourth kind 31-106 /x. The first and the fourth kinds are accordingly distinguished both morphologically and biometrically. The second and third kinds, although distinguished in the same manner from the first and fourth, are distinguished from each other morphologically only, and not biometrically. As the measurements given above and the adjoined graph show, the gap in the length frequency-curve separating the fourth from the second and third kinds is much narrower than that separating the second and third from the first kind. In spite of the width of this gap, and the entire absence of transi- tions between the second and third kinds of amphidiscs on the one hand and the first kind of amphidiscs on the other, I am inclined to combine the first, second, Length of Amphidiscs (/a). 338 HYALONEMA (OONEMA) CRASSIPINULUM. 01 Ol Number Fig. 21. — Amphidiscs. HYALONEMA (OONEMA) CRASSIPINULUM. 339 and third kinds, because in other closely allied species they are not so clearly separated biometrically. I distinguish accordingly two main groups of amphi- discs: — macramphidiscs 110-480 p long, and micramphidiscs 31-106 p long. The macramphidiscs comprise the first, second, and third kinds of amphi- discs. As shown above, the first kind is very clearly distinguished from the second and third both morphologically and biometrically. I therefore divide the macramphidiscs into two groups, large macramphidiscs 375-480 p long, and small macramphidiscs 110-200 p. The length frequency-curve of the large macramphidiscs has two distinct elevations. However, in view of the morphological similarity of the largest and the smallest, and the smallness of the number of large macramphidiscs observed and measured, I do not attach much importance to this, and consider the large macramphidiscs as a simple group. The length frequency-curve of the small macramphidiscs has a single elevation, and is remarkably regular biometrically. These spicules accord- ingly form a remarkably homogeneous group. Morphologically, however, two kinds of small macramphidiscs are to be distinguished : — those with relatively smaller, chiefly narrower anchors; and those with relatively larger, chiefly broader anchors. The micramphidiscs form morphologically a nearly continuous series, the smallest being connected by intermediate forms with the largest with hardly any break. Their length frequency-curve, however, shows four elevations and three depressions, one of which (at about 47.5 p) is rather conspicuous. In view of the slightness of the morphological differences between the micram- phidiscs to which the four elevations of the curve pertain, I abstain from sub- dividing them into subgroups corresponding to these elevations. Thus I distinguish four kinds of amphidiscs in this sponge: — large macram- phidiscs, small broad-anchored macramphidiscs, small narrow-anchored macram- phidiscs, and micramphidiscs. The large macramphidiscs (Plate 93, fig. 10) are very rare. In fact I found only seven in all, and although some of these were observed in the sections, it "is not impossible that they are foreign; the probability is, however, greatly in favor of their being proper to the sponge. These spicules are 375-480 p long, most frequently about 468 p. The shaft is cylindrical, 22-29 p thick, smooth, and slightly thickened in or near the centre. The terminal anchors are 168-215 p long, about a third of the whole spicule, and 210-260 p broad. The proportion of their length to their breadth is 110 to 107-155, on an average 100 : 340 HYALONEMA (OONEMA) CRASSIPINULUM. 129. The individual anchor-teeth are usually not curved quite uniformly, and pointed at the end. Their end-parts are parallel or slightly divergent. The broad-anchored small macramphidiscs (Plate 93, figs. 3-8; Plate 94, figs. 1-3) are very much rarer than in the allied species. They are 110-200 n long, and have a smooth cylindrical shaft 8-17 fx thick. Their anchors are 57-100 n long, usually 1-6 n more than half the whole spicule, and 58-172 n broad. The proportion of their length to their breadth is 100 to 101-179, on an average 100 : 144.6. It is to be noted that, the smaller of these spicules have relatively narrower anchors, the larger relatively broader anchors. Thus the proportion of anchor-length to anchor-breadth is in those under 130 ^ in length 100 to 101-148; in those over 180 n in length 100 to 150-179. The most fre- quent number of anchor-teeth is eight. The teeth of the two anchors of the same spicule are usually situated alternately (Plate 93, figs. 5, 7); sometimes, however, all the teeth, or at least some of them, lie opposite, and appear to be in contact with each other (Plate 93, fig. 3). The outer contour of the teeth usually at first slightly ascends. It is uniformly curved, concave to the shaft to within a short distance from the tip of the tooth, and abruptly bent inward at the end. The keel of the tooth extends as far as the curvature of the outer contour continues uniform. At the point of maximum breadth, which lies about two thirds of their length from their base, the teeth measure 22-31 \j in trans- verse diameter. Distally the teeth are slightly attenuated. The end is rounded. The narrow-anchored S7nall macramphidiscs (Plate 93, figs. 1, 2; Plate 94, fig. 4) are very rare. I observed only five of them, and it is possible that they are foreign. These spicules are 112-137 n long. The shaft is 5-7 n thick, slightly centrotyle, and roughened with indications of spines. The central t.yle is 1-3 n more in transverse diameter than the adjacent part of the shaft. The terminal anchors are usually shorter than half the length of the spicule, rarely a little longer. They are 52-70 n long and 52-59 n broad. The proportion of their length to their breadth is 100 to 84-104, on an average 100 : 95. The anchor- teeth are strongly curved in their basal part, but only slightly curved in their distal part. Some of these spicules have irregular anchors, composed of teeth unequal in length. The micramphidiscs (Plate 94, figs. 5-13), particularly the larger ones, are very abundant. They are 31-106 n long, most frequently about 84 n. The shaft is straight, centrotyle, and 1.5-4 n thick. The central tyle is 3. 5-5. 5 n in transverse diameter, that is 0.6-2. 6 n more than the adjacent parts of the shaft. An irregular verticil of spines, up to about 1 n long, arises from the HYALONEMA (OONEMA) DENSUM. 341 central tyle, and a good many similar spines are found also on other parts of the shaft. The spines are more abundant in the larger than in the smaller forms, and in some of the former (Plate 94, figs. 6, 7, 13) are remarkably numerous. The terminal anchors are 9-38 n long and 8-39 m broad. The proportion of their length to their breadth is 100 to 81-125, on an average 100 : 94. As stated above, the micramphidiscs of different sizes, are very similar in shape, the differ- ences in the proportions of their different dimensions being only slight. In the micramphidiscs over 80 n in length the proportion of anchor-length to anchor-breadth is 100 to 89-114, on an average 100 : 95, and the proportion of the anchor-length to the length of the whole spicule 1 to 2. 6-3. 2, on an average 1 : 2.9. In the micramphidiscs under 50 m in length the proportion of anchor-length to anchor-breadth is 100 to 78-125, on an average 100 : 90.5 ; and the proportion of the anchor-length to the length of the whole spicule 1 to 2.8-4, on an average 1 : 3.16. The curvature of the anchor-teeth decreases dis- tally. This decrease is more marked in the smaller than in the larger micram- phidiscs. The teeth are 4-7 ij. broad, and rounded at the end; their tips are usually nearly parallel. This sponge is obviously most closely allied to Hyalonema ( Oonevm ) sequoia. From this it differs by the absence of the smaller kind of small macramphidiscs with numerous anchor-teeth ; by the presence of narrow-anchored small macram- phidiscs, and superficial pinules with long strongly divergent spines on the proximal part of the distal ray; and by the smaller size of several kinds of its spicules, chiefly the superficial pinules. Hyalonema (Oonema) densum, sp. nov. Plate 94, figs. 34-42; Plate 95, figs. 1-20; Plate 96, figs. 1-14. One specimen of this species was trawled in the Eastern Tropical Pacific at Station 4649, on 10 November, 1904; 5° 17' S., 85° 19.5' W. ; depth 4086 m. (2235 f.); it grew on a bottom of sticky, gray mud; the bottom-temperature was 35.4°. The name has reference to the remarkable density of the sponge. Shape and size. The single specimen (Plate 95, fig. 4) appears as an inverted cone cut off obliquely and considerably extended at one side above. The upper portion protrudes on this side like a bulging rim for a distance of 8 mm. The sponge is 57 mm. high, and the regularly oval upper face 46 mm. long and 39 mm. broad. This upper face, which is to be considered as the gastral, is convex 342 HYALONEMA (OONEMA) DENSUM. and perforated by numerous broad-oval efferent apertures 0.2-0. 9 mm. wide (Plate 95, fig. 3). A pointed, very eccentrically situated gastral cone 8 mm. high and, at the base, 6 mm. thick arises from it. The conical body is slender and has no pores visible with the unaided eye. Its surface is to be considered as the dermal face of the sponge. Its lower end is torn off. The colour in spirit is dirty light brown. Canal-system. In the choanosome more or less radial canals, sometimes 0.8 mm. wide, are observed. Indications of elongate, perhaps tubular, flagellate chambers 30-70 ^ broad are observed in the sections. Skeleton. The whole of the surface is covered with a dense pinule-fur (Plate 95, figs. 1, 2). Between the proximal parts of the freely protruding distal rays of the pinules forming it are met small macramphidiscs, mostly with the shaft in a radial position. The dermal and gastral membranes are supported by the lateral rays of the superficial pinules, paratangential centro- tyle amphioxes, and the lateral rays of hypodermal or hypogastral pentactines. Masses of microhexactines and some small macramphidiscs occur in and just below these membranes. A good many large micramphidiscs, dense masses of microhexactines, and a few canalar pinules occur in the canal-walls. The micramphidiscs appear to be restricted to the efferent canals. Apart from these canalar spicules, one finds in the interior a few large macramphidiscs, hexactine megascleres, and small micramphidiscs, numerous ordinary small choanosomal amphioxes, and some large axial amphioxes forming the upper continuation of the stalk. In the lower part of the sponge-body numerous acanthophores are added to these spicules. These extend remarkably far up. The upper acanthophores have long, slender, and usually fairly straight and not very spiny rays. In the lower acanthophores the rays are either reduced in length, stout, and very spiny, or long, slender, not particularly spiny, and more or less, often considerably curved. The dermal pinules have a distal ray 230-855 m long. The length frequency- curve of their distal rays has a very marked depression at about 530 (x, and two perfectly distinct elevations at 370 and 650 n. I therefore distinguish two kinds of dermal pinules, a large and a small. The large dermal pinules (Plate 95, figs. 1, 15, 19, 20) are pentactine. Their distal ray is straight, 560-855 m long, most frequently about 650 n, and 12-23 m thick at the base. It ends with a short and stout terminal cone, and bears spines which extend quite down to its base, or nearly so. The lowest spines are very short, stout, conical, and vertical; distally the spines become larger and more HYALONEMA (OONEMA) DENSUM. 343 inclined and curved concave towards the tip of the ray. The largest spines usually attain a length of about 27 , u. The maximum diameter of the distal ray, together with the spines, is 32-85 /d. The lateral rays are 40-77 n long, nearly cylindrical in their proximal, and conical in their distal part. Their middle and sometimes also their proximal parts bear broad and low spines. The end-parts are smooth and sharply or bluntly pointed. The small dermal pinules are similar to the large ones. They are nearly always pentactine. Exceptionally a remnant of a proximal ray, sometimes 15 n long, is present. The distal ray is straight, 230-505 n long, most frequently about 370 n, and 6-10 ^ thick at the base. Its maximum diameter, together with the spines, is 12-47 n. The lateral rays are 40-68 n long. The gastral pinnies (Plate 95, figs. 2, 11-14, 16-18). Although the length frequency- curve of the distal rays of these spicules is irregular and exhibits no less than five elevations, these are separated by depressions so shallow that differently sized kinds of gastral pinules cannot be distinguished. The gastral pinules are generally pentactine, rarely hexactine. The hexactine forms are, however, not so rare among these pinules as among the dermal. Apart from this the gastral pinules are quite similar in shape to the dermal. The distal ray is straight, 300-930 n long, most frequently 400-650 n, and 10-28 n thick at the base. Its maximum thickness, together with the spines, is 25-80 n. The spines are sometimes 35 n long. The lateral rays (Plate 95, figs. 11, 12) are 35-82 n long. The proportion of the length of the distal to that of the lateral rays of the same spicule is 7-13 to 1, on an average 9:1. The proximal ray, when present, is, in shape and spinulation, similar to the laterals and 20- 68 m long. The scarce canalar pinules are mostly pentactine. The distal ray is 150- 200 /d long, and 7-10 n thick at the base. Its maximum transverse diameter, together with the spines, is 12-22 fi. The lateral rays are 50-60 y. long. The hypodermal and hypogastral pentactines are very similar. Both have a straight, conical, terminally rounded proximal ray 540-860 m long, and 20-48 n thick at the base. The lateral rays are also straight, conical, and rounded. Those of the same spicule are often very unequal in size. Their length is 250- 530 id. The hexactine megascleres are 1.1-3. 5 mm. long and 1.1-1. 8 mm. broad. In the larger, two opposite rays are longer than the other four. In the smaller the six rays are usually fairly equal in size. The rays are 40-90 n thick at the base, straight, generally regularly conical, and rounded at the end. Occasion- 3.44 HYALONEMA (OONEMA) DENSUM. ally the thickest part of the ray does not lie at its proximal end but farther out, some distance from the centre of the spicule. The largest hexactine observed was of this kind. In this spicule the two longer opposite rays measured 1.1 mm. and 2.4 mm. in length respectively. The longer of the two is 70 n thick at the base. Its point of maximum thickness is 0.4 mm. from the centre of the spicule, and here the ray measures 80 n in transverse diameter. At the rounded end it is 15 /x thick. In the proximal part of the ray the axial thread is simple and quite thin (0.5 n in diameter) ; distally it gradually increases in thickness to 5 m at the end of the ray. In its distal and middle-parts it is not simple but provided, at frequent intervals, with verticillate groups of strongly inclined branches with a maximum length of 15 m- The superficial and ordinary choanosomal amphioxes are centro tyle, usually 0.6-2. 2 mm. long, and 7-27 n thick near the middle. The central tyle, which not infrequently protrudes much more on one side of the spicule than on the other, is 13-37 n in transverse diameter, that is 1-18 n more than the adjacent parts of the spicule. The large axial amphioxes and rod-shaped fragments found in the central part of the sponge are 25-130 n thick. The largest intact one observed is a fusiform amphiox, blunt at both ends, 5 mm. long, and 28 n thick. The acanthophores (Plate 94, figs. 34-36) have from two to six, most fre- quently two or four rays. The dimensions of these spicules are tabulated below. ACANTHOPHORES. Number of rays more or less developed from higher up in the sponge from the lower end of the sponge total length (maximum diameter) of spicule x* basal thick- ness of rays total length (maximum diameter) of spicule basal thick- ness of rays M 2 620-1560 7-19 100-790 12-30 3 390-490 12-15 170-300 28 4 390-610 13-29 120-565 11-38 5 615 21 217-540 20-26 6 300-400 14-19 600 21 HYALONEMA (OONEMA) DENSUM. 345 The table shows that, apart from the few hexactine forms, which appear only partly to conform to the rule, the acanthophores situated farther up are larger and have more slender rays than those situated farther down. The rod- shaped diactine acanthophores are longer than any of the others. Apart from this the size (ray-length) of these spicules is by no means in inverse proportion to the ray-number; the triactines, for instance, are shorter than the tetractines. The thickest rays are met in the tetractines. This applies both to the upper and the lower tetractines. The diactines have a central and often also two ter- minal tyles. The latter sometimes attain remarkably large dimensions. In a spicule of this kind 780 ^ long and 15 n thick, the two terminal tyles were respectively 50 and 60 n in diameter. The small acanthophores are often spined throughout; in the large ones the spines are confined to the ends of the rays. The spines are low and broad, and attain 10 n in length and 16 n in breadth. They are conical and pointed or, more rarely, rounded at the end and dome- shaped. The acanthophores with rounded spines are characteristic of the spe- cies. The rays are straight or curved. Strongly curved rays are met particu- larly among the larger tri- to hexactines situated below. The rays of all the small acanthophores, of all the diactine acanthophores, and of all kinds of acanthophores situated farther up, are usually fairly straight. The microhexactines (Plate 94, figs. 37-40) are 60-165 n in diameter, usually 95-160 n. The rays are equal, conical, finely pointed, 3-6 m thick at the base, and curved slightly but quite distinctly and quite uniformly throughout their length. They bear spines which are rather sparse, vertical, and sometimes 1 n high in their proximal part, and which are more numerous, smaller, and directed backwards in their distal part. Toward the ends of the rays the spines decrease in size to such an extent that the end-parts themselves merely appear rough, even under the highest power. From a morphological point of view four kinds of amphidiscs can be dis- tinguished : — A, large ones, with broad, short anchors, less than a third of the whole spicule in length, and no protuberance, or only one or two, on the shaft; B, middle-sized ones with long and broad anchors, about half the length of the whole spicule; C, middle-sized ones with short elliptical anchors, about a third of the length of the whole spicule, and a shaft spined throughout; and D, small ones with short U-shaped anchors, less than a third of the whole spicule in length. The length frequency-curve of the amphidiscs, shown in Figure 22, exhibits four very distinct elevations separated by deep depressions or gaps. These 346 HYALONEMA (OONEMA) DENSUM. to o t\D cn CO o Number O 3 3 S' four elevations coincide with the four morphological groups above referred to. There can be no doubt, therefore, that we have here to deal with four distinct kinds of amphidiscs. The group A is very clearly distinguished from all the others, both morphologically and biometrically. The group B is clearly dis- tinguished morphologically from all other groups, but distinguished biometri- Macramphidiscs HYALONEMA (OONEMA) DENSUM. 347 cally by a wide gap in the length frequency-curve only from group A. Groups C and D differ morphologically greatly from A and B but not nearly so much from each other. Biometrically, that is judging from the width of the depres- sion separating the two elevations of the curve pertaining to them, they are also less clearly distinguished from each other than A is from B. Thus C and D together form a main group, which is to be named micramphi- discs, as it comprises the smallest amphidiscs. Although separated by a wide gap in the curve, and differing also morphologically, I am inclined to combine A and B in a like manner in one main group, which is to be named macramphi- discs, as it comprises the largest amphidiscs. Within each of these main groups I distinguish two subgroups differing in size, and thus divide the amphidiscs into the four groups: — large macramphidiscs (morphological group A); small macramphidiscs (morphological group B ); large micramphidiscs (morphologi- cal group C) ; and small micramphidiscs (morphological group D). The large macramphidiscs (Plate 96, figs. 8, 9, 14) are rare. They are 450-540 fi long, most frequently about 476 /x, and have a straight shaft, 21- 29 n thick. The shaft is either quite simple and cylindrical throughout (Plate 96, fig. 9), or it bears a rounded protuberance or two, about 10 n high, in its middle part (Plate 96, figs. 8, 14). The terminal anchors are 125-140 n long, less than a third of the whole spicule, and 190-230 n broad. The proportion of length to breadth of the anchors is 100 to 145-174, on an average 100 : 162. The anchors are composed of eight teeth. The individual teeth are throughout curved fairly uniformly and sharply pointed at the end. The small macramphidiscs (Plate 96, figs. 1-7, 10-13) are present in fair numbers, but are not nearly so abundant as in the allied species. They are 90- 184 n long, most frequently about 135.6 /x. The shaft is straight, simply cylin- drical, and 9-15 n thick. The terminal anchors are 45-92 n long, usually a little more than half the whole spicule. Their breadth is 60-136 /x. The proportion of anchor-length to anchor-breadth is 100 to 125-157, on an average 100 : 146.2. The anchors are usually composed of eight, more rarely of seven teeth. The teeth of the two anchors of the same spicule are usually situated so that those of the one anchor alternate regularly with those of the other. The individual teeth consist of an outer band-shaped part, up to 30 /x broad, and simply rounded at the end, and an inner keel, high at the base and uniformly narrowing dis- tally. The outer contour is more strongly curved in its proximal and distal than in its middle-parts. At the end of the tooth it is always strongly bent inwards. 348 HYALONEMA (OONEMA) DENSUM. The large micramphidiscs (Plate 95, figs. 5-8) are abundant. They are 44- 86 n long, most frequently about 69.5 m- The shaft is straight, centrotyle, and 1.5-4 n thick. The central tyle is 2-5 n in transverse diameter, that is 0.5-2. 5 n more than the adjacent parts of the shaft. The shaft bears rather numerous scattered spines, the largest of which arise from the central tyle. These spines are 1-4 n long and, if long, generally considerably curved. The terminal anchors are 13-31 n long, usually about a third of the whole spicule, and 15-35 n broad. The proportion of anchor-length to anchor-breadth is 100 to 78-123, on an aver- age 100 : 102.3. The individual teeth are curved rather strongly in their basal part. Distally the curvature decreases so that their ends are slightly divergent or nearly parallel. The small micramphidiscs (Plate 95, figs. 9, 10) are not numerous. They are 24-40 n long, most frequently about 26.8 n. The shaft is straight, usually distinctly centrotyle, and 1-1.7 n thick. The tyle is 1.5-2. 3 n in transverse diameter, that is 0.2-1. 2 n more than the adjacent parts of the shaft. The termi- nal anchors are 7-16.5 n long, usually less than a third of the whole spicule, and 7-14 n broad. The proportion of anchor-length to anchor-breadth is 100 to 75-143, on an average 100 : 97.8. The individual teeth arise vertically from the ends of the shaft, are straight in their basal part, curved through a quadrant in their middle-part, and straight again in their distal part. Their ends are parallel. Among the small micramphidiscs I found several irregular ones with asym- metric anchors. One of these is 16 n long, has a shaft 1.5 n thick, and possesses apparently only two teeth, one in each anchor. These two teeth stand opposite each other and are not very much shorter than the whole spicule, which is consequently similar to a depressed S. The nearest allies of the above sponge are the species Hyalonema ( Oonema ) sequoia, H. ( O .) crassipinulum, and II . (O.) henshawi described in this Report. From these it differs by the smaller size, and the distinct curvature of the rays of its micramphidiscs; by the possession of acanthophores with terminally rounded spines; by differences in the dimensions of its pinules; and by the shape and general density of its body. HYALONEMA (OONEMA) SEQUOIA. 349 Hyalonema (Oonema) sequoia, sp. nov. Plate 85, figs. 9-21; Plate 86, figs. 1-36; Plate 87, figs. 1-7; Plate 88, figs. 1-13; Plate 89, figs. 1-36; Plate 90, figs. 1-10; Plate 91, figs. 1-6. One specimen of this species was trawled in the Central Tropical Pacific, at Station 4740 on 11 February, 1905; 9° 2.1' S., 123° 20.1' W.; depth 4429 m. (2422 f.); it grew on a bottom of dark gray Globigerina ooze; the bottom- temperature was 34.2°. Most of its superficial pinules attain a very large size, exceeding the ordinary pinules of other hexactinellids in dimension as Sequoia gigantea does the other conifers. To this the name refers. Shape and size. The single specimen is much torn (Plate 86, fig. 8). It appears to be part of a wall, 4-6 mm. thick, of a wide tube or funnel. The specimen is without the stalk, and when laid down flat is 105 mm. long (high) and 116 mm. broad. A stalk, 84 mm. long and broken off at the end, arises from one end. The upper part of the specimen, that is the part opposite the stalk, is composed of lamellae, between the free margin of which remnants of reticulate pore-sieves are spread out. The colour in spirit is light brownish yellow. The skeleton. The pore-sieves (Plate 86, fig. 7) are supported by para- tangential amphioxes, most of which are small, but a few are large. The latter obviously correspond to the tignules of other hexactinellids. The pore-sieves also contain microhexactines and micramphidiscs. Numerous small macram- phidiscs and large pinules rest on the outer side of the amphioxes support- ing the strands of these reticulate sieves. Although now partly irregularly disposed (Plate 86, fig. 7), I do not doubt that, in life, the axes of the shafts of these small macramphidiscs and of the distal rays of the pinules were vertical to the surface. In the few places where the outer surface of the sponge is intact I found the same spicules, with the exception of the large amphioxes (tignules), and in addition hypodermal pentactines. Numerous slender amphioxes, some hexactine megascleres, masses of microhexactines, and a few large macramphi- discs have been observed in the choanosome of the upper and middle-parts of the body. In the spicule-preparations of these parts have been observed also pinule-like microhexactines, with one ray longer than the other five, and large numbers of micramphidiscs. The pinule-like microhexactines doubtlessly line the canal-walls. The position of the micramphidiscs may be the same. Acan- t.hophores with one to six stout and terminally interiorly spined rays occur in the basal part of the sponge-body, from which the stalk arises. The stalk con- sists of three thick and a number of slender spicules, all broken off distally. 350 HYALONEMA (OONEMA) SEQUOIA. Besides these spicules which will be described below, a number of others, chiefly amphidiscs (Plate 89, fig. 15e) and pinules, were found in the sponge. Since, however, some of these kinds of spicules are very rare, and since the other, more frequent ones are identical with spicules of Hyalonema ( Hyalonema ) agassizi and Hyalonema ( Prionema ) fimbriatum trawled at the same Station and contained in the same jar, I consider them as foreign. The superficial pinules (Plate 86, figs. 8, 13-26; Plate 87, figs. 1-7; Plate 88, figs. 7-13; Plate 89, fig. 15c) are nearly all pentactine, hexactine forms being very rare. These pinules are very unequal in size, the largest* attaining quite unusual dimensions. The distal ray is straight and 0.18-1.4 mm. long, most frequently about 0.9 mm. The length frequency-curve of the distal pinule-rays is simple, with a single elevation at 0.9 mm., which shows that these pinules form, in spite of their great dimensional differences, a simple, biometri- cally harmonious group. The distal ray is 5.5-55 ^ thick at the base, and together with the spines is 19-160 n thick at the thickest point. The maximum thickness is two to four times as great as the basal thickness. The point of maximum thickness lies rather far up, being usually three times as far from the base as from the tip of the ray. The distal ray ends in a terminal cone free from spines. This in the large pinules (Plate 87, figs. 3a, 5, 7; Plate 88, figs. 12a, 13a) is broad, rather blunt, and traversed by a remarkably thick axial thread; in the smaller (Plate 88, figs. 7-10, 11a) it is either stout or slender, and not infrequently sharp-pointed (Plate 88, fig. 10). In the large pinules the distal ray is covered with spines quite down to its base (Plate 87, fig. 3b; Plate 88, figs. 12b, 13b); in the smaller its basal part, for a short distance, is quite smooth (Plate 88, figs. 7-10, lib). The length of this smooth basal zone is, on the whole, in inverse proportion to the size of the spicule. The basal spines of the distal rays of the large pinules are short, broad, conic, sharp -pointed, and vertical. Distally they become more and more inclined towards the tip of the ray. At the same time they increase in length up to the point of maxi- mum thickness of the ray. From here up to the tip of the ray their length remains about the same. In typical large pinules the basal spines are up to 7 /j. long, and 10-14 ^ broad at the base. The upper spines are equally thick but attain 35 m in length. Most of the inclined spines on the upper and middle- parts of the ray extend longitudinally, in planes passing through the axis of the distal ray. In a good many of the large pinules, however, irregularities occur in the position of the spines. Either the spines on part of the ray are all spirally twisted and directed obliquely to one side (Plate 87, fig. 2), or there is, HYALONEMA (OONEMA) SEQUOIA. 351 somewhere near the tip, an umbilicus-like spot around which they are disposed quite irregularly (Plate 87, figs. 4-7). Very frequently a difference in the posi- tion of the spines on opposite sides is observed in the distal part of the ray, which renders it asymmetrical in appearance (Plate 87, fig. 3a; Plate 88, fig. 13a). These irregularities are so frequent that they can hardly be considered as abnormities. In some places the spines are isolated and irregularly scattered; in others they are arranged in spiral rows and appear to rise from the crests of scale-like protuberances of the central solid part of the ray. The lateral rays are conical, blunt, at the base slightly thinner than the distal ray, and 33-195 m long; they are usually one tenth to one third of the dis- tal ray in length. In the smaller pinules they are on the whole relatively much longer than in the larger ones. In the latter I have never found them more than a seventh of the distal ray in length. In the large pinules the lateral rays are spined more or less densely throughout their whole length. Their spines are vertical, and similar in shape and size to those on the basal part of the distal ray (Plate 87, fig. 3b; Plate 88, figs. 12b, 13b). The lateral rays of the smaller pinules are spined only in their distal part, and their spines are very small. The proximal ray of the rare hexactine superficial pinules is similar in shape and size to the laterals. The proximal rays measured are 57-95 m long. The hexactine megascleres (Plate 85, figs. 20, 21) have smooth, usually somewhat curved, rarely angularly bent, cylindroconical, terminally rounded rays. In the smaller forms the six rays are usually fairly equal in size, in the larger two opposite rays are generally considerably longer than the other four. The hexactine megascleres are usually 0.5-5. 5 mm. in maximum diameter, and their rays are 20-140 ^ thick at the base. But smaller forms with correspond- ingly thinner rays also occur. The hypodermal and hypogastral pentactines have a straight, cylindroconical, terminally rounded proximal ray, usually 0.5-1. 2 mm. long, ancl 20-40 n thick at the base. The lateral rays are much shorter, usually only 0.3-0. 6 mm. long. The amphioxes are of three kinds: — 1, small and slender, 2, small and stout, and 3, large. The small and slender amphioxes (Plate 89, fig. 15a), which predominate in the interior, are centrotyle, straight or curved, sometimes very considerably bent, usually 0.6-2 mm. long, and 6-20 ^ thick near the middle. The pro- portion of length to thickness is in these spicules 1000 : 7 to 1000 : 13. The central tyle is 10-21 ^ thick, that is 1-4 n more than the adjacent parts of the spicule. 352 HYALONEMA (OONEMA) SEQUOIA. The small and stout amphioxes (Plate 89, fig. 15b) are centrotyle, fairly straight, 0.6-2. 5 mm. long, and 22-70 n thick near the middle. The proportion of length to thickness is in these spicules 1000 : 17 to 1000 : 31. The central tyle is 24-75 /x thick, that is 1-7 /x more than the adjacent parts of the spicule. The large amphioxes ( tignules ) (Plate 89, figs. 1-5) are slightly and irregularly curved, not centrotyle, and not exactly cylindrical in the middle or uniformly thickened toward it; the outline is slightly wavy. They are 5-8 mm. long and 100-140 ijl thick. The proportion of length to thickness is in these spicules 1000 : 15 to 1000 : 20. The acanthophores (Plate 85, figs. 9-19) have one to six, most frequently four rays. The diactines are centrotyle. The forms with 5-6 rays are 140-224 m in maximum diameter and have rays 10-28 n thick, 3-4 “ “ 95-435 “ “ “ “ “ 2 “ “ 212-1050 “ long and near the central tyle 1 ray is 108-180 “ “ “ “ “ terminal tyle “ 15-36“ 14-18 “ 20-30 “ U U u The central tyle of the long diactines is usually 5-7 yu more in transverse diameter than the adjacent parts of the spicule. In the smaller tetractines the four rays are usually fairly equal; in the larger one ray, or two opposite rays, are often longer than the others. All the long-rayed (diactine) forms and a few of the short-rayed (mon- to hexactine) ones have rays smooth in their proxi- mal and middle-parts and spined only in their end-parts. Most of the mon- to hexactine forms are spined throughout, the terminal spines being, as a rule, considerably larger than the more proximal ones. The spines are vertical, broad, low, conical, and pointed. The stalk-spicules are all broken off at the distal end. The parts present have a maximum thickness of 0.2- 1.2 mm. The microhex actines (Plate 86, figs. 9, 11, 12, 35, 36; Plate 88, figs. 1-4) are 60-200 \x in diameter, generally 95-170 /x, and have equal, regularly arranged rays. The rays are perfectly straight, 4-6 /j. thick at the base, conical, and sharp- pointed. Everywhere except at the extreme tip they bear spines. The spines on their proximal half arise vertically; beyond that they incline more and more backward, towards the centrum of the spicule. The largest spines are those arising at a distance of about a third of the length of the ray from the centrum. Here they are about 1.5 jx long, and from here they decrease in size, both distally and proximally. HYALONEMA (OONEMA) SEQUOIA. 353 In the centrifuge spicule-preparations (Plate 86, fig. 10) I found a few monac- tine microhexactine-derivates. This spicule appears as a tylostyle and is spined throughout. Its dimensions are: — length 167 n, basal thickness of ray 6 fi, diameter of tyle 9 /x- The true choanosomal microhexactines have, as above stated, equal rays. In the spicule-preparations, however, a large number of small spined hexactines are found, in which one ray is considerably larger than the other five. These spicules I consider as pinule-like derivates of the regular microhexactines, which line the canal-walls, and are therefore to be considered as canalaria. These pinule-like microhexactine-derivate canalaria (Plate 88, figs. 5, 6) have a longer (distal) ray, 1 15-300 n long, and 5-11 m thick at the base, and five shorter (proximal and lateral) rays, 40-95 n long. The proximal ray may be longer or slightly shorter than the laterals. All the rays are spined. The spines on the distal ray are longer than the spines on the other rays — the more so, the more the distal exceeds the other rays in length. They are also for the most part directed obliquely upwards towards the tip of the ray. The amphidiscs. Morphologically two main kinds of amphidiscs can be distinguished: — amphidiscs with broad terminal anchors and a shaft which is either quite smooth or provided only with one or a few terminally rounded protuberances or spines, and amphidiscs with slender terminal anchors and generally spiny shaft. The former are large, 90-550 /x long; the latter are small, 17.5-122 ^ long. I consider the former as macramphidiscs, the latter as micramphidiscs. Among the macramphidiscs two subgroups can be distinguished both morphologically and biometrically. In one the anchors are much shorter than half the length of the whole spicule, and the anchor-teeth pointed; in the other the anchors are about half as long as the whole spicule, and the anchor- teeth terminally rounded. The former are larger, 370-550 m long; the latter smaller, 90-195 ^ long. The differences in their anchors, and the absence of intermediate forms between 195 and 370 n in length, which finds its expres- sion in a wide gap in the length frequency-curve, Figure 23, very clearly distinguish these two kinds of macramphidiscs from each other. 1 accord- ingly divide the macramphidiscs into two subgroups: — large and small macramphidiscs. The length frequency-curve of the micramphidiscs also shows a great depression, which lies at about 57 /x and reaches down to the 0-line. Thus also among these spicules a larger and a smaller kind can be distinguished. The 354 HYALONEMA (OONEMA) SEQUOIA. larger ones, to which the part of the curve to the right of this depression refers, and which are 63-122 /x long, have anchor-teeth distally rather divergent. The smaller ones, to which the part of the curve to the left of the depression refers, and which are 17.5-52 /x long, have anchor-teeth distally nearly parallel. I therefore also divide the micramphidiscs into two subgroups : — large and small micram- phidiscs. It is to be noted that these two kinds of micramphidiscs do not differ so much from each other as the two kinds of macramphidiscs. I distin- CO 3 "O nr cl a *0 nr Fig. 23. — Amphidiscs. HYALONEMA (OONEMA) SEQUOIA. 355 guish four kinds of amphidiscs in this sponge: — 1, large macramphidiscs, 2, small macramphidiscs, 3, large micramphidiscs, and 4, small micramphidiscs. Although the length frequency-curve of the large macramphidiscs has two summits, I do not distinguish two distinct groups among these spicules, because the depression between the two summits is but slight and because there are no notable morphological differences between the spicules to which the two parts of the curve on each side of the depression refer. The large macramphidiscs (Plate 86, figs. 1-6; Plate 89, figs. 31, 32; Plate 91, figs. 1-6) are 370-550 m long, most frequently about 425 /z. The shaft is straight, cylindrical, and 19-27 n thick. It usually bears a few broad and low quite insignificant tubercles. Some of these are often arranged in an irregular verticil situated in the middle-part of the shaft, which is, at this point, usually slightly thickened to an inconspicuous central tyle, only 1-3 /x, exceptionally as much as 6 /x, more than the adjacent parts in transverse diameter. Rarely the shaft bears a larger, cylindrical, terminally rounded spine, sometimes 28 /z long, and 10 m thick (Plate 86, fig. 4). I have never observed more than one such spine on the shaft of the large macramphidiscs. The terminal anchors are 120-170 /x long and 200-256 /x broad. The proportion of their length to their breadth is 100 : 139 to 100 : 196, on an average 100 : 171.3. The proportion of the anchor-length to the total length of the spicule is 1 to 2. 6-4. 7, on an average 1 : 3.6. The anchors are usually composed of eight teeth. The teeth of the two anchors of the same spicule lie opposite each other in the same planes passing through the axis of the shaft. The indi- vidual teeth are about 25 /z broad near the base, and pointed at the end (Plate 89, figs. 31, 32). Their curvature is usually greater at the base and at the end than in the middle. The tip of the tooth is sometimes abruptly bent either inward (Plate 91, fig. 4) or, more rarely, outward (Plate 91, fig. 1). The teeth occasionally bear conspicuous, somewhat branch-like protuberances on their convex outer (Plate 91, fig. 3) or concave inner side (Plate 91, fig. 2). A well- marked depression can be made out, sometimes very clearly, on the apex of the anchor (Plate 91, fig. 4). The length frequency-curve of the small macramphidiscs has two summits separated by a rather conspicuous gap. The smaller ones, to which the part of the curve to the left of the depression refers, have a larger number of anchor- teeth than the larger ones, to which the part of the curve to the right of the depression refers. Two kinds of small macramphidiscs could therefore be distinguished. Since, however, the differences between them are not great and 356 HYALONEMA (OONEMA) SEQUOIA. since the extreme forms are connected by numerous transitions, I shall here describe both together. The small macramphidiscs (Plate 86, figs. 7, 27-34; Plate 89, fig. 15d; Plate 90, figs. 1-10) are 90-195 /u long, most frequently about 164 /x. The shaft is straight, smooth, cylindrical, and 5.5-16.5 /x thick. The terminal anchors are 39-100 /x long, and 55-174 /i broad, usually 70-150 /jl. The pro- portion of anchor-length to anchor-breadth is 100 : 120 to 100 : 178, on an average 100 : 149. As has been stated above, these anchors are about half as long as the whole spicule, sometimes a little shorter than that, more frequently a little longer. Each anchor is composed of five to thirteen teeth. The larger amphidiscs of this kind, that is those to which the part of the length frequency- curve culminating at 164 n refers, have five to ten, usually eight teeth; the smaller, to which the part of the curve culminating at 93 /x refers, have eight to thirteen, usually eleven teeth. The two terminal anchors of the same spicule are composed of the same number of teeth. The teeth of the terminal anchors extend in planes passing through the axis of the spicule. The anchor-teeth planes of one anchor enclose equal angles with their neighbours, each 360 degrees divided by the number of teeth. The anchor-teeth planes of the other anchor of the same spicule alternate regularly with these in such manner that they divide each angle into two equal parts (halves). Thus the tips of the teeth of the two opposite anchors are not opposite but alternate. The individual anchor-teeth are curved, either uniformly or, more fre- quently, less in the middle-part than at the base and at the tip. The outer contour of each tooth is abruptly curved inwards at the distal end. The teeth are T-shaped in transverse section. Their outer (upper) part, which corresponds to the upper stroke of the T, has the shape of a curved band increasing in breadth distally to a point three quarters of the length of the tooth from its base. Here . the tooth is 9-30 /x broad. The end-part of the tooth, lying beyond this point of maximum breadth, is simply rounded (Plate 90, figs. 1, 3, 7, 9). The inner (lower) part of the tooth, which corresponds to the lower stroke of the T, is a thick keel, uniformly decreasing in height distally. The end-part of the upper (outer) band-shaped portion of the tooth bends down around the end-part of the keel on all sides except the axial, so that, viewed in profile, the end-part of the whole tooth becomes strikingly similar to a crow’s beak (Plate 90, figs. 4, 6, 8, 10). Slightly abnorrnal s?nall macramphidiscs with one or more somewhat irregu- lar teeth, like the one represented (Plate 90, figs. 5, 6), have repeatedly been met. HYALONEMA (OONEMA) SEQUOIA. 357 More strongly aberrant forms are much rarer. A small macramphidisc of this kind (Plate 89, figs. 35, 36) is 112 /x long, and has a shaft 14 n thick. The termi- nal anchors are very irregular, spirally twisted, and on one side much longer than on the other. The chords of the longest anchor-teeth are more than three quarters of the whole spicule in length. The length frequency-curve of the large micramphidiscs also has two summits, but as the depression separating them is slight, and as the spicules to which the two parts of the curve on the two sides of it refer, are very similar in shape, I do not consider this irregularity of the length frequency-curve sufficient for dividing the large micramphidiscs into two groups. The large micramphidiscs (Plate 89, figs. 6-14) are 63-122 n long, most frequently about 93 /x. The shaft is 2.5-4 /x thick, and generally thickened in its middle-part to a central tyle 5-6 m in diameter. Rarely it is of uniform thick- ness throughout and without a tyle. With the exception of its end-parts, which are smooth, the whole of the shaft is covered with spines. The spines arising from the tyle are usually arranged in an irregular oblique verticil. These spines are larger than the others. The terminal anchors are 29-43 /x long and 25-40 n broad. The proportion of their length to their breadth is 100 : 75 to 100 : 105, on an average 100 : 87.9. The proportion of the anchor-length to the length of the whole spicule is 1 to 2.4-3. 6, on an average 1 : 2.7. The individual anchor- teeth are curved strongly at the base, but curved only slightly in their middle- part. The tip of the tooth is frequently abruptly bent inwards. Apart from this abruptly bent end-part, the distal half of the tooth diverges from the shaft at an angle of 6°-12°. I found an abnormal large micramphidisc with strongly reduced terminal anchors. This spicule (Plate 89, figs. 16-19) is 100 n long. Its shaft is straight, 8 /x thick, and covered with numerous scattered tubercles and a verticil of short, stout, cylindrical, terminally rounded spines. The terminal anchors are rudi- mentary, only 17 /x long and 23 /x broad, and composed of a terminal tyle enclosed by thin leaf-like teeth, most of which terminate with two terminal spines. The length frequency-curve of the small micramphidiscs has three sum- mits. The two depressions separating them are inconsiderable, and the small micramphidiscs of different sizes differ only in that the smallest generally have a smooth shaft, the larger generally a spiny one. Although the smallest of these amphidiscs, belonging to the elevation of the curve to the extreme left, might therefore be separated from the others, I think it best to consider them all as forming a single group, and describe them together. 358 HYALONEMA (PHI ALONEMA ) BREVANCORA. The small micramphidiscs (Plate 89, figs. 20-30, 34) are 17.5-52 ^ long, most frequently about 32.5 The shaft is 0.8-2 n thick, and thickened in the middle-part to a central tyle 2-3.3 n in transverse diameter, that is 0.5-1. 3 n more than the adjacent parts of the shaft. In most of the larger and some of the smaller forms the shaft is spined. In most of the small and a few of the larger it is smooth. The terminal anchors are 5-20 m long and 5.5-15 n broad. The proportion of anchor-length to anchor-breadth is 100 : 75 to 100 : 110, on an average 100 : 90. The proportion of the anchor-length to the total length of the spicule is 1 to 2. 5-4. 5, on an average 1 : 3.1. The anchor-teeth are strongly curved in their proximal and nearly straight in their distal part. Their straight distal parts are slightly divergent, or nearly parallel to the shaft. The nearest allies of this sponge are Hyalonema ( Oonema ) henshawi, H. (0.) densum, and II. (O.) crassipinylum. From all of them it differs by its super- ficial pinules attaining a much larger size; H. (0.) densum is further distinguished from it by having slightly curved microhexactine rays; H. (O.) henshawi by apparently being destitute of the large macramphi discs; and II. ( O .) crassi- pinulum by having smaller spicules, by being destitute of the smaller small macramphidiscs with numerous anchor-teeth, and by possessing small narrow- anchored macramphidiscs and pinules with large, strongly divergent spines on the proximal part of the distal ray. PHIALONEMA, subgen. nov. Species of Hyalonema, whose amphidiscs of one kind (the largest) have small, very short, and relatively broad terminal anchors. The collection contains four specimens and two fragments of this sub- genus. These belong to two species, one of which is new. Hyalonema (Phialonema) brevancora, sp. nov. Plate 55, figs. 1-37. There are in the collection two fragments of this species, both from the Central Tropical Pacific, Station 3684 (A.A. 17), on 10 September, 1899; 0° 50' N., 137° 54' W. ; depth 4504 m. (2463 f.); they grew on a bottom of light yellow-gray Globigerina ooze. The large macramphidiscs have small, particularly low terminal anchors. To this the name refers. HYALONEMA (PHIALONEMA) BREVANCORA. 359 Shape and size. The larger fragment (Plate 55, fig. 1) is an irregular, porous, flattened mass measuring 47 by 38 by 8 mm. The smaller one is only 22 mm. long. The colour in spirit is dirty white. The skeleton consists of pinules; hexactine, pentactine, and rhabd mega- scleres; microhexactines; and amphidiscs. In most of the pinules in the preparation the distal ray bears relatively very long spines; these pinules are probably hypodermal or hypogastral. In some pinules these spines are very short; these may be canalar. The hexactine megascleres are found in the innermost part of the specimens; the pentactines are no doubt hypodermal or hypogastral. The rhabd megascleres for the most part form bundles. The microhexactines are numerous, and all of the same kind. Macramphidiscs and large and small micramphidiscs can be distinguished among the amphidiscs. The small micramphidiscs are abundant, the other amphidisc-forms rare. The (probably dermal and gast.ral) pinules with long-spined distal ray (Plate 65, figs. 19-28, 30, 32, 33) are nearly always pentactine, very rarely hexactine. The distal ray is straight, 70-89 n long, and 3-4 n thick at the base. It bears spines along its whole length. The spines on the proximal third or so of its length are very small, straight, and directed obliquely upwards. The distal and middle-parts of the ray are covered with spines very unequal in length and in curvature, the large and the small ones being here irregularly intermingled (Plate 55, fig. 19). Some of these spines attain a relatively very considerable size, the largest being 18-54 n long and about 2 ^ thick at the base. The lower spines, both large and small, are usually nearly straight, and very divergent (Plate 55, figs. 22, 25, 28). Farther up the short spines only are like this, most of the longer ones being curved, concave to the ray. This curva- ture is not infrequently so great that their ends become inclined towards the distal part of the ray (Plate 55, figs. 19, 21, 23). The spines are conic and sharp- pointed. Some of the larger ones bear one or two, rarely more, secondary spine- lets, usually 2-3 m long, and inclined towards the end of the spines from which they arise. The maximum thickness of the distal ray, together with the spines, generally is 22-37 /x, rarely as much as 54 fx. The lateral rays are usually 22-37 /x long, sometimes longer. They are cylindrical proximally, conic clistally, pointed, and beset with numerous oblique spines inclined towards the end of the ray. These spines attain a very considerable size, particularly in the distal and middle-parts of the ray. The lateral spines of these rays seem to be larger than the others; they give to the contour of the ray, when seen from above, a markedly 360 HYALONEMA (PHIALONEMA) BREVANCORA. serrated appearance (Plate 55, figs. 32, 33). The proximal ray, when present, is similar to the laterals, and attains a length of 27 n (Plate 55, fig. 30). The (probably canalar) pinules with short-spined distal raiy (Plate 55, fig. 29) observed by me were all pentactines. The distal ray is 66-85 n long, and about 5 m thick at the base. Its spines are straight, conic, small, and directed obliquely upwards towards the tip of the ray. They are largest in the middle of the ray and decrease in size both distally and proximally. The distal end-part of the ray is often, for a considerable distance, quite free from spines. The maximum diameter of the distal ray, together with the spines, is usually about 14 /x. The lateral rays are pointed, spiny, and usually 28-45 n long. The pentactine megascleres (Plate 55, figs. 2, 3) have straight, conic rays, 20-40 m thick at the base, and rounded at the end. The proximal ray is usu- ally 0. 8-1.1 mm. long; the laterals are 0.25-0.6 mm. long, and slightly inclined towards the proximal, with which they enclose angles of 78°-84°. The hexactine megascleres (Plate 55, fig. 31) observed measured 0.4-0. 9 mm. in diameter, and had somewhat unequal, straight, conic, and blunt rays 7-16 m thick at the base. The rhabd megascleres (Plate 55, figs. 4, 6) observed are for the most part more or less curved centrotyle amphioxes. These spicules are 0.4-4. 5 mm. long and 4-20 /x thick near the centre. The proportion of the thickness of the spicule to the diameter of the tyle is 100 : 125 to 100 : 225, most frequently about 100 : 150. There are besides, these spicules cent.rotjde amphioxes angu- larly bent in the middle (Plate 55, fig. 4) and centrotyle rhabds with one of the actines reduced in length and thickened at the end to a terminal tyle. In some of the latter a kind of terminal spine arises, from the thickened end (Plate 55, fig. 6). The microhexactines (Plate 55, figs. 34, 37) measure 85-184 n in diameter, most frequently about 150 m, and have six equal, perfectly straight, conic, sharp-pointed rays, usually 2-3 /x thick at the base. The rays bear oblique, outwardly directed spines. These are numerous and very small, usually under 0.5 m in length. Of amphidiscs three kinds are to be distinguished: — macramphidiscs, large micramphidiscs, and small micramphidiscs. The 7nacramphidiscs (Plate 55, figs. 5, 14-18) are 285-349 m long, most fre- quently about 315 /j,. The shaft is straight and near the centre, where it is thinnest, 6-9 m in transverse diameter. It is generally thickened abruptly in the middle to a central tyle 10-13 n in diameter. Toward the ends it is always HYALONEMA (PHIALONEMA) BREV ANGORA. 361 gradually thickened to about double its minimum thickness near the middle. The central thickening bears a verticil of conic, truncate spines, 5-10 n long, and 3-4 n thick at the base. The truncate ends of these spines bear clusters of very minute, short, secondary spinelets. One of the large macramphidiscs observed was destitute alike of the central tyle and the central spine-verticil. Apart from this spine- verticil, the shaft is, in all the large macramphidiscs observed, entirely smooth. The terminal anchors are 25-41 n long, about a tenth of the whole spicule, and 5.3-72 /* broad. The proportion of the length to the breadth of these anchors is 100 : 145 to 100 : 240, on an average 100 : 203. The anchor usually consists of eight teeth. The individual teeth are either uniformly curved, concave to the shaft throughout, or thus curved only in their basal and middle-part, and abruptly bent down at the end. The end-parts of the teeth enclose angles of about 25° with the axis of the shaft. The basal parts of the teeth appear to be massive; distally they thin out to rounded, spoon-like lamellae about 15 m broad. The micramphidiscs range from 18 to 38 i± in length. In the frequency- curve pertaining to this dimension there is a marked depression at about 33 n- The micramphidiscs shorter than this have, as a rule, nearly smooth shafts; those as large or larger than this, very spiny shafts. I consider the former as small, the latter as large micramphidiscs. The large micramphidiscs (Plate 55, figs. 10-12) are 33-38 m long, most frequently about 36 ,u. The shaft is cylindrical, 1.6-1. 8 /z thick, and covered with numerous irregularly scattered spines. The terminal anchors are 7-11 n long, a sixth to a fourth of the whole spicule, and 8-10.5 m broad. The propor- tion of anchor-length to anchor-breadth is 100 : 90 to 100 : 114, on an average 100 : 104. The individual teeth are rather strongly and uniformly curved in their basal part; distally the radius of curvature increases. Their nearly straight end-parts are approximately parallel to the shaft. The small micramphidiscs (Plate 55, figs. 7-9, 13) are 18-32 /z long, most frequently about 26 /z. The shaft is straight, cylindrical, and 1.2-1. 6 ^ thick. It is smooth, or bears a few small spines in its middle-part. The anchors are 4-8 /z long, a sixth to nearly a third of the whole spicule, and 7-9.5 n broad. The proportion of anchor-length to anchor-breadth is 100 : 100 to 100 : 180, on an average 100 : 131. The anchor-teeth of the small micramphidiscs are, in respect to their curvature, similar to those of the large micramphidiscs above described. Although the fragmentary condition of the specimens renders it difficult to decide to which genus of Amphidiscophora they belong, the probability is 362 HYALONEMA (PHIALONEMA) PATERIFERUM. that, they are Hyalonemas, and if so they must be placed in the subgenus Phialonema. Of the known species of Hyalonema H. globus F. E. Schulze 1 appears to be most nearly allied to the sponges above described. With this species they agree fairly well in respect to the pinules, the shape of the shaft, and the short- ness and breadth of the anchor-teeth of the large macramphidiscs. They differ, however, from H. globus by having secondary spinelets on some of the primary spines of the distal rays of their pinules, by their small micramphidiscs being much larger and by the anchors of their large macramphidiscs having an alto- gether different shape. Hyalonema (Phialonema) pateriferum Wilson. Plate 50, figs. 6-15; Plate 51, figs. 1-28; Plate 52, figs. 1-29. Mem. M. C. Z., 1904, 30, p. 28, Plate 1, figs. 1-13. Six specimens of this species were collected during the expeditions of 1899- 1900 and 1904-1905 in the Central and Eastern parts of the Tropical Pacific. Two of these, found at Station 3684 (A. A. 17), together with two other specimens and three fragments of the same species previously collected in the Gulf of Panama at Stations 3363 and 3376, were described by Wilson as Hyalonema pateriferum. Among the sponges of the expeditions of 1899-1900 and 1904- 1905 placed at my disposal for description, there are four specimens, all from different stations, which belong to this species. Two of these were trawled off the coast of northern Peru at Stations 4651 and 4656, and two in the Eastern Tropical Pacific at Stations 4721 and 4742. For the reasons given below I distinguish six forms within this species: — the two specimens and three fragments described by Wilson from Stations 3363 and 3376 A the two specimens described by Wilson from Station 3684 (A. A. 17) B the specimen examined by me from Station 4651 C the specimen examined by me from Station 4656 D the specimen examined by me from Station 4721 E and the specimen examined by me from Station 4742 F Shape and size. One of the specimens of form A is, according to Wilson (loc. cit.), obconical, irregular, 65 mm. high, 90 mm. broad, and provided with a F. E. Schulze. Rept. Voy. Challenger, 1887, 21, p. 221, pi. 40, figs. 1-16. HYALONEMA (PHIALONEMA) P ATE R I FE RUM . 363 stalk 330 mm. long, and 6 mm. thick at the base. Another is saucer-shaped, 40 mm. deep, 85 mm. long, and 65 mm. broad. The dermal membrane and the central part of the gastral membrane are reticulate. The marginal part of the latter is perforated by efferent pores 1.5 mm. wide. The specimens of form B are, according to the same author ( loc . cit.), flattened. One is saucer-shaped, 15 mm. deep, 80 mm. long, and 60 mm. broad; the other a fragment, probably of a similar sponge. The surface is continuous and smooth, not reticulate. The specimen of form C (Plate 52, fig. 20) appears as a broad and low, conic cup. It is 52 mm. high, 61 mm. long, and 54 mm. broad. The central part of the cup-wall is very thick. Distally it thins out to a sharp margin. The lower truncate end, from which in life the stalk probably arose, is lacerated. No trace of a stalk or a gastral cone can now be detected in the specimen. The outer (dermal) surface of the cup-wall is much damaged, and appears irregular and very porous. The inner (gastral) surface is, for a considerable extent, still covered by the gastral membrane. This is perforated by rather large broad- oval apertures. The specimen of form D (Plate 52, fig. 21) is a slightly curved lamella with rounded margin, 45 mm. long, 36 mm. broad, and uniformly 10 mm. thick. The larger part of the surface is smooth. On the concave (gastral) face the superficial (gastral) membrane is preserved. There is no gastral cone. A portion of the margin of the sponge is much lacerated. From this part the now missing stalk probably arose. The specimen of form E (Plate 51, fig. 1) is a porous, lacerated, lamellar fragment, and measures 60 by 32 by 8 mm. The specimen of form F is likewise very fragmentary. It appears as an irregular, porous lamella and measures 33 by 29 by 4 mm. The colour of the specimens of forms C and D in spirit is brown with a greenish tinge, that of form E reddish brown, and that of form F whitish. Canal-system. The efferent canal-systems are, according to Wilson (loc. cit.), in form A 5-10 mm. wide, and traceable quite down to the basal part of the sponge. In form D the flagellate chambers appear to be elongated, sac-shaped, irregularly curved, and 70-90 m broad. The skeleton. The surface of the body is covered with a dense pinule-fur (Plate 52, figs. 22, 23). In the forms A and B examined by Wilson (loc. cit.) the fur of the dermal face is composed of pinnies with distal rays of moderate and fairly equal length. On the gastral face pinules with much longer distal rays lie scattered between the masses of pinules with moderately long distal rays. In the forms C and D, pinules with long distal rays are scattered among the ordi- nary ones also in the fur of the dermal face. So far as the fragmentary state 364 HYALONEMA (PHIALONEMA) PATERIFERUM. of the specimens allows one to judge, this is also the case in the forms E and F. It is certainly true in some forms, probably in all, that from the margins which mark the boundary between the dermal and the gastral faces there arise centro- tyle amphioxes, diactine pinnies, and spicules transitional between these forms. Besides the lateral rays of the pi nules, amphidiscs, paratangentially extending centrotyle amphioxes, and the lateral rays of pentactine megascleres are found in the dermal and gastral membranes. According to Wilson ( loc . cit.) the amphi- discs of the superficial membranes are large macramphidiscs, and he says that these spicules are very abundant in these membranes of the forms ( A and B) studied by him. In the specimens of forms D and E, examined by me, where the superficial membranes are more or less preserved, I found them occupied by micramphidiscs in places very abundant, but nearly destitute of macram- phidiscs. Below the superficial membranes, the apical (proximal rays of the pentactines, centrotyle amphioxes, and a few transitions between them and diac- tine pinnies, occur. All these spicules (spicule-rays) are situated radially. Hexactine megascleres, canalar pinules, microhexactines, transitions between these and the pinules, and amphidiscs are met in the interior of the body rhabds, which are, for the most part, centrotyle amphioxes. In the vicinity of the point of origin of the stalk stout-rayed acanthophores occur. Many of the rhabds of the interior form bundles which traverse the choanosome. The hexactine megascleres appear to increase in size toward the central part of the sponge. In the forms C, D, E, and F the canalar pinules are scarce, and irregularly and sparsely scattered over the walls of some of the canals only, the walls of other canals appearing to be destitute of these spicules. The microhexactines vary considerably in respect to their size, their spinulation, and the curvature of their rays. Wilson {loc. cit.) considers the large, straight-rayed, and strongly spined ones (in the forms A and B) as canalaria. In the forms D, E, and F these spicules do not appear to be restricted to the canal-walls. In form C I failed to find any of the large, straighter-rayed microhexactines. The hexactine and pentactine transitions between the microhexactines and the pinules are, in the forms D, E , and F true canalaria. The amphidiscs, among which four forms can be distinguished, are exceedingly abundant. Micramphidiscs, chiefly large ones, clothe the walls of the efferent canals of form D in dense masses. In the forms C, D, E, and F macramphidiscs are scattered in very large numbers through the choanosome. According to Wilson (loc. cit.) only few macramphi- discs occur in the interior of forms A and B. The large macramphidiscs are much more numerous than the small ones. The stout-rayed acanthophores HYALONEMA (PHIALONEMA) PATERIFERUM. 365 were chiefly observed by Wilson ( loc . cit.) in one of the specimens of form A, and by me in the specimen of form F. They probably occur in equal abundance also in the others, and in all they envelop the parts of the stalk-spicules lying just below the surface, within the body of the sponge. The stalk is preserved only in one of the specimens of form A. It consists here, according to Wilson (loc. cit.), of about fifty spicules, broken off below. The marginal pillules are diactine; the dermal, gastral, and canalar mostly pentactine, more rarely hexactine, and still more rarely diactine. I was unable to find any marked difference between the dermal, gastral, and canalar pinules. The slight difference in the length of the distal ray of the canalar and the other pinules, noticed by Wilson (loc. cit.) in the forms A and B, is not pronounced in the forms examined by me. I shall, therefore, in describing the pinules, not take their position into account. By far the most frequent form of pinule is a pentactine with rays of moderate length. In the other, much less frequent forms, a sixth (proximal) ray is devel- oped, or the distal or lateral rays are elongated, or the latter reduced to mere rounded knobs. The pentactine (and hexactine) pinules are connected by trans- itions with each other and with the large straight-rayed microhexactines. The pinules with well-developed proximal and reduced lateral rays appear as diac- tines. These are connected by transitional forms with the centrotyle amphioxes but hardly at all with the other pinule-forms. The pentactine or (rarely) hexactine pinules with a distal ray of moderate length (Plate 50, figs. 6-8; Plate 52, figs. 11-14) and well-developed laterals have a conical distal ray, very gradually attenuated to an exceedingly slender and sharp-pointed terminal cone. The distal ray is, in the pinules with moderate laterals, generally straight; in those with long laterals, which usually also have a long sixth proximal, and which appear as transitions to the microhexactines, often curved. The basal and terminal parts of the distal ray are smooth ; its central part bears small spines. The distal spines are always rather strongly inclined towards the tip of the ray. The proximal spines are either also so inclined (Plate 50, figs. 6-8), or more divergent, often even vertical, or inclined slightly in the opposite direction (Plate 52, figs. 11-13). The distal ray is in forms A and B, according to Wilson (loc. cit.), 100-220 m long, in form C 65-217 n, in form D 85-240 n, in form E 85-137 m, and in form F 93-220 yu. The basal and maximum thicknesses (together with the spines) of the distal ray are in forms A and B, according to Wilson (loc. cit.), base 5m, maximum?; in form C base 3-5 m, maximum 7-20 n; in form D base 2.5-5 n, maximum 3-22 m ; in form E 366 HYALONEMA (PHI ALONEM A) PATE RIFERUM. base 4-6 n, maximum 8-27 n; and in form F base 3.5-6 fi, maximum 7-16 n. The maximum thickness of the distal ray, together with the spines, is in the ordinary pinules with laterals of moderate length usually 8-16 n; distal rays with a maximum thickness of only 6 n or less are found only among those forms with long laterals, which pass into the microhexactines. The lateral rays are in the forms A and B, according to Wilson ( loc . tit.), pointed and nearly or quite smooth. In the forms C, D, E, and F they are also usually pointed, but smooth only exceptionally ; as a rule they are provided with sparse, but rather large and conspicuous spines. Sometimes I observed lateral rays with much larger and more numerous spines which, in respect to spinulation, resembled the distal ray. The lateral rays are in the forms A and B, according to Wilson (loc. tit.), 30-40 fj. long, in form C 13-44 fi, in form D 16-100 n, in form E 24-54 /*, and in form F 26-63 /x. The pinules with lateral rays more than 50 n long are mostly transitions to the microhexactines. In the ordinary pinules a sixth proximal ray is present only quite exceptionally, and here hardly ever more than 30 n long; in the pinules transitional to the microhexactines a proximal ray is gen- erally met, and in these it attains a length of 50-100 n. In regard to the spinulation, the proximal rays usually resembles the laterals. In some of the forms transitional to the microhexactines, the proximal ray is spined in a similar way to the distal. The pentactine pinules with elongated distal ray (Plate 52, fig. 15). The distal ray of these spicules is in the forms A and B examined by Wilson (loc. cit.) 300-400 fj. long, in form D 240-315 n. In forms C and F I observed only very few pinules of this kind. In these the distal ray was 350 n long. In form E I failed to find any pinules of this kind. I ascribe the absence of these spicules in this form and their scarcity in the preparations of forms C and F to the fragmentary condition of the specimen of these forms. In the forms C, D, and F the distal ray is 4. 5-6. 5 n thick at the base, conic, and generally somewhat curved. It terminates in an exceedingly long and slender, spineless terminal cone. Its middle-part bears small spines inclined towards the tip. Its maximum transverse diameter, together with the spines, is 5-14 n. In forms A and B, examined by Wilson (loc. cit.), the distal ray is similar. The lateral rays are pointed or, more rarely, rounded at the end. In the forms A and B, examined by Wilson (loc. cit.), they are 40 n long, in the forms C, D, and F, 15-38 n. The diactine pinules (Plate 52, fig. 16) appear as anisoactine, centrotyle amphioxes with numerous spines on their distal ray, and occasionally also a few HYALONEMA (PHIALONEMA) PATERIFERUM. 367 spines on their proximal ray. Wilson ( loc . cit .) gives the length of one of these spicules (of form A or B ) as 700 n, and the thickness of its tyle as 12 fi. The diactine pinules of the forms examined by me are shorter, not more than 470 n long. In form D, where I found the largest number of them, the distal ray is 140-200 /d long, 4-5 n thick at the base, conic, and attenuated distally to a very slender terminal cone. This terminal cone and a small region at the base of the ray are free from spines; the remaining parts bear small spines strongly inclined towards the tip of the ray. The proximal ray in the diactine pinules of this form (D) is 80-125 fx long. The tyle, which consists of four knob-like protuberances (the rudiments of the four reduced lateral rays), measures 9-17 /j. in transverse diameter. A diactine pinule of form C, which I measured, had a distal ray 350 n long, and 5 n thick at the base, a proximal ray 120 n long, and a central tyle 15 m in transverse diameter. The lateral rays of the ( hypodermal and hypogastral ) pentactines are, accord- ing to Wilson (loc. cit.), in the forms A and B 150-600 n long, and 12-48 n thick at the base. In form D, where alone I could measure a large number of these spicules, their lateral rays are 120-360 m long and 12-30 n thick. The proximal ray is generally longer than the lateral rays. The lateral rays are straight, smooth, and pointed; the proximal ray is similar, or, rarely, reduced in length, and thickened and rounded at the end. The hexactine megascleres. Wilson (loc. cit.) gives the measurements of one of these spicules (of form A or B) thus: — length of rays 700 n, basal thickness 48 id. In form D these hexactines have rays 25-41 n thick at the base. One of the intact ones of this form was 1.2 mm. in diameter. The choanosomal rhabds are usually centrotyle amphioxes. In the forms A and B they measure, according to Wilson (loc. cit.), 0.5-3 mm. by 8-28 n. In the forms examined by me they appear to be similar. The paratangential superficial and the radial subdermal and subgastral centrotyle amphioxes are in form D 320-520 m long and, near the middle, 3-10 n thick. The central tyle is 11-13 n in diameter. The stalk-spicules are in form A, where alone they have been observed, according to Wilson (loc. cit.), 0.13-1 mm. thick, attenuated below, and pro- vided with “the well-known annular ridges.” The acanthophores (Plate 52, figs. 17-19) are, according to Wilson (loc. cit.), in form A di- to hexactines, tetractines with unequal rays being most frequent. The measurements given by him are 900 n for the length of a diactine, and 250 n for the length of a ray of a tetractine. In form F I found di- to pentactine 368 HYALONEMA (PHIALONEMA) PATE RIFERUM. acanthophores with rays 15-30 m thick at the base. The diactines are here 550-720 n long, the tri- to pentactines 290-720 n in maximum diameter. The rays of these spicules are somewhat irregular, wavy in outline, and often slightly curved. They usually taper distally. The end itself is frequently slightly thickened and terminally rounded. The basal and middle-parts of the rays are smooth, their end-parts, for a short distance, densely spined. Among the microhexactines (Plate 50, figs. 9, 10; Plate 51, figs. 23-28; Plate 52, figs. 1, 2) forms with small spines and strongly curved rays, and forms with larger spines and only slightly curved or straight rays, can be distinguished. The former are usually much smaller than the latter. The larger forms with straight rays are connected by transitions with the pinules. The rays of the microhexactines are in the forms A and B, according to Wilson ( loc . cit.), 30-80 jj. long, and in the small ones with curved rays 2 n thick. In the forms C, D, E, and F the rays of the microhexactines are, at the base, 1-3.5 n thick, usually 1.5-2. 5 n. Those measured of form C were 55-80 n in diameter, of form D 64-128 n, of form E 55-150 n, and of form F 59-138 The small microhexactines with curved rays are regular, the six rays of the same spicule being equal in size and curvature, all straight at the base, and uniformly curved in their distal part through an angle of 45°-135°. The direction of curvature in opposite rays is usually opposite (Plate 51, figs. 23, 24, 26, 28). In the rare, large microhexactines with curved rays, the curvature is irregular, and different in the different rays of the same spicule (Plate 51, fig. 25). In the large micro- hexactines with nearly straight rays, the six rays are generally equal. Any curvature observable in them is restricted to their distal part. Of amphidiscs four forms can be distinguished: — large macramphidiscs, small macramphidiscs, large micramphidiscs, and small micramphidiscs. The large and small macramphidiscs are not clearly separated biometrically (accord- ing to their length frequency) or morphologically. Nevertheless there is, in all the four forms examined by me, a deep depression at about 100 n in the frequency-curve pertaining to these spicules, which renders it advisable to dis- tinguish them. The macra*mphidiscs shorter than 100 m I consider as small, those longer as large ones. The macramphidiscs under 100 n in length, that is the small ones, have relatively longer anchors and fewer anchor-teeth than those over 100 n in length, that is the large ones. The small macramphidiscs are clearly distinguished from the large micramphidiscs morphologically, the former having stout and smooth or nearly smooth shafts and broad terminal anchors; the latter slender and strongly spined shafts and narrow terminal HYALONEMA (PHIALONEMA) PATERIFERUM. 369 anchors. The large and small micramphidiscs are distinguished biometrically by gaps in the frequency-curves pertaining to their length. These gaps lie in the different forms in different places, between lengths of 24 and 49 p. Wilson also distinguishes four forms of amphidiscs: — macramphidiscs ( = large macram- phidiscs), amphidiscs (Wilson, loc. cit., Plate 1, figs. 10 and 11) (= small macram- phidiscs), mesamphidiscs ( = large micramphidiscs), and micramphidiscs ( = small micramphidiscs). He thinks it possible that the small macramphidiscs (with 4-6 teeth in each anchor) represent young stages of the large macramphidiscs (with 8 teeth in each anchor). I do not think this is so. The large macramphidiscs (Plate 50, fig. 15; Plate 51, figs. 2, 16-22; Plate 52, figs. 3, 4, 9, 10) have a shaft either cylindrical, and of uniform thickness throughout (Plate 52, fig. 10) or thickened towards the ends (Plate 51, fig. 18). In the smaller and medium-sized large macramphidiscs the shaft is usually nearly quite smooth (Plate 51, figs. 17, 19; Plate 52, fig. 4); in the larger ones it often bears a smaller or a larger number of very low and broad, rounded protuber- ances which are scattered irregularly over its central part. In the large macram- phidiscs (Plate 51, fig. 18) these protuberances are 6 p broad and 2 p high. The axial thread is perfectly simple, not thickened in the centre of the spicule, and there is no trace of an axial cross (Plate 50, fig. 15). The anchors are remarkably low and composed of from five to twelve teeth, most frequently eight. The individual teeth arise nearly vertically from the end of the shaft, and are curved concave towards it. The curvature is slight at the base, but increases distally, so that the axes of the end-parts of the teeth enclose angles of 30°-45° with the shaft-axis. The teeth of the same anchors are usually simi- lar (Plate 51, fig. 22); sometimes, however, particularly in the large macramphi- discs with more than eight teeth, one (Plate 51, fig. 21) or more of them are abnormally small. The teeth are T-shaped in transverse section. The upper part (of the T) is band-shaped, distally widened, at its broadest point 19-24 p in transverse diameter, and abruptly pointed; seen from above the teeth appear mitre-shaped. The lower part (of the T) is broad, low, and rounded below. It terminates some distance below the end of the teeth. The large macramphidiscs of form A and B are, according to Wilson (loc. cit.), 100-200 n long. In those of form A the shaft is 8-16 p thick. Their anchors are composed of eight teeth. In the large macramphidiscs of form A the anchors are about one fifth of the whole spicule in length. Those of form B are about one seventh. In form C the large macramphidiscs are 106-186 p long, most frequently about 137 p, and have shafts 14-22 p thick, exceptionally only 370 HYALONEMA (PHIALONEMA) PATERIFERUM. 8 /x. Their anchors are 17-30 fx long, usually one seventh to one fourth of the whole spicule, 68-101 n broad, and composed of from seven to eight teeth. The proportion of anchor-length to anchor-breadth is 100 to 273-429, on an average 100 : 339. The large macramphidiscs of form D (Plate 52, figs. 3, 4, 9, 10) are 100-318 n long, most frequently about 200 n, and have shafts 10-22 /x thick, rarely only 8 /x. Their anchors are 19-47 n long, usually one ninth to one seventh of the spicule, 55-122 n broad, and composed of from six to nine, usually eight teeth. The proportion of anchor-length to anchor-breadth is 100 to 222-420, on an average 100 : 298. The large macramphidiscs of form E are mostly regu- lar, but irregular forms also occur among them. The regular ones (Plate 50, fig. 15; Plate 51, figs. 2, 17-22) are 105-265 n long, rarely as much as 334 n, most frequently about 200 m, and have shafts 14-23 n thick. Their anchors are 17-35 n long, usually one tenth to one seventh of the whole spicule, 62-109 n broad, and composed of from eight to eleven teeth. The proportion of anchor- length to anchor-breadth is 100 to 276-500, on an average 100 : 361. The rare irregular large macramphidiscs of this form (Plate 51, fig. 16) differ from the regular by their anchors being longer and composed of less numerous and spirally twisted teeth. The irregular large macramphidisc (Plate 51, fig. 16) is 116 n long and has a shaft 20 n thick and anchors 42 fx long and 54 fx broad. The large macramphidiscs of form F are 103-188 /x long, rarely as much as 235 ix. The frequency-curve pertaining to their length has two summits, a higher one at about 136.5 ix, and a lower one at about 164 tx. The shafts of these spicules are 11-18 n thick, rarely as much as 22 /x. Their anchors are 17-30 /x long, usually one eighth of the whole spicule, 66-105 /x broad, and composed of from five to twelve teeth. The proportion of anchor-length to anchor-breadth is 100 to 320-430, on an average 100 : 363. The small macramphidiscs (Plate 51, fig. 15; Plate 52, figs. 5-8) are similar to the large ones and have, like them, a shaft which is cylindrical and of uniform thickness throughout (Plate 51, fig. 15) or thickened towards the ends (Plate 52, figs. 5, 7). The shaft is either smooth (Plate 52, fig. 6), or it bears a few low tubercles scattered irregularly over its central part (Plate 52, fig. 8). The anchors are generally one sixth to one third of the whole spicule in length, and composed of from four to seven teeth; in the smallest forms there are four or five teeth. The number of teeth in the two anchors of the same spicule is often different. The teeth are similar to those of the large macramphidiscs above described, but, particularly in the smallest form, more slender, relatively longer, and more strongly curved. HYALONEMA (PHIALONEMA) PATERIFERUM. 371 The small macramphidiscs are in the forms A and B, according to Wilson ( loc . cit.), 60-100 m long; in form C 68-100 n, most frequently about 76 m; in form D 63-96 m long, most frequently about 80 /j.; in form E 87-100 n long, most frequently about 95 m; and in form F 75-100 n long, most frequently about 93 fj . The thickness of their shafts are in form C 9-13 n, in form D 5-9 //, in form E 11-17 m, and in form F 9-13 n- The anchors of these spicules are: — in form C 18-28 n long and 40-65 n broad, the proportion of anchor-length to anchor-breadth being 100 to 143-333, on an average 100 : 258 ; in form D (Plate 52, figs. 5-8) 25-31 n long and 35-60 n broad, the proportion of anchor- length to anchor-breadth being 100 to 120-200, on an average 100 : 162; in form E (Plate 51, fig. 15) 18-25 long and 52-70 ju broad, the proportion of anchor-length to anchor-breadth being 100 to 256-340, on an average 100 : 306; and in form F 14-20 m long and 30-58 m broad, the proportion of anchor-length to anchor-breadth being 100 to 210-330, on an average 100 : 286. The large micramphidiscs (Plate 50, fig. 14; Plate 51, figs. 9-14; Plate 52, figs. 27-29) have a shaft 1-3 n thick and cylindrical throughout or slightly and gradually thickened in or near the middle. The shaft is beset with irregular obtuse spines 0.5-2 /j. long. These are generally very numerous, and usually occupy all parts of the shaft with the exception of its ends. The terminal anchors are long, rather narrow, and very obtuse. Sometimes their length is sufficient to bring the teeth of the two opposite anchors of the same spicule nearly into contact with each other (Plate 50, fig. 14; Plate 51, fig. 9). The individual teeth arise steeply from the shaft. They are curved only slightly in their basal part, but strongly and more or less abruptly bent down a short distance from their origin. Their distal and middle-parts, beyond this bend, are only slightly curved or straight and enclose a small angle, 20° or less, with the shaft-axis. Sometimes this angle is 0 (Plate 52, fig. 8); then they are parallel to the shaft. The large micramphidiscs of forms A and B are generally simple. Excep- tionally, however, they have more than two anchor-crowned rays. The ordinary simple ones are, according to Wilson (loc. cit.), 50-80 /x long, and have anchors which are slightly more than a third of the whole spicule in length and com- posed of eight teeth. One of the large micramphidiscs with more than two anchor-crowned rays, measured by Wilson (loc. cit.), was 72 /x in maximum diam- eter, and had five rays, three of which bore terminal anchors. The large micramphidiscs of form C are 49-66 m long, most frequently about 57 n, and have anchors 15-28 ^ long, less than a third to nearly half of the whole spicule, 372 HYALONEMA (PHIALONEMA) PATERIFERUM. and 15.5-28 n broad. The proportion of anchor-length to anchor-breadth is 100 to 76-100, on an average 100 : 92. Those of form D (Plate 52, figs. 27-29) are 35-77 ju long, most frequently about 52 n, and have anchors 1 1-27 n long, one third to nearly a half of the whole spicule, and 9.5-22 n broad. The proportion of anchor-length to anchor-breadth is 100 to 62-91, on an average 100 : 76. Those of form E (Plate 50, fig. 14; Plate 51, figs. 7-14) are 47-86, most frequently about 73 n long, and have anchors 18-33 n, two fifths to nearly half of the whole spicule, and 14-29 n broad. The proportion of anchor-length to anchor-breadth is 100 to 57-87, on an average 100 : 72. Those of form F are 35-68 n long, most frequently about 53 n, and have anchors 10-25 n long, a quarter to nearly half of the whole spicule, and 7-19 /x broad. The propor- tion of anchor-length to anchor-breadth is 100 to 63-88, on an average 100 : 73. The small micramphidiscs (Plate 50, figs. 11-13; Plate 51, figs. 3-6; Plate 52, figs. 24-26) have a straight shaft, 0.7-1. 5 n thick, which is either cylindrical and of uniform thickness throughout, or slightly and gradually thickened in or near the middle. It usually bears a few scattered spines up to 1 m in length in its middle-part. The terminal anchors are from under a third to two fifths of the whole spicule in length. They are obtuse in shape and composed of about eighteen teeth. The individual teeth arise vertically from the shaft, are nearly straight in their basal part, and then curve downwards. This curvature decreases distally. The ends of the teeth are nearly straight and enclose only small angles with the shaft-axis, or are parallel to it. The small micramphidiscs are in forms A and B, according to Wilson ( loc . cit.), 20-25 m long. In form C they are 22-31 n long, most frequently about 26 n; in form D 18-31 yu, most frequently about 24 /q in form E, 15-30 /z, most frequently about 21 /q and in form F 14-24 n, most frequently about 20 n long. Their anchors are in form C 4-1 n long and 5.5-12.5 n broad, the proportion of anchor-length to anchor-breadth being 100 to 95-178, on an average 100 : 140; in form D (Plate 52, figs. 24-26) 4-9 n long and 7-9.5 m broad, the proportion of anchor-length to anchor-breadth being 100 to 100-200, on an average 100 : 153; in form E (Plate 50, figs. 11-13; Plate 51, figs. 3-6) 4. 5-9. 5 n long and 5-10 n broad, the proportion of anchor-length to anchor-breadth being 100 to 87-150, on an average 100 : 114; and in form F 3-6 n long and 4-8 m broad, the proportion of anchor-length to anchor-breadth being 100 to 100-175, on an average 100 : 140. Eight specimens and three fragments of this species were collected in the central and eastern part of the Tropical Pacific. One specimen and three fragments of form A were trawled off Panama at Station 3363, on 26 February, HYALONEMA (PHIALONEMA) PATERIFERUM. 373 1891; 5° 43' N., 85° 50' W. ; depth 1788 m. (978 f.); they grew on white Globi- gerina ooze; the bottom-temperature was 37.5°. One specimen of form A was trawled off Panama, at Station 3376, on 4 March, 1891; 3° 9' N., 82° 8' W. ; depth 2070 in. (1132 f.) ; it grew on gray Globigerina ooze; the bottom-tempera- ture was 36.3°. The two specimens of form B were trawled in the Central Tropi- cal Pacific at Station 3684 (A. A. 17) on 10 September, 1899; 0° 50' N., 137° 54' W. ; depth 4504 m. (2463 f.); they grew on light yellow-gray Globigerina ooze. The single specimen of form C was trawled off northern Peru at Station 4651, on 11 November, 1904; 5° 41.7' S., 82° 59.7' W., Aguja Point S. 83° E., 206 km. (Ill miles) ; depth 4063 m. (2222 f.) ; it grew on sticky, fine, gray sand; the bot- tom-temperature was 35.4°. The single specimen of form D was trawled off north- ern Peru W. S. W. of Aguja Point, at Station 4656 on 13 November, 1904; 6° 54.6' S., 83° 34.3' W. ; depth 4063 m. (2222 f.); it grew on fine, green mud mixed with gray ooze; the bottom-temperature was 35.2°. The specimen of form E was trawled in the Eastern Tropical Pacific, at Station 4721, on 15 Janu- ary, 1905; 8° 7.5' S., 104° 10.5' W.; depth 3811 m. (2084 f.); it grew on light brown Globigerina ooze. The single specimen of form F was trawled in the Eastern Tropical Pacific at Station 4742, on 15 February, 1905; 0° 3.4' N., 117° 15.8' W. ; depth 4243 m. (2320 f.); it grew on very light, fine Globigerina ooze; the bottom-temperature was 34.3°. There can, I think, be no doubt that the four sponges described above all belong to Wilson’s Hyalonema pateriferum. The specimens of this species studied by Wilson from the Stations 3363 and 3376 appear to be fairly identical with each other, but differ from all the rest. The specimens described by him from Station 3684 (A. A. 17) are likewise identical with each other arid different from all the rest. The four specimens examined by me, which all come from different stations, differ from each other and from the specimens described by Wilson. The following are the fourteen more important spicule-dimensions, of which the averages and the nature of the variation have been ascertained: — a, the length of the distal ray of the ordinary pinules; b, the basal thickness of this ray; c, the length of the lateral rays of the ordinary pinules; d, the diameter of the microhexactines ; e, the length of the large macramphidiscs ; /, the thickness of the shafts of these spicules; g, the average proportion of the length to the breadth of the anchors of these spicules; h, the length of the small macramphi- discs; i, the thickness of the shafts of these spicules; k, the average proportion of the length to the breadth of the anchors of these spicules; l, the length of the large micramphidiscs ; m, the average proportion of the length to the breadth 374 HYALONEMA (PHIALONEMA) PATERIFERUM. of the anchors of these spicules; n, the length of the small micramphidiscs; and o, the average proportion of the length to the breadth of the anchors of these spicules. a, The length of the distal ray of the ordinary pinules varies in the forms A, B, and F between about the same limits. The other forms differ, in respect to this dimension, from these and from each other, b, The distal rays of the ordinary pinules are, in the forms A, B, E, and F, usually about 5 n thick at the base, in forms C and D considerably thinner, c, The shortest lateral rays of the ordinary pinules are in the forms A and B 30 n long, in the forms E and F 24- 26 in form D 16 and in form C only 13 m- d, The diameter 1 of the micro- hexactines varies in the forms A, B, and E between fairly equal limits (55-160 m)- In the forms D and F the largest microhexactines are smaller, only 128 /x in diameter in the former and 138 n in diameter in the latter. In form C these spicules are much smaller still, e, The length of the large macramphidiscs varies between similar limits (100-235 m) in the forms A, B, C, and F. In the forms D and E the largest large macramphidiscs are 300 n or more long, and also have a much greater average size. /, The shafts of the large macramphi- discs are thickest in forms C and E, thinner in form D and F, and still thinner in form A. In form B this dimension is not known, g, The average proportion of anchor-length to anchor-breadth is in the forms E and F 100 : 361 and 100 : 363 respectively; in form C 100 : 339, and in form D only 100 : 298. In the forms A and B studied by Wilson it is not known. Since, however, Wilson ( loc . cit.) states that in the former the anchor-length is one seventh and in the latter one fifth of the length of the whole spicule, which is said to be the same in both, it may be assumed that these two forms differ in respect to this anchor- proportion from each other, h, The small macramphidiscs are in the forms A , B, C, and D fairly equally long, in the forms E and F they are longer, i, The thick- ness of the shafts of the small macramphidiscs is greatest in form E, equal and smaller in form C and F, and still smaller in form D. In forms A and B this dimension is not known, k, The average proportion of anchor-length to anchor- breadth of the small macramphidiscs is in the forms C, E, and F 100 to over 250, in form D only 100 to 162. In the forms A and B this anchor-proportion is not known. I, The length of the large micramphidiscs varies in the forms A, B, and E between nearly equal limits (47-80 n), and is in form E most frequently about 73 /x. In form C these spicules are not so large, most frequently 57 m long, and in forms D and F nearly equal and still shorter, most frequently 52 and 53 n 1 In the forms A and B, where only the ray-length is given, the double ray-length is taken as the diameter. HYALONEMA (PHIALONEMA) PATERIFERUM. 375 respectively, m, The average proportion of the anchor-length to the anchor- breadth of the large micramphidiscs is in form C 100 to 92, in the forms D, E, and F 100 to 72-76. According to Wilson ( loc . cit.), the length of the anchors of these spicules is, both in forms A and B, a third of the length of the whole amphidisc; the anchors of these spicules are in these two forms therefore probably also about equal in respect to the proportion between length and breadth, n, In forms A and B the length (20-25 /j.) of the small micramphidiscs is equal. In forms C and I) these spicules are larger, most frequently about 26 and 24 n long respectively. In forms E and F they are smaller, most frequently about 20 and 21 fi long respectively, o, The average proportion of anchor- length to anchor-breadth of the small micramphidiscs is in form D 100 to 153, in form C and F 100 to 140, and in form E 100 to 1 14. In the forms A and B this proportion is not known. The affinities of the six different forms in respect to these further qualities are tabulated below: — According to this table the units of all the fifteen possible pairs of forms, with the exception of those of two, coincide with respect to only 1-4 of the 376 SKIANEMA. fourteen qualities here discussed, and must therefore, I think, be kept distinct. The two pairs A—B and E-F are more similar. The units of the first coincide in respect to nine, the units of the second in respect to seven of these fourteen qualities. The pair A-B consists of the two forms described by Wilson, and it must, in comparing these, be kept in mind that this author does not give the measurements of all the dimensions and proportions (a-o) here discussed, and of the dimensions he does give mentions only to limits, but states neither the biometric character of the variation nor the averages of the individual measure- ments. As his measurements are insufficient for this comparison it is probable that these two forms do not coincide in the manner indicated by the figures given in the above table. However this may be, there doubtlessly exists a con- siderable difference between the large macrampliidiscs of these forms, the length of the anchors being one seventh of the length of the whole spicule in the one, and one fifth in the other. I think this difference by itself sufficient to keep the forms A and B distinct. The forms E and F are certainly very similar. The chief differences between them are that the large macramphidiscs and large micramphidiscs are larger, and that the breadth of the anchors of the small micramphidiscs is relatively smaller in the former than in the latter. The specimens of both these forms are very fragmentary, which renders it doubly difficult to decide whether the observed differences between them should be considered sufficient to keep them distinct or not. In doubtful cases like this; it is, I think, better to keep similar specimens distinct rather than to unite them. The differences between these six lots of sponges are slight, not correlated to the distance between the stations where they were obtained, and in my opinion insufficient, for varietal distinction. They render it however advisable to describe them as different forms of Hyalonema pateriferum. These forms are not equivalent, E and F being much more similar than any other pair, with the exception possibly of A and B, SKIANEMA, subgen. nov. Species of Hyalonema of which the amphidiscs of one kind have relatively rather large, broad and low, umbrella-shaped terminal anchors. The collection contains three specimens of this subgenus, which belong to two species, both of which are new. HYALONEMA (SKIANEMA) AEQUATORIALE. 377 Hyalonema (Skianema) aequatoriale, sp. nov. Plate 99, figs. 1-37; Plate 100, figs. 1-12; Plate 101, figs. 1-3. A single specimen of this species was trawled in the Eastern Tropical Pacific at Station 4742 on 15 February, 1905; 0° 3.4' N., 117° 15.8' W. ; depth 4243 m. (2320 f.); it grew on a bottom of very light, fine Globigerina ooze; the bottom- temperature was 34.3°. The locality where it was found lies nearly under the equator and to this the name refers. Shape and size. The single specimen is somewhat lacerated and fragmentary. It now appears (Plate 99, fig. 17) flattened and elongate. One end is rounded. At the other it terminates with a nearly straight margin vertical to the two longer sides. It is 71 mm. long, 45 mm. broad, and has a maximum thickness of 15 mm. In life it was probably not much thinner than broad. The straight terminus is the upper gastral face. It is slightly depressed in its middle-part, from which a gastral cone arises. This cone is surrounded by thin, more or less vertical, radiating lamellae, between which extend extensive cavities, now much com- pressed. The rounded end is the lower, and from it doubtlessly arose in life a stalk, which has, however, been completely lost. The colour in spirit is whitish brown. Traces of elongate flagellate chambers about 75 m broad can be made out here and there in the sections. The skeleton. A dense spicule-fur covers all intact parts of the surface (Plate 101, figs. 1, 2a, 3). Between the basal parts of the distal rays of the superficial pinules forming this fur are met small macramphidiscs, generally with the shaft vertical to the surface of the sponge (Plate 101, fig. 2c). The superficial membranes are supported by the lateral rays of the (dermal and gastral) pinules, and the (hypodermal and hypogastral) pentactines; paratan- gential rhabds also occur in it in considerable numbers (Plate 101, fig. 3). Just below the surface numerous large macramphidiscs are found (Plate 101, fig. 2d). A loose bundle of large amphioxes occupies the axial part of the sponge. This bundle extends completely into the gastral cone. More or less radially extending rhabds occur in the choanosome. Most of the rhabds in the superficial mem- branes and in these bundles are amphioxes; some diactine styles or tylostyles, however, also occur. Microhexactines are scattered throughout the choano- some in large numbers. Large and small micramphidiscs are also found in it. These spicules are, however, rather rare. In the interior of the gastral cone a good many spheres have been observed. 378 HYALONEMA (SKIANEMA) AEQUATORIALE. Foreign skeletal elements are always met in the deep-sea hexactinellids which have, like the specimen here described, been somewhat injured in capture. 1 do not remember, however, ever having seen a sponge so rich in foreign spicules as this one. The spicules in question could be determined as foreign because they are identical with the pentac tines, pinules, hexasters, amphidiscs, etc., of Holascella euonyx, Hyalonema ( Hyalonema ) agassizi, Hyalonema ( Prionema ) fimbriatum, Hyalonema ( Phialonema ) pateriferum, and Hyalonema ( Prionema ) spinosum brought up in the same haul together with the sponge here under discussion. The dermal pinules (Plate 99, figs. 29-31) are generally pentactine, rarely hexactine. The distal ray is straight, 200-260 /x long, and 5-8 /x thick at the base. It ends in a rather slender sharp-pointed terminal cone, and bears every- where, except at the base and at the tip, rather slender straight or slightly curved spines, which are all strongly inclined towards its tip. The maximum thickness of the distal ray, together with the spines, is 25-42 n . The lateral rays are cylindroconical, pointed, spiny, and 30-45 m long. The proximal ray of the rare hexactine forms (Plate 99, fig. 29) is 9-42 n long. The gaslral pinules (Plate 99, figs. 25-28, 36) are a little larger than the dermals and appear always to be pentactine. Their straight distal ray is 212- 275 /x long, and 6-9 /x thick at the base. It ends with a long and slender sharp- pointed terminal cone and bears everywhere, except at the tip and at the base, remarkably sparse spines. These spines are long, slender, straight or slightly curved, and strongly inclined towards the tip of the ray. The maximum thick- ness of the distal ray, together with the spines, is 23-39 m- The lateral rays are 35-48 m long and, like those of the dermal pinules, cylindroconical and spined. The hypodermal and hypogastral pentactines seem to be quite similar. Their rays are conical, straight, and blunt. The proximal ray is generally 0.4-1 mm. long, and 16-50 m thick at the base. The lateral rays are 140-800 /x. The hexactine megascleres are mostly 360-850 /x in diameter, and have coni- cal, blunt, and straight rays 9-31 m thick at the base. A few fragments observed in the preparations indicate that some of these spicules attain a larger size. The ordinary superficial and choanosomal amphioxes are straight or slightly curved and usually more or less centrotyle. In some no trace of a central thickening could be made out. These spicules are 0.25 /x— 1-9 mm. long, and 7-26 m thick near the middle. The central tyle is sometimes 6 m in transverse diameter, usually about 0.3 m more than the adjacent parts of the spicule. The HYALONEMA (SKIANEMA) AEQUATORIALE. 379 “central” tyle is often situated a considerable distance away from the middle of the length of the spicule, many of these centrotyle amphioxes being markedly anisoactine. The styles and tylostyles are, like the amphioxes above described, centrotyle diactine rliabds. One of their rays is similar to an amphiox-ray, the other is reduced in length and rounded, and generally also thickened at the end. These spicules are 0.5-2 mm. long. They are slightly thickened at the morphological centre, in which the axial cross can always be made out, and are here 8-25 y thick. The rounded end (terminal tyle) is 8-40 y in diameter and usually separated from the remaining part of the spicule by an attenuation. In this attenuation, or neck, the spicule is 1-11 y thinner, usually 3-6 y, than the rounded end (terminal tyle). The large amphioxes of the rhabd-bundle which forms the skeletal axis of the sponge-body and terminates in the gastral cone are 2 mm. and more (the long ones are broken) long and 30-60 y thick. The spheres are regularly spherical, oval, or irregular, potato-shaped. They measure 17-170 y in maximum diameter, most frequently about 30 y. All contain a granular centrum round which silica-layers of somewhat varying refractory index have been deposited. The surface is in the smaller spheres regular, smooth, and continuous, in the larger it is usually irregular. As an example I shall describe a typical large sphere. This spicule is 168 y long and 157 y broad. It has an oval granular centrum 12 y long and 7 y broad. The granules in it are numerous, and about 1 y in diameter. In the silica, which is perfectly hyaline, a concentric stratification around the centrum can be made out very clearly. In one place a watchglass-shaped granular body, which appears sickle-shaped in profile (optical section), is interpolated between two successive layers of ordinary hyaline silica. A number of groove-like inden- tures, sometimes 2 y deep, are visible on the surface of the sphere. Several of these radiate from one point. * The microhexactines (Plate 99, figs. 3-10, 32-35) are 60-96 y in maximum diameter. In some all the rays are fairly equal; in others two opposite rays are considerably longer than the other four. The latter are sometimes nearly twice as long as broad. The rays are 1.8-2. 4 y thick at the base. They are conical, finely pointed, and covered with very minute spines. The basal part, usually about half of the total length of the whole ray, -is nearly straight, the distal part curved. This curvature is usually greater at the point where the basal straight part passes into the distal curved part than farther on. The whole curvature is 380 HYALONEMA (SKIANEMA) AEQUATORIALE. such that the directions (tangents) of the proximal and distal end-parts of the ray generally enclose an angle of 105°-130°. The tips of opposite rays point in opposite directions. From a morphological point of view four kinds of amphidiscs are to be dis- tinguished: — A, larger forms with low (short) and very broad anchors, about a third of the length of the whole spicule; B, forms intermediate in size with rela- tively large anchors, about half as long as the whole spicule; C, forms inter- mediate in size with small, relatively broad anchors, a fourth to a fifth of the whole spicule in length ; and D, small forms with more slender anchors. As the length frequency-curves in Figure 24 show, these four morpho- logically different kinds of amphidiscs are by no means all clearly separated also biometrically. In fact the curve pertaining to the amphidiscs of the groups B and C overlap to a large extent, and only the curve pertaining to group D is clearly distinct from the others. In view of the great morphological difference between the groups B and C and the total absence of intermediate forms connecting these two groups, I do not hesitate to consider them as different kinds of amphidiscs. I distinguish altogether four different kinds of amphidiscs in this sponge: — large (group A) and small (group B) macramphidiscs, and large (group C ) and small (group D) micramphidiscs. The length frequency-curves pertaining to the first three forms are quite simple and without deep depressions; these groups are biometrically homogeneous. The curve pertaining to the small micramphidiscs (group D) is complicated, however, by two deep depressions descending to the 0-line, which divide it into three parts. Since, however, the larger, the medium, and the smaller small micramphidiscs pertaining to the three distinct elevations of this curve are quite similar in shape, I do not think it advisable to distinguish sub- groups within this amphidisc-group. The regular large viacr amphidiscs (Plate 99, figs. 1, 2, 37; Plate 100, figs. 5-11; Plate 101, fig. 2d) are 105-298 m long, usually 122-257 ^, most fre- quently about 180 /x. The shaft is straight, cylindrical, perfectly smooth, and 14-27 m thick, generally 19-27 The terminal anchors are 42-87 /x long, about a third of the whole spicule, and 90-195 /j. broad. The proportion of the length to the breadth of the anchors is 100 to 191-288, on an average 100 : 236.8. Each anchor consists of from eight to eleven teeth. The teeth of the two anchors of the same spicule are generally situated alternately. The teeth arise nearly vertically from the ends of the shaft, are curved very slightly in their proximal part, but very strongly in their distal part, and their tips converge Length of Amphidiscs (/a). Length O 11.92 13.11 14.42 15.86 17.45 19.19 21.11 23.23 25.55 28.10 30.91 34.00 37.40 41.14 45.26 49.78 54.76 60.24 66.26 72.89 80.18 88.20 97.02 106.72 117.39 129.13 142.04 156.25 171.87 189.06 207.97 228.76 251.64 304.49 - 13.11- 14.42- - 15.86 - 17.45 - 19.19 - 21.11 - 23.23 - 25.55 -j - 28.10 - 30.91- - 34.00- - 37.40- - 41.14- - 45.26- - 49.78- - 54.76- - 60.24- - 66.26- - 72.89 80.18- 88.20- - 97.02- - 106.72 117.39- 129.13- - 142.04- 156.25- 171.87 - 189.06 -207.97 -228.76-1 -251.64 .304.49 334.93- co Number I in t-1 in r 3 Si 3 £ crq crq rt — o> -a 3* m 3 •o ■g* to n co CD o 5 3 s: D. CO* o CO Fig. 24. — Amphidiscs. Macramphidiscs in general 382 HYALONEMA (SKIANEMA) "AEQUATORIALE. very markedly. The distances between the ends of opposite teeth are therefore smaller than the breadth of the anchor. While the latter is, as above stated, 90-195 is, the former is only 83-164 n, that is 7-20 n less. The outer band- shaped part of the tooth attains its maximum width of 17-29 n about two thirds of its length from its base. Distally it is simply rounded off. The keel in the larger forms is, at the base of the tooth, about 30 n high, decreases in height distally, and terminates some distance within the tip of the tooth. Besides the regular large macramphidiscs above described, a good many irregular large macramphidiscs (Plate 99, figs. 18-20) have been observed. The irregularity most frequently observed is an inequality of the two anchors of the same spicule. These may differ in size, in the proportion of their length to their breadth, and in the number of teeth composing them. The irregular large macramphidiscs of this kind are about as large as the regular ones. Much more rarely smaller forms are met, in which either a large conic protuberance arises from the apex of one of the anchors (Plate 99, fig. 18) or the anchors are quite irregular. The teeth composing such anchors are exceedingly unequal, some being hypertrophied, twisted, or otherwise deformed, others rudimentary (Plate 99, figs. 19, 20). The small macramphidiscs (Plate 100, figs. 1-4, 12; Plate 101, fig. 2c) are 70-120 /d long, most frequently about 84.2 /d. The shaft is straight, cylindrical, perfectly smooth, and 6.5-13 /i thick. The terminal anchors are 38-50 m long, about half the whole spicule, and 37-84 n broad. The proportion of the length to the breadth of the anchors is 100 to 120-175, on an average 100 : 146.6. Each anchor is composed of from ten to twelve teeth. The teeth of the two anchors of the same spicule are generally situated alternately, but this alternation is only exceptionally regular, usually it is more or less irregular. The individual teeth are curved quite uniformly for the greater part of their length through about a quarter of a circle, so that the whole anchor is more or less hemispherical in shape. Their extreme tips are strongly bent inward and converge, so that the distance between the ends of opposite teeth is usually about 6 ^ less than the breadth of the anchor. The outer band-shaped part of the tooth attains its maximum breadth of 10-14 ix in its distal half, and is rounded or, more rarely, blunt-pointed at the end. Differences in the number of teeth of the two anchors of the same spicule, differences in the size of the teeth of the same anchor (Plate 100, fig. 3), and other irregularities often occur. The large micramphidiscs (Plate 99, figs. 11-16) are 54-84 m long, most HYALONEMA (SKIANEMA) UMBRACULUM. 383 frequently about 69.5 n. The shaft is straight or slightly curved, and of a uniform thickness of 2.5-5 n throughout or slightly centrotyle. It bears very low and broad, tubercle-like, scattered protuberances (spines). The terminal anchors are 12-18 n long, a fifth to a fourth of the whole spicule, and 19-25 p broad. The proportion of the length to the breadth of the anchors is 100 to 134-167, on an average 100 : 148.1. Each terminal anchor consists of from twelve to sixteen teeth. The individual teeth are curved only slightly in their proximal and distal parts, but rather strongly in their middle-part. Their total curvature is such that their nearly straight ends diverge. The anchor-teeth are rather slender and pointed at the end. The small micramphidiscs (Plate 99, figs. 21-24) are 14-25.5 n long, most frequently about 18.3 p. The shaft is straight or slightly curved, generally of a fairly uniform thickness of 0.7-1. 2 p throughout, and covered with minute scattered spines. The terminal anchors are 3.5-8 m long, a quarter to a third of the whole spicule, and 4.5-8 n broad. The proportion of the length to the breadth of the anchors is 100 to 81-143, on an average 100 : 98. The individual teeth are rather strongly and uniformly curved in their proximal part, and nearly straight in their distal part. The straight distal parts of the teeth of the same anchor are more or less parallel. The nearest allies of the above sponge are Hyalonema' {Skianema) umbra- culum and H. ( Thallonema ) geminatum. From H. (S) . umbraculum it differs by having smaller large micramphidiscs, from H. ( T .) geminatum by being desti- tute of the geminate amphidiscs and the different shape of the pinules, and from both by the possession of spheres. Hyalonema (Skianema) umbraculum, sp. nov. Plate 101, figs. 4-17; Plate 102, figs. 1-8; Plate 103, figs. 1-36. Two fragmentary specimens of this species were trawled in the Central Tropical Pacific at Station 4740 on 11 February, 1905; 9° 2.P S., 123° 20.1' W. ; depth 4429 m. (2422 f.); they grew on a bottom of dark gray Globigerina ooze; the bottom-temperature was 34.2°. The terminal anchors of the large macramphidiscs are very broad and low, umbrella-shaped. To this the name refers. Shape and size. The larger specimen is an irregular oval lamella with lacerated margin, from one of the narrow ends of which a couple of stout stalk- spicules protrude. The lamella is 62 mm. long, 39 mm. broad, and about 384 HYALONEMA (SKIANEMA) UMBRACULUM. 2 mm. thick. It has obviously been strongly compressed during or after capture, and I do not think that the living sponge, of which it once formed a part, was at all lamellar. The other specimen (fragment) is similar but much smaller. The colour in spirit is light brown. The skeleton is composed of superficial pinnies, hypodermal arid hypogastral pentactines, hexactine megascleres, choanosomal and superficial rhabds, acan- thophores, axial amphioxes forming an upper continuation of the stalk in the sponge-body, stalk-spicules proper, microhexactines, diactine microhexactine- derivates, and amphidiscs. The hexactine megascleres are exceedingly scarce. The superficial and choanosomal rhabds are for the most part centrotyle am- phioxes, but diactine tylostyles also occur among them. The microhexactines are abundant, their diactine-derivates very rare. The amphidiscs are of four kinds: — large and small macramphidiscs, and large and small micramphidiscs. The small micramphidiscs are remarkably scarce. The dermal and gastral superficial pinules (Plate 103, figs. 9-13) appear to be quite similar. All the pinules observed were pentactine. The distal ray is straight, 178-290 n long, most frequently about 240 and 4-11 thick at the base. It ends with a rather long and slender spineless terminal cone, and its basal part is also free from spines. The middle-part of the distal ray is, for about two thirds of its length, covered with straight or slightly curved spines, which are strongly inclined towards its tip. The spines situated half way up the ray are the largest. The maximum thickness of the distal ray, together with the spines, is 27-40 The lateral rays are cylindroconical, blunt, spiny, and 28-48 m long. The rays of the hypodermal and hypogastral pentaclines are cylindroconical and very blunt. In the intact pentactines observed the proximal ray is 370- 480 n long, and 14-18 n thick at the base, while the lateral rays attain a length of 120-240 ij.; however, judging from the fragments of larger ones found in the preparations, the rays of these pentactines must frequently attain a much larger size. The largest lateral rays of fragmentary pentactines observed attain 1 mm. in length and 70 m in thickness at the base. These very large fragments may, however, be parts of foreign spicules. One of the very rare hexactine megascleres measured is 480 n in maximum diameter, and has terminally rounded, cylindroconical rays 12 /i thick at the base. One of the rays of this spicule is considerably longer than the other four. The choanosomal and superficial amphioxes are centrotyle, 0.5-2. 5 mm. long, usually 1-1.5 mm., and 11-26 ^ thick near the centre. The central tyle is 14- HYALONEMA (SKIANEMA) UMBRACULUM. 385 28 n in transverse diameter, that is 1-3 ix more than the adjacent parts of the spicule. The diactine tylostyles are much more frequent in the smaller specimen than in the larger. They are about 1 mm. long, and at the morphological cen- trum, where a slight thickening is to be noticed, are 9-16 n in transverse diameter. The rounded end is 20-28 n, and the attenuated “neck,” separating it from the rest of the spicule, is 11-15 n thick. The rhabds of the axial skeleton, which form the upper continuation of the stalk within the body of the sponge, are 50-100 n thick. As nearly all these spicules found in the preparations are broken, I could not determine their length. The few large spicules of the stalk proper are 540-630 n thick. The acanthophores of the basal part of the sponge (Plate 101, figs. 15-17) have from two to four rays. The tri- and tetractines are 340-580 n in maximum diameter, their rays being 14-40 n thick at the base. The extreme tips of the rays are generally spineless, smooth, simply rounded, and dome-shaped. On this smooth end-part follows a spiny belt, usually occupying from a quarter to a half of the whole ray. Proximally the spines in these belts become smaller and smaller until they disappear altogether, leaving from half to three quarters of the ray entirely smooth. The microhexactines (Plate 101, figs. 4-7, 11-14) are 40-100 n in diameter, on an average 64.3 n. The rays are either equal, or two opposite ones exceed the other four in length. The basal part of the rays is quite straight, the distal part, usually a little less than half of the ray, uniformly curved and so strongly that the directions (tangents) of the basal half and the tip of the ray enclose an angle often as small as 90° or even smaller. The rays are conical, 1.1-1. 8 n thick at the base, and end in fine points. They are fairly smooth or only slightly roughened by barely visible spines. Besides these regular microhexactines a few diactine microhexactine-derivates (Plate 101, fig. 14) have been observed. These spicules appear as centrotyle amphioxes with fine, curved end-parts. Their surface is more rough (spiny) than that of the regular microhexactines. The measurements of a typical spicule of this kind are: — length 91 n, diameter of central tyle 3 n, basal thickness of rays 1.5 n. Morphologically two main kinds of amphidiscs can be distinguished: — those with relatively large and broad terminal anchors and those with inter- mediate or relatively small, not particularly broad anchors. The former, which are 78-280 /* long, I consider as macramphidiscs ; the latter, which are 16-99/x long, as micramphi discs. 386 HYALONEMA (SKIANEMA) UMBRACULUM. The larger macramphidiscs have very broad and rather short anchors, usually about a third of the whole spicule in length. The smaller have rela- tively much longer anchors, usually about half the whole spicule in length. Forms intermediate in respect to the proportion of the length to the breadth of the anchors connect the larger, shorter- and the smaller, longer-anchored kinds of these spicules. These intermediate forms are, however, far from numerous. The length frequency-curve in Figure 25 shows that the larger (short- anchored) and the smaller (long-anchored) macramphidiscs are very clearly distinguished biometrically. This biometrical distinction, together with the rarity of the forms transitional between the two morphologically, makes a sub- division of the macramphidiscs into two subgroups necessary; namely: — large macramphidiscs, larger forms with anchors usually about a third of the length of the whole spicule; and small macramphidiscs, smaller forms with anchors usually about half of the whole spicule in length. The part of the length frequency-curve pertaining to the micramphidiscs is divided, by a deep depression extending quite down to the 0-line, into two parts, one comprising the larger forms, 54-99 n in length, the other comprising the smaller forms, 16-38.7 n in length. Although the larger and the smaller of these spicules differ morphologically only in so far as the anchors are on the whole relatively broader in the former than in the latter; nevertheless I think it advisable to distinguish also in this main amphidisc-group two subgroups, namely, large micramphidiscs, comprising the larger forms with broader anchors, and small micramphidiscs, comprising the smaller forms with narrower anchors. The length frequency-curves pertaining to the large and small macramphi- discs are quite simple and have, each, only one summit; these two amphidisc- groups are obviously homogeneous. The curves pertaining to the micramphi- discs on the other hand have, each, two depressions, dividing each into three parts. Although this division is very well-marked, particularly in the small micramphidiscs, I do not propose further to subdivide these subgroups of amphi- discs because I was unable to detect any morphological differences between the respective amphidiscs to which the different elevations of the curves pertain. Thus I distinguish four kinds of amphidiscs in this sponge : — large and small macramphidiscs, and large and small micramphidiscs. The regular large macramphidiscs (Plate 102, figs. 1, 2, 7, 8; Plate 103, figs. 1-8, 14-23) are 110-280 n long, most frequently about 268.4 n long. The shaft is straight, cylindrical, smooth, and 17-26.5 m thick. The terminal anchors Length of Amphidiscs (/A. Fig. 25. — Amphidiscs. 388 HYALONEMA (SKIANEMA) UMBRACULUM. are 51-93 n long, usually about a third of the whole spicule, and 105-190 n broad. The proportion of the length to the breadth of the anchors is 100 to 141-316, on an average 100 : 225.3. The number of teeth in the anchor is from eight to ten. The two anchors of the same spicule are usually composed of the same number of teeth, and in this case the teeth of two anchors are generally regularly alternate. Sometimes the number of teeth is not the same in the two anchors of the same amphidisc, and in that case they of course do not alternate regularly. The individual teeth arise nearly vertically from the ends of the shaft, and are curved only slightly in their proximal half, but strongly in their distal half. This curvature is so great, that the tips of the teeth become strongly convergent, and the distance between the ends of opposite teeth is 12-32 n less than the (maxi- mum) breadth of the anchor. The outer band-shaped part of the tooth attains its maximum breadth a little distance distally from the middle of its length, and is here sometimes 32 n broad. At its distal end the tooth is simply rounded off. Besides these regular forms several irregular large macramphidiscs (Plate 101, figs. 8-10) have been observed. In these spicules one or both of the terminal anchors are irregular, and the shaft bears, besides the terminal anchor-teeth, other protuberances which arise — usually in a verticil - from its middle-part. All these supernumerary protuberances terminate at the (hypothetical) oval wall of the amphidisc-cell, and are here abruptly bent or slightly extended to terminal discs. The small macramphidiscs (Plate 102, figs. 3-6; Plate 103, figs. 24-26) are 78-128 m long, most frequently about 112 tx. The shaft is straight, cylindrical, smooth, and 6-11.5 n thick. The terminal anchors are 37-67 ^ long, about half the whole spicule, and 53-104 ^ broad. The proportion of the length to the breadth of the anchors is 100 to 138-176, on an average 100 : 150.6. The termi- nal anchors consist of ten to thirteen teeth. The number of teeth is, as in the large macramphidiscs, not always the same in the two anchors of the same spicule. When it is the same the teeth of opposite anchors are usually situated alternately; when it is not the same, there is no regular alternation of teeth. The teeth arise nearly vertically from the ends of the shaft and are curved quite uniformly, approximately through a quarter of a circle, to within a short distance of the tip. The anchors are therefore nearly hemispherical in shape. The outer band-shaped part of the tooth attains its maximum width of 15-20 m some distance distally from the middle of its length. Sometimes its broadest part lies quite close to the distal end, and in this case this end is broad and rounded (Plate 102, fig. 3); sometimes it lies some distance from the end, and HYALONEMA (SKIANEMA) UMBRACULUM. 389 then the end is attenuated and bluntly pointed (Plate 102, fig. 5). The distal end-parts of the outer band-shaped portions of the teeth are abruptly bent inward and strongly convergent, so that the distances between the ends of opposite teeth are 5-15 n less than the (maximum) breadth of the anchor. The keel retains a considerable height to within a short distance of the end of the tooth, and then terminates more or less abruptly. Seen in profile the tip of the tooth therefore resembles an eagle’s beak. The large micramphidiscs (Plate 103, figs. 31-36) are 54-99 n long, most frequently about 84.2 /x. The shaft is 2.6-4. 5 m thick, straight, or, rarely, curved. Sometimes it is slightly thickened at or near the middle, sometimes no trace of a central tyle can be detected. The tyle is, when present, sometimes 1.4 /x more than the adjacent parts of the shaft in transverse diameter. The surface of the shaft is somewhat undulating and spiny. The spines are usually very minute; sometimes a few larger ones arise from the central tyle. The terminal anchors are 10-23 /x long, one fifth to one fourth of the whole spicule, and 14-36 m broad. The proportion of the length to the breadth of the anchors is 100 to 107-200, on an average 100 : 150.9. The anchor-teeth arise vertically from the ends of the shaft, are either strongly bent a short distance from their base and slightly curved in their distal and middle-parts, or curved with a radius increasing distally in a uniform manner. Their tips diverge. The teeth are sharp-pointed at the end, and attain a maximum breadth of about 4 n- The small micramphidiscs (Plate 103, figs. 27-29) are 16-38.7 n long, most frequently about 19.2, 26.8, and 34.2 /x.1 The shaft is straight or, rarely, some- what curved, 1.2-1. 9 n thick, spiny, and sometimes slightly thickened in or near the centre to a small tyle. The spines are generally very minute ; exception- ally one or two of the central ones attain a length of 1 p. The terminal anchors are similar to those of the large micramphidiscs, but narrower. They are 4.5- 10 m long, usually a little less than a third of the whole spicule, and 5.3-14 ^ broad. The proportion of the length to the breadth of the anchors is 100 to 96- 157, on an average 100 : 128.1. The nearest allies of the above sponge are Hyalonema ( Skianema ) aequatoriale and H. ( Thallonema ) geminatum described in this Report. From H. ( S .) aequa- toriale it differs chiefly by the absence of spheres and the smaller average size of the microhexactines and large micramphidiscs; from H. ( T .) geminatum by the absence of geminate macramphidiscs and differences in the shape of the small macramphidiscs, the micramphidiscs, and the pinules. 1 1 give these three numbers because the length frequency-curve pertaining to these spicules has three nearly equally important elevations. 390 HYALONEMA (THALLONEMA) GEMINATUM. THALLONEMA, subgen. nov. Species of Hyalonema of which the amphidiscs of one kind (the largest) have anchors which appear as if they were double, because some or most of their teeth bear from one to three simple branches. The collection contains one fragment of this subgenus. This belongs to a new species. Hyalonema (Thallonema) geminatum, sp. nov. Plate 103, figs. 37-62; Plate 104, figs. 1-14; Plate 105, figs. 1-14. There is in the collection one small fragment of this species. It was trawled in the Central Tropical Pacific at Station 4740 on 11 February, 1905; 9° 2.1' S., 123° 20.1' W.; depth 4429 m. (2422 f.); it grew on a bottom of dark gray Globigerina ooze; the bottom-temperature was 34.2°. Many of the anchor-teeth of the largest amphidiscs are provided with from one to three branches, which makes the anchors of these spicules appear doubled. To this the name refers. Shape a7id size. The fragment is an oval lamella, 50 mm. long, 34 mm. broad, and has a maximum thickness of 3 mm. The colour in spirit is light dirty brown. The skeleton. A dense fur, composed of the distal rays of superficial pinules, covers the intact parts of both faces of the lamella. Much smaller, probably canalar pinules are found in the interior. Besides the lateral rays of the super- ficial pinules the lateral rays of pentactine megascleres and paratangentially extending amphioxes are found in the superficial membrane. Amphioxes similar to the superficial ones, hexactine megascleres, and microhexactines occur in large numbers in the choanosome. The sponge possesses four kinds of amphi- discs:— large geminate macramphidiscs, ordinary large macramphidiscs, small macramphidiscs, and micramphidiscs. All these kinds of amphidiscs are abundant. Superficial pinules are, as above stated, found on both sides of the lamella. Those on the one side are very similar to those on the other. The only difference between them which I could detect is that the basal thickness of the distal ray appears to be in those of the one face (the dermal ?) on the whole slightly greater than in those on the other (the gastral ?). The dermal and gastral superficial pinules (Plate 103, figs. 58-62) are pentac- HYALGNEMA (THALLONEMA) GEMINATUM. 391 tine. The distal ray is straight and 178-270 ^ long, most frequently about 250 ix. It usually ends in a rather stout and sharp-pointed terminal cone (Plate 103, figs. 59-62). Exceptionally the tip is rounded (Plate 103, fig. 58). The basal thickness of the ray is 7-11 ix. Apart from small parts of it at the basal and distal ends, the ray is quite densely spined. The spines are for the most part nearly straight. Those arising from the middle-part of the ray are of considerable size, up to 30 n and more long. The maximum thickness of the distal ray, together with the spines, is 32-46 ix. The lateral rays are conical, blunt-pointed, spined, and 28-43 ix long. The small, probably canalar pinules are pentactine. The distal ray is straight, usually 90-110 ix long, and 4-6 n thick at the base. Its base and its sharp-pointed distal end-part are smooth; its middle-part bears very large, strongly divergent, sparse spines, which are curved, concave towards the tip of the ray. The largest spines are found in the proximal part of the spine-bearing region. The lateral rays are conical and 32-60 m long, generally 40-50 /x. The hypodermal and hypogastral pentadines have smooth, straight, and very blunt, conical rays. The proximal ray is 0.2-1 mm. long, and 7-22 ^ thick at the base. The lateral rays are 160-450 ix long. The hexadine megasderes are generally 0.8-1. 8 mm. in diameter and have smooth, blunt, conical rays 15-45 ix thick at the base. The superficial and choanosomal amphioxes are usually fairly straight, rarely markedly curved, and 0.4-2. 6 mm. long. The shorter ones, that is those under 1 mm. in length, are distinctly centrotyle with a tyle 1-4 \x more than the adjacent parts of the spicule in transverse diameter. The medium ones, that is those 1-1.5 mm. in length, have only a very insignificant tyle, not more than 1.5 ju thicker than the adjacent parts of the spicule. In the large ones, that is those over 1.5 mm. in length, there is hardly a trace of a central tyle. The microhexadines (Plate 103, figs. 39-48) are 37-120, usually 53-100 n in diameter (maximum diameter). Most of them have equal rays; in some two opposite rays are longer than the other four. The rays are 1.8-2. 2 /x thick at the base, conical, and finely pointed. The proximal part, about the half of the ray, is straight, the distal part curved- This curvature is either uniform, or, more frequently, at the point where the proximal straight part passes into the distal curved part greater than elsewhere. The total curvature is such that the directions (tangents) of the proximal and distal end-parts of the ray usually enclose an angle of about 120°. The rays bear very numerous, exceedingly minute spines, which give them the appearance of being rough. 392 HYALONEMA (THALLONEMA) GEMINATUM. Among the amphidiscs two main kinds can be distinguished morphologi- cally: — larger ones with relatively large anchors, and smaller ones with relatively medium-sized or small anchors. I consider the former as macramphidiscs, the latter as micramphidiscs. Among the macramphidiscs three subgroups can be distinguished morpho- logically:— a, large ones with short and broad anchors, some to most of the teeth of which are branched; b, middle-sized ones with short and broad anchors, and simple teeth; and c, smaller ones with long and broad anchors and simple teeth. These three macramphidisc groups are connected by transitional forms both morphologically and biometrically. The morphological connections be- tween b and c are macramphidiscs under middle size with anchors of medium length. The morphological connections between a and b are large macramphi- discs in which only one or two anchor-teeth are branched. As the length frequency-curve pertaining to the macramphidiscs in Figure 26 shows, there is a conspicuous enough depression separating biometrically the bulk of b from c; on the other hand the depression between the bulk of a and the bulk of b is very insignificant. Although the three subgroups of macram- phidiscs are thus rather closely connected both morphologically and biometri- cally, I think the difference between them sufficient for a separate description. The micramphidiscs are very various in size, their length ranging from 16- 92 /j.. They are, however, morphologically all very much alike. The length frequency-curve pertaining to them is, as the figure shows, exceedingly irregular and has no less than six low elevations in its left part (which pertains to the smaller forms) and one high elevation in its right end-part (which pertains to the largest forms). According to this one might divide these amphidiscs into two subgroups: — large micramphidiscs for those to which the simple high ele- vation in the right-hand end-part of the curve pertains, and small micram- phidiscs for those to which the irregular left-hand and central parts of the curve pertain. Since, however, there is but very little morphological difference between the former and the latter, I refrain from doing so. I accordingly distinguish four kinds of amphidiscs in this species: — 1, geminate, 2, large, and 3, small macramphidiscs; and 4, micramphidiscs. The geminate macramphidiscs (Plate 104, figs. 1-5, 8, 11, 12; Plate 105, figs. 1-14) are 210-360 m long, most frequently about 278 m- The shaft is 21-31 /x thick, straight or slightly curved, and usually quite smooth and simply cylindri- cal. Sometimes a large, terminally rounded spine or branch, 20-30 m long, arises from the middle-part of the shaft (Plate 105, fig. 3) . When such a spine is present Length of Amphidiscs (/*). i i !. ■o S' CL Fig. 26. — Amphidiscs. Macramphidiscs generally Geminate ^ Large > Macramphidiscs Macramphidiscs Small ) 394 HYALONEMA (THALLONEMA) GEMINATUM. the shaft is particularly strongly bent, convex towards the spine. The terminal anchors are 72-100 ^ long, a fourth to a third of the whole spicule, and 175-200 n broad. The proportion of the length to the breadth of the anchors is 100 to 182-257, on an average 100 : 223. The anchor is composed of from ten to fifteen teeth. The individual teeth are usually more strongly curved in their distal than in their proximal part. The extreme tips of the teeth are, if not widened to terminal discs ( vide infra), generally abruptly bent inward and convergent. A larger or a smaller number, most frequently about half, rarely all, of these teeth bear from one to three branches. Generally one anchor of the spicule is richer in branched teeth than the other. The branched teeth consist of a stem similar to an ordinary unbranched anchor-tooth, from the outer convex side of which from one to three branches arise. These branches are curved conformly with the stem from which they arise, concave towards the shaft, and usually end in oval flattened extensions, which appear as terminal discs. The end of the stem or main tooth, from which these branch-teeth arise, often also terminates with such an extension. The outer faces of the simple teeth and of the end-parts or terminal discs of the stem and the branches of the branched ones lie in a continuous surface ovoid in shape, which I take to be the inner face of the limit or wall of the living unit — in my opinion a single cell — within and by which the amphidisc is formed. As stated above, transitional forms with only one or two branched anchor-teeth (Plate 105, fig. 14) connect these geminate with the ordinary large macramphidiscs described below. The ordinary large macramphidiscs (Plate 104, figs. 6, 7) are 133-271 m long, most frequently about 198.5 and 204.2 n. The shaft is 15-26 n thick, generally straight, cylindrical, and smooth, sometimes slightly bent, and occasionally provided with one stout blunt spine about 20 ^ long. When such a spine is present the shaft is always bent as in the geminate macramphidiscs. The termi- nal anchors are 48-105 n long, a third to two fifths of the whole spicule, and 1 15— 203 m broad. The proportion of the length to the breadth of the anchors is 100 to 169-274, on an average 100 : 225.5. The anchor is composed of from eight to eleven teeth. The number of teeth in the two anchors of the same spicule is not always the same. The teeth of the opposite anchors often, but by no means always, alternate. The individual teeth arise nearly vertically from the ends of the shaft, are straight or only slightly curved in their basal part, but strongly curved in their distal part. The outer band-shaped portion of the tooth attains, in the larger forms, a maximum breadth of 25-29 m- Its distal end is rounded and abruptly bent inward so that the tips of the teeth HYALONEMA (THALLONEMA) GEMINATUM. 395 become strongly convergent, the distance between opposite teeth being 6-20 n, rarely as much as 32 n, less than the (maximum) breadth of the anchor. The small macramphidiscs (Plate 104, figs. 9, 10, 13, 14) are 88-153 m long, most frequently about 112 A good many of the largest, that is of those 136— 153 fi long, have anchors of only medium length and are consequently transi- tional to the large macramphidiscs above described. The shaft is straight, cylindrical, and 6-12 n thick. The terminal anchors are 50-72 n long, a third to half of the whole spicule, and 70-130 n broad. The proportion of the length to the breadth of the anchors is 100 to 146-183, on an average 100 : 161.8. The anchors are composed of from ten to sixteen teeth. Roughly speaking, the number of teeth is in inverse proportion to the size of the spicule. The teeth of the two anchors of the same spicule are often, but by no means always, situ- ated alternately. The individual teeth are generally quite uniformly curved through a quarter of a circle and abruptly bent inward at the end, so that their tips are strongly convergent. The outer band-shaped part of the tooth attains its maximum breadth in its distal portion, and is here 12-18 m broad. The end is broad, rounded off, sometimes nearly truncate. The micramphidiscs (Plate 103, figs. 37, 38, 49-57) are 16-92 n long, the larger ones, to which the conspicuous elevation near the right-hand end of the curve pertains, most frequently about 76.5 n long. The shaft is straight or only very slightly curved, and 0.7-5 ^ thick. It is simply cylindrical or slightly thickened at or near the middle to a central tyle, 0.3-0. 6 n, rarely as much as 1.5 ii, more than the adjacent parts of the shaft in transverse diameter. Centro- tyle forms are more frequent among the larger than among the smaller micram- phidiscs. A larger or smaller number of small spines are scattered over the whole of the shaft. In the centrotyle forms the spines arising from the central tyle are usually larger than the others. The terminal anchors are 3.5-24 n long, that is one fifth to two fifths of the whole spicule, and 5.5-30 n broad. The proportion of the length to the breadth of the anchors is 100 to 100 200, on an average 100 : 150.5. The anchors of the larger forms are on the whole relatively broader than those of the smaller. The anchor is composed of a considerable number of teeth; in one 24 n broad I counted eighteen. The individual teeth are, in the larger micramphidiscs, up to 5 m broad, and pointed at the end. Besides the regular micramphidiscs above described I observed a few irregu- lar micramphidiscs with terminal anchors on one side much longer than on the other. In these anchors the tips of the anchor-teeth lie in an oblique plane enclos- ing an angle of about 45° with the axis of the shaft. The longest part of one 396 HYALONEMA (THALLONEMA) GEMINATUM. anchor lies on the same side of the shaft as the shortest side of the other. The dimensions of a typical amphidisc of this kind are: — total length 22 /*; thick- ness of shaft 1.5 m! length of the longest and shortest parts (sides) of the anchors respectively 7.5 m and 4 breadth of anchors 9 n. The nearest allies of the above sponge are Hyalonema ( Skianema ) aequa- toriale and H. ( S .) umbraculum described in this Report. From both it is distinguished by the possession of large geminate macramphidiscs and small, long-spined canalar pinules, and by other differences in the spiculation. IV. LIST OF STATIONS Station Date Position Lat. Long. Tempi Sur- face srature Bot- tom Depth (fath- oms) Bottom 3363 26 Feb., 1891 N. 5 43 W. 85 50 83 37.5 978 White Globigerina ooze. 3376 4 March, 1891 N. 3 9 W. 82 8 78 36.3 1132 Gray Globigerina ooze. 3681 (A. A. 2) 27 Aug., 1899 N. 28 23 W. 126 57 66 34.6 2368 Red clay, light brown volcanic ooze. 3684 (A. A. 17) 10 Sept., 1899 N. 0 50 W. 137 54 79 — 2463 Light yellow-gray Globigerina ooze. 3685 (A. A. 25) 14 Sept., 1899 S. 8.48 W. 139 48 80 38 830 Globigerina and volcanic mud and fragments. 3689 (A. A 134) 28 Oct., 1899 S. 18 06 W. 142 24 79 37.6 807 Fine coral-sand and manganese nod- ules. 4621 21 Oct., 1904 N. 6 36 W. 81 44 79 40.5 581 Green mud and rock. 4622 21 Oct., 1904 N. 6 31 W. 81 44 81 — 581 Green sand and rock. 4630 3 Nov., 1904 N. 6 53 W. 81 42.5 81 40.5 556 Green sand, large Globigerina. 4631 3 Nov., 1904 N. 6 26 W. 81 49 82 38.0 774 Green sand. 4641 7 Nov., 1904 S. 1 34.4 W. 89 30.2 74 39.5 633 Light gray Globigerina ooze. 4642 7 Nov., 1904 S. 1 30.5 W. 89 35 74 48.6 300 Broken shells and Globigerina. 4649 10 Nov., 1904 S. 5 17 W. 85 19.5 70 35.4 2235 Sticky gray mud. Very few Globigerina. 4651 11 Nov., 1904 S. 5 41.7 W. 82 59.7 66 35.4 2222 Sticky fine gray sand. 4656 13 Nov., 1904 S. 6 54.6 W. 83 34.3 69 35.2 2222 Fine green mud mixed with gray ooze, mineral particles. Sponge spicules, many diatoms. 4662 16 Nov., 1904 S. 11 13.8 W. 89 35 69 35.2 2439 Brown Radiolaria ooze, manganese nodules. 4672 21 Nov., 1904 S. 13 11.6 W. 78 18.3 65 35.2 2845 Fine green clay; infusorial earth full of diatoms. 4685 10 Dec., 1904 S. 21 36.2 W. 94 56 72 35.3 2205 Dark brown clay. 4695 23 Dec., 1904 S. 25 22.4 W. 107 45 74 — 2020 Fine light brown ooze. 4701 26 Dec., 1904 S. 19 11.5 W. 102 24 72 35.3 2265 Dark brown chocolate clay. 4709 30 Dec., 1904 S. 10 15.2 W. 95 40.8 72 35.3 2035 Light gray Globigerina ooze. 4711 31 Dec., 1904 S. 7 47.5 W. 94 5.5 75 35.3 2240 do. 4721 15 Jan., 1905 S. 8 7.5 W. 104 10.5 75 — 2084 Light brown Globigerina ooze. 4732 21 Jan., 1905 S. 16 32.5 W. 119 59 79 34.8 2012 Light gray Globigerina ooze. 4736 23 Jan., 1905 S. 19 0.4 W. 125 5.4 81 34.8 2289 Dark brown chocolate mud. 4740 11 Feb., 1905 S. 9 2.1 W. 123 20.1 81 34.2 2422 Dark gray Globigerina ooze. 4742 15 Feb., 1905 N. 0 3.4 W. 117 15.8 77 34.3 2320 Very light fine Globigerina ooze. 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