.. EXPÉDITION ANTARCTIQUE BELGE RÉSULTATS DU VOYAGE DU S. Y. BELGICA EN 1897-1898-1899 SOUS LE COMMANDEMENT DE A. DE GERLACHE DE GOMERY RAPPORTS SCIENTIFIQUES PUBLIES AUX FRAIS DU GOUVERNEMENT BELGE, SOUS LA DIRECTION DE LA COMMISSION DE LA BELGICA ' ~ " — — = —^^M LD 1 ^^^= r-^ WHOI 11 m i-n □ '- — — - □ ^1 ^^^^« □ ! CD ZOOLOGIE SCHIZOPODA AND CUMACEA H. J. HANSEN - AN VERS IMPRIMERIE J.-E. BUSCHMANN REMPART DE LA PORTE DU RHIN I908 Composition de la Commission de la " Belgica" (Instituée par arrêté royal du 4 Décembre i8çq.) BUREAU Président : M. Van Beneden, Edouard, professeur à l'Université de Liège, membre de l'Académie royale de Belgique. Vice-Président : M. A. de Gerlache de Gomery, conservateur au Musée royal d'Histoire naturelle, promoteur et commandant de l'Expédition antarctique belge. Secrétaire : M. G. Lecointe, directeur scientifique à l'Observatoire royal de Belgique, commandant en second de l'Expédition antarctique belge. MEMBRES : MM. Arctowski, assistant à l'Observatoire royal de Belgique, membre du personnel scientifique de la « Belgica ». le Dr Cook, médecin de l'Expédition antarctique belge. Dobrowolski, membre du personnel scientifique de la « Belgica i. Racovitza, sous-directeur du Laboratoire Arago de Banyuls.-sur-Mer, membre du personnel scien- tifique de la « Belgica » . Donny, lieutenant-général, aide-de-camp du Roi. Du Fief, secrétaire-général de la Société royale belge de géographie. Dupont, directeur du Musée royal d'histoire naturelle, membre de l'Académie royale de Belgique. Durand, directeur du Jardin botanique de l'Etat, membre de l'Académie royale de Belgique. Lagrange, Ch., professeur à l'Ecole militaire, directeur honoraire à l'Observatoire royale de Belgique, membre de l'Académie royale de Belgique. Pelseneer, professeur à l'Ecole normale de Gand, membre de l'Académie royale de Belgique. Spring, professeur à l'Université de Liège, membre de l'Académie royale de Belgique. Stainier, professeur à l'Université de Gand. MEMBRES DÉCÉDÉS : MM. le Lieutenant-général Brialmont, membre de l'Académie royale de Belgique (déc. en juillet igo3). Crépin, directeur du Jardin botanique de l'Etat, membre de l'Académie royale de Belgique (décédé en mai igo3). DE la Vallée-Poussin, professeur à l'Université de Louvain, membre de l'Académie royale de Belgique (décédé en avril igo3). Errera, Léo, professeur à l'Université de Bruxelles, membre de l'Académie royale de Belgique (décédé en août igo5). Lancaster, directeur scientifique à l'Observatoire royal de Belgique, membre de l'Académie royale de Belgique (décédé en février 1908). Renard, professeur à l'Université de Gand, membre de l'Académie royale de Belgique (décédé en juillet igo3). SCHIZOPODA AND CUMACEA BY H. J. HANSEN 1 R 57 Sorti des presses de J.-E. BUSCHMANN, Anvers le 25 Novembre 1908. SCHIZOPODA AND CUMACEA H. J. HANSEN I. - The Order EUPHAUSIACEA (') The material comprises two adult species, one of which is new to science, a few very young or not fully developed spécimens of two other species, and a number of larvae belonging to two species. It is often difficult and not infrequently impossible to détermine half-grown spécimens and especially larval forms vvhen tolerabl}^ complète séries of stages are not to hand, and the difficulties become increased when the material is proportionately scanty, not containing several of the forms inhabiting the sea in question. Fortunately I am able to name nearly the whole material from the Belgica, but one species represented by two larval stages remains uncertain. I describe, however, and give analytical figures of ail larval stages in the collection, especially because the métamorphoses of the two species differ from one another and présent features differing in a very interesting way from the development of a species of the same genus workecl out by G. O. Sars in the Challenger report. A. — ADULT AND NEARLY HALF-GROWN SPECIMENS i. — Euphausia superba Dana In 1906 Holt & Tattersall made out that E. superba sensu G. O. Sars is the adult maie, E. Murrayi G. O. S. the adult female, E. antarctica G. O. S. the immature form of the same species, furthermore that E. glacialis Hodgson and E. australis Hodgson are to be cancel- led as synonyms to E. superba. I can fully confirm thèse statements. Occurrence. — Lat. 700 20' S., long. 85° 52' W., about twenty spécimens taken « dans une fente de la banquise antarctique, près de la surface, 27 décembre 1S98 »; nearly ail the spécimens are moderately large, but none really full-grown. — Lat. 70° 54' S., long. 890 18' W., about twenty spécimens from the stomach of Eobodon carcinophaga ; how common it must be is (1) The name Schizopoda is used in the title only because it is brief and still generally used ; the two orders Euphausiacea and Mysidacea are in reality far from closely related to each other. EXPEDITION ANTARCTIQUE BELGE seen from the remark : « Cette espèce fournit la nourriture presque exclusive des manchots et phoques ». Larval stages taken near the last station are described in the sequel. Distribution. — E. superba, established in i852, seems to live everywhere in the Antarctic Océan, as it has been taken by every expédition touching or exploiïng any part of thèse seas. Remarks. — The zoologist of the Belgica, Prof. Emile G. Racovitza, communicated me his notes on the spécimens from the first-named locality ; his observations are so interesting that thev ought to be given in extenso in his own words. « Les yeux sont noirs, les organes lumineux purpureus, le corps et les appendices transparents, incolores, laissant apercevoir l'intestin ruber ou brun foncé et le foie flavovirens. Une teinte violaceus pâle colore les jointures des pléopodes et la surface des branches des pléopodes, des uropodes et des antennules. Des chromatophores ruber sont distribués sur tout le corps de la manière suivante. Les cormopodes en ont une rangée sur la face externe, ceux des articles basilaires sont gros, tandis que ceux des longs articles distaux sont très petits. Les antennes sont couvertes de chromatophores. Le céphalothorax en a un groupe antérieur relié à un groupe postérieur par deux bandes latérales laissant -le milieu de la carapace incolore. Chaque segment abdominal en a un large groupe dorsal, et une traînée bien fournie court le long de la ligne médiane ventrale. Le telson possède des chromatophores du côté dorsal. » Ces animaux sont constamment en mouvement ; les pléopodes battent régulièrement d'avant en arrière pendant quelque temps, puis l'animal exécute quelques sauts. Les cormo- podes, avec leurs longues soies hérissées de poils, agissent comme un filet pour capturer les petits animaux et surtout les diatomées. De nombreux corps cylindriques de 164 p de dia- mètre et jusqu'à 5 mm. de longueur, de couleur blanche, flottent dans l'eau qui contient des Euphausia ; ce sont leurs fèces, formées surtout de débris de frustules de diatomées. » Les Euphausia se tiennent de préférence à quelques centimètres en dessous de la surface, dans les anfractuosités des plaques de la banquise, là où les diatomées sont abondantes. » Presque tous les exemplaires ont des infusoires parasites fixés sur les soies des pléopodes ou bien sur celles des exopodites des cormopodes. » 2. — Euphausia longirostris n. sp. iPl. I, figs. la— 1 c) The Belgica obtained the anterior half of an adult spécimen, but later I received several fine spécimens captured by the Swedish antarctic Expédition. E. longirostris is closely allied to E. spinifera G. O. Sars, but it is readily separated by the shape of the lappet of the first antennular joint. In E. longirostris this lappet is distally much narrower than the proximal part of the second joint and bifid, terminating in two triangular, acute, flat processes, while in E. spinifera the lappet is distalky not narrower than the proximal part of the second joint, and its terminal transverse margin has a row of spiniform teeth. The carapace agrées closely with that of E. spinifera as to the shape ol the dorsal crest, the existence of a small sublateral tooth from the front margin above the eye-stalks, SCHIZOPODA AND CUMACEA the place of the latéral denticle above a small incision in the lower margin, the submarginal furrow from the insertion of the latéral denticle to the base of the antennse, and the deep incision in the upper part of the hind margin, but the rostrum is still longer than in the last-named species, reaching nearly to the end of the antennular lappet, thus longer than in anv other species of the genus (or the order). The antennular peduncle has the characteristic lappet just described on the first joint, second joint is provided with a long, spiniform, almost horizontal process from the middle of its upper distal margin; the dorsal canna on the third joint is high. The abdomen has the third segment armed dorsally with a long, compressed, slightly decumbent process; fourth and fifth segment each with a moderately short, spiniform unpaired process ; ail three segments hâve the upper part of their posterior margin adorned with incisions nearly as in E. spinifera, but the epimera of the fifth segment are less produced posteriorly than in the latter species. A spécimen from the Swedish Expédition measures 28 mm. in length. Locality. — Lat. 56° 49' S., long. 640 3o' W.; depth of the sea 385o m., Jan. 16, 1898. The fragment was captured bv the sounding apparatus. 3. — Thysanoëssa macrura G. O. Sais (i883) (PI. I, figs. 2 a— 2 h iSS5. Thysanoëssa macrura G. O. Sars, Report Challenger Schizopoda. vol. XIII. p. 125, pi. XXIII, figs. 1-4. 1906. — — Holt & Tattersall, Ann. Mas. Nat. Hist., ser. 7, vol. XVII, p. 5. To this species I refer four immature spécimens; the largest spécimen measures 8 mm., the smallest only 5.y mm. in length. Figures 2, a — 2/ represent parts of the large spécimen, figs. 2 g — 2 h parts of the small one. The large spécimen agrées moderately well with the description and the figures given by Sars, but the présence of a small spiniform process at the outer end of the distal edge of the basai antennular joint — a feature being a remnant of a larval character — shows that the animal has not quite finished the development. The upper section of the eyes is small (fig. 2a); the rostrum (fig. 2 b) is a little shorter than in Sars' figure ; the céphalothorax possesses the latéral denticle; the sixth abdominal segment is slightly shorter than the sum ofthe fourth and the fifth (fig. 2e). Only one of the trunk-legs ofthe first pair is preserved, and it is unusually short (fig. 2d), with the penultimate joint slightly longer than the last ; the last joint is a little shorter than some of the setœ situated on its apex and its lower margin, and two of the last-named setre are strong and sparingly ciliated. The terminal part of the telson has acquired its final shape and armature (fig. 2/). The small spécimen (figs. 2 g — 2 h) shows some larval characters : it is in reality in the last larval stage, but it is dealt with hère for the sake of comparison. The rostrum is a little shorter than in the preceding spécimen, the process from the distal margin of first antennular joint is long, the antennular flagella are short and unjointed, and the telson must be described separa- tely. The most distal, tapering part of the telson is considerably shorter in proportion to its breadth and the movable flat spines are much narrower (fig. 2 h) than in the large spécimen, but the most essential différence is that a slender spine, ciliated along its inner margin and as long EXPEDITION ANTARCTIQUE BELGE as the fiât spine, is inserted laterally just in front of the latter, while it is absent in the following stage. The trunk-legs of first pair are long (fig. 2 g), much longer than the second pair and proportionately much longer than the corresponding leg in the large spécimen ; in thèse legs the last joint is siightly more than half as long as the penultimate joint. As a parallel it may be mentioned that Holt & Tattersall state that most of their spécimens — ■ from i3 to 28 mm. in length — had the first pair of legs much longer than in the spécimen figured by Sars, while in two spécimens thèse legs are only as long as in the types. The two remaining spécimens, which are respectively 7.7 mm. and 6.3 mm., hâve arrived at the same stage of development as the largest spécimen described. In both spécimens the préhensile legs are wanting. Localities. — Lat. 70°4i' S., long. go° 14' W., May 1, 1898, plankton VIII; one spéci- men. — Lat. 70°33' S., long. 89° 22' W., May 4, 1898, plankton IX; two spécimens (the types for my figures). — Lat. 700 o5' S., long. 83° 07' AV., August 3i, 1898, plankton ; one spécimen. Distribution. — Tins species is evidently widely distributed. Sars enumerates four localities more or less distant from Kerguelen, two places in the Antarctic Océan at the ice-barrier, and a place in the South Atlantic, south of B'uenos-Ayres. Holt & Tattersall had numerous spécimens from the Discovery, they « were taken both in the open sea and through holes in the ice » ; Stebbing mentions it from the Falkland Islands. B. — SPECIMENS IN THE LAST LARVAL STAGE (') 4. — Euphausia cn'stallorophias Holt & Tatt. (PI. I, figs. 3*-3<- 1906. Euphausia crystallorophias Holt & Tattersall. Ane. Mag. Nat. Hist., soi. 7, vol. XVII, p. 3. Three spécimens are to hand, the largest measuring 10 mm., the two others 9 mm. in length, but ail in the same stage of development. Mr. Holt kindly presented me with several spécimens of his E. crystallorophias, and the smallest of thèse is nearly 14 mm. A comparison with this spécimen gave the resuit that the three spécimens captured by the Belgica belong to the same species. Mr. Holt's young spécimen has not yet lost the spiniform process on the front margin of the basai antennular joint, but the telson has obtained the shape and armature found in adult spécimens. The spécimens from the Belgica hâve the antennular process mentioned at least as long as in Mr. Holt's spécimen, but the telson has a pair of long, slender spines inserted in front of the long, depressed, movable spines (fig. 3 c). The three spécimens agrée with E. crystallorophias in the shape and relative length of the joints in the antennular peduncles, in showing no trace of lappet on the basai antennular joint, in possessing very large eyes (fig. 3 a), in the shape of the rostrum, furthermore in the slenderness of the body, in the existence of a marginal tooth on the carapace, and in the relative length of the rami of the uropoda. (1) A single spécimen of Thysanoessa macrura, which ought to hâve been dealt with under this heading, is described above together with a more developed spécimen. SCHIZOPODA AND CUMACEA In my spécimens the antennular flagella are extremely long, as long as the sum of the céphalothorax and the two anterior abdominal segments. The maxillipeds and four anterior pairs of legs are well developed, but the legs of fifth pair are very short, the endopod only as long as the exopod and about as long as the penultimate joint of the maxillipeds. Occurrence.— Lat. 69° 5g' S., long. 82° 3g' W., September 3, 1898, plankton ; two spécimens. — Lat. 700 09' S., 82°35'W., November 11, 1898, plankton; one spécimen (type for the figures). Distribution. — This species was taken by the Discovery through holes eut in the ice, and has not been recorded from any other expédition. C. - - SPECIMENS IN INTERMEDIATE LARVAL STAGES Larvae of Euphausia superba Dana (PL I. figs. 4 a — j m . From a single station a good number of spécimens of the same species are to hand. The larvae are in four stages, and it is necessary to describe each stage separately. Stage A (figs. 40 — 4e). — A spécimen measures 4.5 mm. from the margin of the rostrum to the tip of the telson. The carapace is without posterior dorsal process or marginal teeth. The rostrum is a very large and broad plate (fig. 4 a) with the front margin semicircular ; it covers abouth three-fourths of the inner part of the basai antennular joint. The large eyes are not marked off from the stalk — but the préservation is not good and therefore the aspect given in fig. 4 a is only approximate. The outer part of the distal end of first antennular joint is produced into a very long process reaching to the end of third peduncular joint and armed with numerous spinules along its inner margin. The inner flagellum is considerably shorter than the third joint of the peduncle and longer than the outer flagellum ; both flagella are unjointed and terminate in setae ; several plumose setae are found along the inner side of the joints of the peduncle, especially on the third joint. The antennae hâve both rami subequal in shape and length, each of them about as long as the sum of the two distal joints of the antennular peduncle and terminating in a bundle of long setae. The mandibular palp is a small conical joint. The maxillipeds (fig. 46) hâve the endopod three-jointed, somewhat longer than the exopod but considerably shorter than the broad lamellar basai part of the appendage. Five pairs of legs are somewhat developed : the endopods are nearly sausage-shaped, not very distinctly divided into joints, terminating in a short setae, and about twice as long as the exopods (fig. 4 c) ; the legs hâve a vestige of the branchia at the base ; fifth pair are somewhat shorter than the other pairs which are subequal in length and somewhat shorter than the maxillipeds. Four pairs of pleopods are scarcely as long as the height of their segments ; the exopods are marked off from the peduncles, sausage-shaped, without bristles ; the endopods are still wanting. Fifth pair of pleopods scarcely visible. Sixth abdominal segment a little longer than broad (fig. 4 d). The uropoda scarcely half as long as the telson, far from reaching its latéral spines; the exopod is somewhat longer than the endopod, and both rami are furnished with long setae. The telson (figs. 4 d and 4 e) is three and a half times longer EXPEDITION ANTARCTIQUE BELGE than sixth segment, widening from the base to near the end where it is almost twice as broad as at the base ; a latéral spine is found somewhat behind the middle, and thèse spines hâve each two secondary spinules at some distance from the base. The posterior margin has its major portion straight, transverse, with seven spines ; towards each side the margin bends suddenly obliquely forwards, and each oblique postero-lateral part has three spines. The seven spines hâve a row of fine spinules along each margin ; the médian spine is moderately short, while the others are gradually longer outwards, those of the fourth pair being not full\T twice as long as the médian spine. The three pairs of postero-lateral spines are characteristic ; the inner spine is very long, a little longer than the next and nearly twice as long as the third which is almost as long as the outer pair of posterior spines described ; ail three pairs hâve at a good distance from the tip a small, conspicuous, dorsal spine, and the two long pairs hâve numerous spinules along the inner margin between its base and the dorsal spine men- tioned, while their outer margin is glabrous ; the shorter outer pair hâve only one or two spinules on the inner margin. Stage B (figs. \f- — 4 //). — The spécimen drawn measures 6 mm. Céphalothorax, eves and antennae nearly as in stage A. The process on the basai antennular joint does not reach the end of the third joint; the flagella are subequal in length and a little longer than the third joint, but still unjointed (fig. 4/). The mandibular palp is moderately short, nearly sausage- shaped, scarcely divided into joints and without setse. The maxillipeds hâve the endopod nearly twice as long as the exopod, three-jointed. The five pairs of legs hâve the endopods distinctly divided into the final number of joints and are furnished with setae ; the four anterior pairs are nearly twice as long as the maxillipeds, fifth pair are a little shorter ; the branchiae are feebly developed. Ail pleopods hâve the exopods long and furnished with setae ; the endopods are small. Sixth abdominal segment (fig. 4^) about half as long again as broad, the uropods slightly more than half as long as the telson, not reaching its latéral spines, and the exopod longer than the endopod. The telson is not three times longer than the sixth segment and not fully three times as long as broad, thus conspicuously narrower than in stage A, but the armature and relative length and breadth of its spines are nearly as in that stage. Stage C (fig. 4/). — A spécimen measures 7 mm. The rostral plate is a little narrower than before ; the eyes are well marked off from the stalk. The inner antennular flagellum is slightly shorter than the outer, as long as the sum of the two distal joints of the peduncle ; both flagella are indistinctly divided into joints. The rami of the antennae are still subequal in breadth, but the exopod is a little shorter than the endopod. The mandibular palp is three- jointed, with a terminal bristle. The maxillipeds hâve the endopod somewhat longer than in the preceding stage, but it has not acquired its full number of joints and is much shorter than first pair of legs. The five pairs of legs look essentially as in the adults, the first pair reaching the end of the second antennular joint, the fifth pair (in which the part beyond the fourth joint is still rather short) having their end situated vertically below the posterior half of the eyes, but the branchiae are still somewhat feebly developed. The pleopods hâve the endopod considerablv longer than in the preceding stage, but still only half as long as the exopods. Sixth abdominal segment and telson as to shape intermediate between stage B and stage D ; the uropods reach to the latéral spines of the telson, and their rami are equal in length. The telson (fig. 4 i) has still seven spines on the posterior margin, but they differ less from each other as to length. The three postero-lateral spines hâve still preserved their armature, but the inner spine has SCHIZOPODA AND CUMACEA now its proximal half depressed and very much broader than before though not fully as broad as in the next stage, and the outer spine is proportionately somewhat shorter than in earlier stages. Stage D (fig. 4^ — 4m). — The spécimen drawn measures 7.5 mm. The rostral plate (fig. 4 k) is conspicuously narrower in front than in stage A ; the eyes are well defined. The antennulae are more developed ; the process from the end of first peduncular joint does not reach the end of the third joint ; the inner flagellum is considerably longer than the sum of the two distal joints of the peduncle and somewhat shorter than the outer flagellum ; both flagella are divided into five to seven joints. The antennae still nearly as in the preceding stage ; the exopod a little shorter and broader than the endopod. The mandibular palp and the endopod of the maxillipeds proportionately a little longer than in stage C. The trunk-legs are well developed. The pleopods are well furnished with setse ; their endopod is more than half as long as the exopods, with the secondary articulated lobe developed. Sixth abdominal segment (fig. 4 /) nearly twice as long as broad ; its uropods reach a little beyond the latéral spines of the telson. The telson is between two and a half and two times as long as the sixth segment and a little more than three and a half times as long as broad ; its posterior margin is considerably shorter than in earlier stages and has only five spines which are nearly equal in length (fig. 4 m) ; each postero-lateral margin is somewhat longer than before, its outer spine is shaped as in earlier stages but comparatively a good deal shorter, the second spine has preserved its shape and armature, while the inner spine is flattened and very broad in the proximal half, the spine being only a little more than four times as long as broad, and the spinules along the proximal half of its inner margin are lost. The following stages are not represented in the collection. I am sure, nevertheless, that the référence of the stages described to E. superba is correct. A view on Sars' figures of this species and especially of the immature spécimen of E. superba established by him as E. antarctica shows that especially in the fifth pair of legs the sum of the three joints beyond the vertical articulation is short in proportion to the sum of the joints before the « knee » ; this proximal part of the posterior legs is in reality longer in E. superba in proportion to céphalothorax than in any other species of the genus, and the last larval stage just described shows the same ; it may be added that the two posterior pairs of legs when directed forwards hâve the vertical articulation just below the eyes as in Sars' figures of E. Murrayi and E. antarctica (both synonyms to E. superba). Locality. — Lat. 700 33' S., long. 890 22' W., May 4, 1898, plankton ; many spécimens. Laiva of Euphausia sp. (PI. II, fiys. I a— i f Stage A (figs. 1 a — 1 c). — Length of my single spécimen 6.2 mm. According to the degree of development of telson and uropoda this spécimen agrées with stage C of E. superba, but its antennae and especially its antennulae are much more developed while the fourth and especially the fifth pair of legs are much less developed than in that animal. The carapace has a well developed latéral denticle ; the rostral plate (fig. la) is subtriangular and rounded in front. 11 R 57 EXPEDITION ANTARCTIQUE BELGE The antennulse hâve the process of first peduncular joint very long, reaching almost to the end of the peduncle ; the flagella are extremely long, measuring 2.4 mm., not fully two and a half times as long as the peduncle, subequal in length and distinctly jointed. The antennse hâve the endopod more than twice as long as the exopod, sausage-shaped, unjointed ; the exopod has to a certain degree acquired the final shape with setae along the inner and the terminal margin. The mandibular palp is moderately short, feebly jointed, without bristles. The maxillipeds and anterior pair of legs essentially as in the adults ; third pair are somewhat shorter, fourth pair hâve the endopod only half as long as in the third pair, and the endopod of fifth pair is very short, nearly rudimentary. The pleopoda developed nearly as in stage D of E. superba. Sixth abdominal segment slender, more than twice as long as broad. Telson slender, four times as long as broad ; the degree of development and armature nearly as in E. superba stage C, and small spécifie différences in the spines may be seen on the figures. Stage B (figs. 1 d — 1 /). — Length of one ofthe two spécimens 8.8 mm. The armature of the telson is less reduced than in stage D of E. superba, but in several other characters the animais are much more developed. The antennulœ hâve still the process from the basai joint nearly as long as the two following joints ; the flagella are long, but their terminal part is lost. The antennaa hâve both the squama and the flagellum sh'aped nearly as in the adult. The mandibular palp is three-jointed, with a very long terminal seta. Fourth pair of legs still considerably shorter than second (third pair are lost), and fifth pair are nearly rudimentary. Sixth abdominal segment somewhat more than twice as long as broad (fig. 1 e) ; the uropoda reach a little beyond the latéral spines ofthe telson. The telson is slightly more than twice as long as the sixth segment and five times as long as broad, thus very narrow ; the posterior margin is a little shorter than in stage A and its latéral pair of spines are somewhat reduced in size (fig. 1 /) ; the postero-lateral margins are considerably longer than in stage A and besides considerably concave ; the inner spine has its proximal third fiât and very expanded ; both this spine and the next are much longer than in stage A while the outer spine has its former length. Judging from many particulars I think that the two stages (three spécimens) described belong to the same species, but I am not able to point out the adult species to which thèse larv?e belong. The length of the process of the basai antennular joint, the high development of the antennular flagella and the slenderness of the abdomen ma}- induce one to refer them to E. crystallorophias, but a comparison between stage B and the above-mentioned animais referred to E. crystallorophias shows that the eyes are considerably smaller in the larvae of stage B than in the last-named animais, though they differ little from each other in length, and the différence as to the eyes is so considérable that the référence to E. crystallorophias must be abandoned. Localities. — Lat. 700 41' S., long. 900 14' W., Ma)* 1, 1898, plankton ; one spécimen (stage A). — Lat. 7i°i5' S., long. 870 27' W., May 21, 1898, plankton; two spécimens (stage B). D. — SOME MORPHOLOGICAL REMARKS ON THE DEVELOPMENT IN EUPHAUSIA It is pointed out in the description of stage A of Euphausia sp. that this larva has the telson developed as stage C of E. superba, while its antennular flagella is widely more developed, SCHIZOPODA AND CUMACEA its last pair of legs much less so than in the last-named form. This shows that there is considérable différence between the development in thèse two species of the same genus. In his standard work on the Euphausiacea of the Challenger, G. O. Sars fills two plates (pi. XXIX and XXX) with figures illustrating the development of his Euphausia pellucida, and the description of the larval stages occupy nearly nine pages. He thinks that the deve- lopment of the members of this order (which he regards as a family) is so uniform that he gives short diagnoses « of each of the principal stages peculiar to the development of the Euphausiida: » ; thèse stages he names Nanplius stage, Metanauplius stage, Calyptopis stage, Fui alui stage, Cyrtopia stage and Post-larval stage; it may be added that in the description of E. pellitcida he has three subdivisions of the Furcilia stage and two of the Calvplopis stage. And let us now take two examples for comparison between a couple of his stages and animais from the Belgica. In the diagnosis of the Furcilia stage we find (p. i5o) : « Anterior pairs of legs and pleopoda successively developing », and in his description of the last Furcilia stage of E. pclluada (p. idj) : « In this stage ail the pleopoda hâve become developed, and act in the living animal as true swimming organs. On the trunk the second pair of legs hâve become articulated, though they are still much smaller than the first, and behind it a few minute bud-like projections may be seen, apparently representing two additional pairs of legs, besides the first trace of the gills. » On pi. XXX, fig. 3 and fig. 40 represent respectively the antennula and the telson (and uropod) of the last Furcilia stage, and thèse figures agrée completely with the shape of the same organs in stage C of E. superba. But in the last Furcilia stage even the second pair of legs are still small and the following pairs only bud-like, while in stage C of E. superba ail five pairs of legs look essentially as in the adults, those of the fifth pair being so long that their end is situated vertically below the posterior half of the eyes. Consequently thèse larva? of the two species differ from each other in such an important point as the development of the legs, while they agrée in most other features. In the description of his first Cyrtopia stage of E. pellitcida Sars says (p. i57-i58). « The character distinguishing most prominently this stage from those preceding it, is the total change in structure and function of the antennas Of the two branches, the one has assumed the character of the scale, the other of the flagellum. » According to this description and his fig. 8 on pi. XXIX and fig. 7 on pi. XXX his larva agrées in this respect with stage A of my Euphausia sp., but further comparison shows that in my larva the trunk-legs are considerably more, the telson much less developed than in Sars' animal, as seen on his fig. 8 on pi. XXIX and fig. 41 on pi. XXX. The features pointed out show that there is much différence between the development of the three species of the same genus : when a set of organs are similarly developed in larvae of two species, other organs are either considerably more or much less developed in one of thèse larvae than in the other. Therefore it may be difficult to refer several larval forms to the Furcilia or Cyrtopia stages as they are defined by Sars. But our knowledge of the development of the species of this order is still in its infancy. EXPEDITION ANTARCTIQUE BELGE II. - The Order MYSIDACEA The collection contains two species. Both were new when handed over to me, but one of them has been described by E. W. L. Holt & W. M. Tattersall in their « Preliminary Notice of the Schizopoda collected by H. M. S. Discovery in the Antarctic Région (Ann. Mag. Nat. Hist., ser. 7, vol. XVII, 1906), and in the same paper the authors mention and name the other species, but do not describe it. Both species hâve received the names proposed by me ; when Mr. Holt in io,o5 visited Copenhagen I showed him the figures inserted in this paper and a number of spécimens of both species secured by the Swedish antarctic Expé- dition, and with his usual courtes)7 he accepted the names already chosen by me, viz. Pseudomma Bclgicœ and Mysis maxima. A short time after Prof. H. Coutière worked out and published his report on the Decapoda and Schizopoda from Dr. F. Charcot's antarctic Expédition ; he described and gave twenty figures of Mysis maxima, and established a new genus, Antarctomysis, for its réception. Fortunately the figures of this form drawn by me before Coutière's report was published will, I hope, be a useful supplément to the représentation given by the able French author. 1. — Pseudomma Belgicae (Hansen, MSS.), Holt & Tatt. (PL II, figs. 2 a— 2 c) 1906. Pseudomma Belgica Holt & Tattersall, Ann. Mag. Nat. Hist.. ser. 7. vol. XVII, p. S. From the Belgica only a single immature female is to hand, measuring 16. 5 mm. from the front margin of the ocular plate to the tip of telson ; the figures are drawn from this spéci- men. But from the Swedish antarctic Expédition I hâve a very large number of spécimens, and in the following I take them somewhat into considération, but the figures illustrating some variation must be postponed to the report on the Swedish Expédition. The species is closely allied to P. roseum G. O. S., P. affine G. O. S. and P. Sursit YVilL- Suhm; the main différences are found in the eye-plates, the antennal squama and the telson. The eye-plates are completely coalesced, slightly cleft in front, forming a somewhat subqua- drangular laterallv rounded plate which is less or more depressed at the médian Une, and the portion at each side of this longitudinal excavation is frequently raised towards the front margin where it in this case is produced in a feeble or very conspicuous angular protubérance; the margin of the eye-plates is otherwise completely smooth, without vestige of any serration. The antennal squama three and a half to nearly four times as long as broad ; its rounded apex extends slightly or at most a little beyond the tip of the marginal spine which is well developed. The telson is sometimes not far from twice as long as broad (fig. 2 b), frequently somewhat shorter and broader at the base ; its end is broadly rounded with three pairs or rather often only with two pairs of long spines (') and a pair of feathery setae ; each latéral margin has sometimes five, frequently six, seven or eight spines. I 1 1 Holt & Tattersall say that the apex has four pairs of spines, but I never found more than three pairs of long terminal spines, while a fourth pair of considerably shorter spines are inserted at the end of the latéral margin (corap. fig. 2 c). SCHIZOPODA AND CUMACEA i3 Length of an adult maie from the Swedish Expédition 27 mm., but the females are smaller, even rarely reaching the length given by Holt & Tattersall, viz. 23 mm. Colour. — On the colour of the spécimen taken by the Belgica the following note was made : « translucide incolore avec taches rougeâtres irrégulières. Estomac purpureus. » Locality. — Lat. 710 19' S., long. 870 37' AV., May 28, 1898, swab ; one spécimen. Distribution. — ■ The spécimen described by Holt & Tattersall was taken at lat. 780 25' 40' S., long. i65° 3g' 6' E. — I am inclined to think that Sars has seen a spécimen, which he referred to P. Sarsii Will.-Suhm ; he writes (Challenger, p. igi) : « A single and much larger, though rather mutilated spécimen, apparently of the same species was taken in the Antarctic Océan lat. 65° 42' S., long. 7g0 4g' E.; depth 1675 fathoms. » Unfortunately this spécimen seems to be lost, as I hâve looked for it in vain in the British Muséum (Nat. Hist.). 2. — Antarctomysis maxima (Hansen, MSS.), Holt & Tatt. PI. II. figs. 3a-3f»! 1906. Mysis maxima Holt & Tattersall, Ann. Mag. Nat. Hist.. ser. 7, vol. XVII, p. 11. 1906. Antarctomysis maxima Coutière, Expéd. antarct. Française, Crust. Schizop. et Décap , p. 1, figs. 1-20. The genus Antarctomysis established by Prof. Coutière is adopted hère, because it is founded on structural features équivalent with those applied for subdividing into gênera the large genus Mysis in the sensé adopted by G. O. Sars in his monograph of the Norwegian Mysidae. Gradually the suborder Mysida has been divided into so many often very closely allied gênera, that it would be useful to undertake a revision of the classification with the intention to reduce a good number of the gênera to subgenera of various main gênera in order to get a better view of the natural relationships of the species and gênera. The French author has given a diagnosis of the new genus. The material from the Belgica comprises three female spécimens, two of which are large while the third is less than half-grown. The Swedish Expédition has captured a good number of both sexes of this species, and besides many spécimens of an other closely allied but sharply defined species, for which I propose the name A. Ohlinii n. sp., in honour of Dr. A. Ohlin, the late Swedish Zoologist who wrote several useful papers on arctic and Patagonian Malacostraca and was the leading Zoologist of the Swedish antarctic Expédition. The main différences between the two gigantic species shall be pointed out hère, but a more spécial treatment of A. Ohlinii and of the maie of A. maxima must be postponed till the report of the last-named Expédition. Female of A. maxima. — The carapace is anteriorly somewhat produced into a moderately short, triangular, acute rostral plate, the distal part of which is somewhat concave and bent a little downwards (figs. 3a and 3 b). The front latéral margin of the carapace is subvertical and 'a little concave (fig. 3 b) ; the last thoracic segment and the posterior dorsal part of the penultimate segment are left uncovered by the carapace. The eye-stalks and eyes are considerably depressed ; seen from above (fig. 3a) the eyes look essentially outwards, occupying not only the front end but the major part of or nearly the whole outer margin of the stalk, so that the inner margin of the stalk itself is much or several times longer than its outer free margin i4 EXPEDITION ANTARCTIQUE BELGE behind the eye. The antennal squama is shaped nearly as in Michtheimysis mixta, lanceolate, long and very narrow, seven times or more longer than broad, closely set with setœ along both margins ; a distal short part is marked off by a transverse suture. Left mandible (fig. 3 c) has the molar process short with its end eut off obliquely and even a little concave behind (fig. 3 e) ; the second joint of the palp is more than twice as long as broad (fig. 3d). The maxillulse (fig. 3/) do not présent any aberration worth mentioning from those in Macromvsis ftexiiosa ; my figure shows the constituting éléments, but it may be pointed out that the basai joint itself and the major part of the second joint as situated on the upper surface are hidden when the maxillula is seen from below, and they are therefore indicated by dotted Unes. The maxillae (fig. 3 g) differ from those of M. flexuosa especially in the shape of the terminal joint; this joint is so much expanded inwards that it is considerably broader than long, more than half of its distal margin is nearly straight, and most of this margin is beautifully adorned with a close row of ver)' characteristic setse. The figure shows the constituting éléments, viz. the chitinous plates and two membranous areas — the latter are marked by uniformly greyish shading — but a description is omitted, because the lettering and the explanation of the plates may be sufficient for the morphological understanding. The maxillipeds (fig. 3 h) agrée closely with those pf M. flexuosa, differing from those of M. mixta in various minor particulars, especially in having the lobe from the fourth joint short, while it is long in M. mixta. The first pair of legs (fig. 3 i) are very similar to those of M. flexuosa. The telson is in large spécimens (fig. 3 /) a little more than three times as long as broad, decreasing somewhat but not gradually in breadth from near the base to a little in front of the end, where it gradually becomes slightly broader; the incision, which occupies one-fourth of the total length, is narrow in the proximal half, narrowing strongly in its distal, feebly in the proximal half. The outer margin of the telson is armed with a very large number of small spines, the end of each distal lobe terminâtes in a rather small but strong spine (fig. 3 m), and the margins of the incision are furnished with a nearly innumerable multitude of closely set spines which are longest not far from the terminal spine and from hère decrease slightly in length behind and considerably towards the bottom of the incision. In the small spécimen the telson (fig. 3 k) has its distal fourth somewhat différent : the outer margins of this part converge conspicuously behind, and the incision is consequently less broad at its distal end. Length of a female with marsupium from the end of rostrum to the tip of telson 47 mm. Colour. — The large spécimens were « blanc translucide avec taches ruber pâle sur tout le corps ; yeux noirs ». The small spécimen, which measures 18 mm., was « transparent avec taches ruber ». Localities. — Lat. 7i°oo/ S., long. 8g°i5' W., May 11, 1898, dredge ; two large spéci- mens. — Lat. 7o°48' S., long. gi°54' W., April 27, 1898, swab; one small spécimen. Distribution. — Holt & Tattersall mention two spécimens from lat. 780 25' 45" S., long. i65° 3g' 6" E. — Coutière enumerates many stations from the area explored by the French Expédition. SCHIZOPODA AXP CUMACEA i5 Remarks. — A. maxitna is a little longer and more robust than A. Ohlinii, but the two species agrée closely with each other in most structural features. I hâve found two good différences between them. In A. maxiina the eye-stalks and eyes are considerably depressed, the eyes look essentially forwards, occupying not only the front end but the major part or nearly the whole outer margin of the stalk, so that the inner margin of the stalk itself is much or generally several times longer than the outer free margin behind the eye; finally, the front latéral margin of the carapace is in the main vertical, so that its lower prominent rounded angle lies scarcely behind the insertion of the eye-stalks. In A. Ohlinii the eye-stalks and e3res are feebly depressed; the eyes look essentially forwards, the free outer margin of the eye-stalk being about as long as the inner margin ; finally, the front latéral margin of the carapace is in the main extremely oblique, so that its lower prominent rounded angle lies much behind the insertion of the eye-stalks. III. - The Order CUMACEA Of this order three spécimens belonging to three différent species were captured. But one of the spécimens has the carapace very broken and besides it seems to be far from adult; for thèse reasons it became necessary to abandon every idea of giving a description of this form which cannot be referred to any antarctic species hitherto known. The two other spécimens are described hère as représentatives for two species new to science. i. — Cyclaspis glacialis n. sp. (PI. III, fiSs. i a—ig The spécimen is a well developed female, but having no marsupium it is not adult ; it measures io.3 mm. in length. It shows some resemblance to C. aicstralis G. O. S., but differs especially in lacking the latéral carina on the carapace and the sub-dorsal pair of carinae on the three posterior cephalothoracic and the two anterior abdominal segments. Carapace slightly more than one-third of the total length, somewhat compressed ; its vertical height is a little more than three-fourths of the length. It is dorsally keeled ; in the anterior three-fifths this keel is broad and in the main rounded, but besides it has a secondary extremelv narrow, low but distinct carina in the middle Une (fig. i b) ; in the posterior three- fifths of the carapace the main keel is slightly developed and without secondary carina. Each half of the dorsal surface of the anterior three-fifths of the carapace is somewhat excavated, and an oblong moderately arched area occupies the submedian part of each excavation ; it is the existence of this pair of excavations which produces the aspect that the anterior part of the carapace is broadly keeled. The ocular lobe is moderately broad and scarcely prominent above ; eye-facets can not be perceived. The pseudorostral lobes touch one another just in front of the eye-lobe which reaches nearly to the front end. The antennal notch is shallow, moderately open; the tooth nearly acute. First leg-bearing segment entirely concealed; second dorsally shaped as the posterior part of the carapace ; third and fourth segments without any keel ; fifth segment with a narrow, well developed carina. 16 EXPEDITION ANTARCTIQUE BELGE Abdomen slightly longer than the cephalothoracic région ; the five anterior segments subcylindrical with a médian, well defined, narrow, rounded carina ; on the sixth segment this carina is manifest in front, but slightly developed behind the middle (fig. if). Third maxillipeds (figs. i c — i d) hâve the distal part of the second joint a little narrower than its proximal portion, because the joint increases only a little in breadth from the middle to the base of the third joint ; fourth joint is only twice as broad as the third and twice as broad as long ; fifth joint is serrated along the inner part of the front margin and the distal part of the inner margin ; sixth and seventh joints equal in length. First pair of legs (fig. i é) extend only a little beyond the pseudo-rostrum (fig. la). Second joint is somewhat longer than the sum of the five distal joints ; it begins to taper in breadth at the base of the distal third of its total length. Fifth joint is much longer than the sum of the third and the fourth, it is exactly as long as the sixth, and nearly twice as long as the seventh. The peduncle of the uropods (fig. i/) is scarcely longer than two-thirds of the sixth abdominal segment and just as long as the exopod. The endopod (fig. i g) tapers in an acute point and has along the middle of its inner margin about eight serrations, probably insertions for spines broken off with the exception of the last one. The colour was noted to be : « Flavus avec taches arrondies blanches. » Locality. — Lat. yi° 14' S., long. 8o° 14' AV., May 12, 1898, swab ; one spécimen. 2. — Campylaspis frigida n. sp. 'PI. III, figS. 2 (7— j n The spécimen is an adult female with the marsupium filled with brood ; it measures 6 mm. In gênerai aspect it is similar to C. verrucosa G. O. S., but it differs in several particulars and especially in the shape of fourth joint in third maxillipeds. The carapace has the integuments so thin that it became impossible to give really good figures of the knots : when the animal is immersed the outlines of the nodiform protubérances are partly not discernible, and when it is taken out of the liquid it almost instantly collapses. The figures given convey the impression that the majority of the knots are arranged in rows and that they differ much from each other in size. In other respects the céphalothorax differs scarcely from Sars' drawings of C. verrucosa. The antennulae (figs. 2 c — 2 d) are of moderate length ; the basai joint is strongly curved, evidently shorter than the sum of the two others ; the second joint is somewhat longer than the third. The outer flagellum is a little shorter than the sum of the two distal joints of the peduncle; it is divided into four joints, the first very short, the third very long and longer than the sum of the first and the second, with a very long sensory seta at the end ; the fourth joint is twice as long as the first, with a couple of sensory setse. The inner flagellum is a small oblong joint. First maxillipeds (figs. 2e — 2/) almost as in C. verrucosa. Second maxillipeds (figs. 2g — 2/1) differ from those in C. verrucosa especially in the shape of the penultimate joint, but this joint is similar to that in C. horrida G. O. S. Third maxillipeds (fig. 2 i) hâve the fourth joint shaped quite différent from that met with in C. verrucosa and allied forms. In C. verrucosa the fourth joint is oblong, about twice SCHIZOPODA AND CUMACKA 17 as long as broad, and the fifth joint is inserted about at the middle of its distal margin, but in C. frigida the fourth joint is triangular and so strongly expanded on the inner side that it is as broad as long, furthermore the major part of the very long distal margin is considerably concave and free, while the following joint is inserted on the most outer part of this margin. (It may be added that this fourth joint is completely alike in both maxillipeds ofthird pair.) The other joints of thèse appendages differ slightly from those in C. verrucosa. First thoracic legs (fig. 2 k) nearly as in C. verrucosa, but in the latter the fourth joint is somewhat longer than the fifth, while in C. frigida the différence between the length of thèse joints is slight. — Second thoracic legs (fig. 2 /) nearly as in C. verrucosa, but the fifth joint is somewhat shorter than the seventh, while in the last-named species both joints are equally long. Fifth abdominal segment (fig. 2111) has a very conspicuous transverse impression somewhat behind the middle. The uropods (figs. 2 m — 2 n) hâve the peduncle twice as long as the endopod; both rami are proportionately a little shorter than in C. verrucosa, while in other respects there is scarcely any différence between the uropods of the two species. The colour was noted to be : « Céphalothorax isabellinus, abdomen incolore ». Locality. — Lat. 70048' S., long. 910 54' W., svvab, April 27, 1898; one spécimen. Remarks. — One might think that C. frigida is identical with C . verrucosa var. antarctica described and figured by W. T. Calman in his report on the Cumacea from the National Antarctic Expédition. But in 1907 I laid my figures given hère before that author who made a new préparation of the third maxillipeds of his species, and the fourth joint of thèse appendages presented the normal shape, thus differing widely from my species. m R 57 EXPLANATIOX OF THE PLATES ig- 2 a. » 2b. » 2 C. » 2 d. » 2 C . » 2/. » 2 g- PLATE I Fig. i. — Euphausia longirostris n. sp. Fig. i a. — Céphalothorax with eye and proximal part of antennula and antenna, from the left ; X ii/2. » i b. — Left antennula of the same spécimen, from the outer side ; X 17/2. » if. — Major part of the peduncle of right antennula, from above ; X il. Fig. 2. — Thysano'êssa macrura G. O. S. • Front part of céphalothorax with appendages of a voung spécimen, measuring 8 mm., from the left ; X 21. ■ Same, from above ; X 21. • Left maxilliped of the same spécimen ; X 3o. Left first thoracic leg of the same spécimen ; X 3o. Posterior part of abdomen of the same spécimen ; X 12. Distal part of telson of the same spécimen ; X 5o. • Front part of céphalothorax with appendages of a spécimen in the last larval stage, measuring 5.7 mm., from the left ; X 21. » 2 h. — Distal part of telson of the spécimen shown in fig. 2 g, from above ; X 5o. — To the right of the figure is shown separately the hook from the base of the inner margin of the broad movable spine. Fig. 3. — Last laix 2 C. » %à » 2.e. )> 2/ » zg- n 1 h. » 2 i. )) 2 k. » 2/. » 2m, ■» 2 11, EXPEDITION ANTARCTIQUE BELGI SCHIZOPODA AND CUMACEA. il. 2S H.J. Hansezi âsl. I N Uoller se Fig. i. Euphausia longirostris n. sp. Fig. 2. Thysanoëssa macrura G. O.S. Fig. 3. Euphausia crystallorophias Holf et Tatt Fig 4 Euphausia superba Dana. EXPEDITION ANTARCTIQUE BELGE. \^JJ SCHIZOPODA AND CUMACEA. Pi. Il T.N.Moiler se Fig i Fuphausia sp. Fig 2 Pseudomma Belgicae (HJ.H.) Fig. 3. Antarctomysis raaxima (HJ.H) EXPEDITION ANTARCTIQUE BELGE. /,/ z i i ., 2 / 2 h 2 h SCHIZOPQDA AND CUMÀ.CEA Ijl Il J H.Ul.S.-Ij J^l 2 ,? 2 k /.• Fig. i Cyclaspis glacialid n.sp. Fig. _>. C ampj'iaspis frigida n.sp. TX.Mcli.-r se LISTE DES RAPPORTS SCIENTIFIQUES PUBLIÉS SOUS LA DIRECTION DE LA COMMISSION DE LA "BELGICA,, Les mémoires dont les titres sont précédés d'un astérisque (♦) ont déjà paru. Le classement des rapports dans les volumes III, IV, VI, VII, VIII et IX sera fait ultérieurement. VOLUME I. RELATION DU VOYAGE ET RÉSUMÉ DES RÉSULTATS, par A. de Gerlache de Gomery. ♦TRAVAUX HYDROGRAPHIQUES et INSTRUCTIONS NAUTIQUES (Premier fascicule), p' G. Lecointe. Frs 67.5 VOLUME II. ASTRONOMIE ET PHYSIQUE DU GLOBE. ♦ETUDE DES CHRONOMETRES (deux parties), par G. 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