54

UNIVERSITY OF CALIFORNIA
AT LOS ANGELES

The RALPH D. REED LIBRARY

DEPARTMENT OF GEOLOGY

UNIVERSITY OF CALIFORNIA

LOS ANGELES, CALIF.

MEMOIRS

GEOLOGICAL SURVEY

THE UNITED KINGDOM.

figures atifo Desrrtjrttnns

ILLUSTRATIVE OF

BRITISH ORGANIC REMAINS.

DECADE- II.

PUBLISHED BY OUDER OF THE LORDS COMMISSIONERS OF HER MAJESTY'S TREASURY.

LONDON:

PRINTED FOR HER MAJESTY'S STATIONERY OFFICE :

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LONGMAN, BROWN, GREEN, AND LONGMANS.

1849.

MEMOIRS

GEOLOGICAL SURVEY

THE UNITED KINGDOM.

itesrrqrtinns

ILLUSTRATIVE OF

BRITISH ORGANIC REMAINS.

DECADE II.

PUBLISHED BY ORDEE OF THE LORDS COMMISSIONERS OF HER MAJESTY'S TREASURY.

LONDON:
PRINTED FOR HER MAJESTY'S STATIONERY OFFICE:

PUBLISHED BY

LONGMAN, BROWN, GREEN, AND LONGMANS.

1849.

LONDON: TKISTED BT TV. CLOWES AND sous, STAMFORD STKEKT.

75-

a "7

NOTICE.

PALJSONTOLOGICAL researches forming so essential a part of geological
investigations, such as those now in progress by the Geological Survey
of the United Kingdom, the accompanying plates and descriptions of
British Fossils have been prepared as part of the Geological Memoirs.
They constitute a needful portion of the publications of the Geological
Survey, and are taken from specimens in the public collections, or lent
to the Survey by those anxious to advance this branch of the public
service. Although numerous drawings had previously been made, and
engravings from them considerably advanced, it was not thought expe-
dient to commence their publication until the large collections of the
Survey could be well examined, which a want of the needful space
has, until the present time, considerably retarded. This impediment
to progress is now being removed, and when the collections can be
properly displayed in the New Museum of Practical Geology, in
Jermyn Street, it is hoped that the public will have an opportunity
of gradually obtaining, in a convenient manner and at small cost, a
work illustrating some of the more important forms of animal and
egetable life there prese rved, and which have been entombed during
the lapse of geological time in the area occupied by the British islands.

The plan proposed to be followed in the work, of which the two
Decades now published form a part, is as follows : —

To figure in elaborate detail, as completely as possible, a selection of
fossils, illustrative of the genera and more remarkable species of all

IV NOTICE.

classes of animals and plants the remains of which are contained in
British rocks ; to select especially such as require an amount of illus-
tration which, to be carried out by private enterprise, would require
a large outlay of money, with little prospect of a return, and a long
time to accomplish, but which, by means of the staff and appliances
necessarily employed on the Geological Survey, can be effected at small
cost, and with a rapidity demanded by the publication of the Maps and
Memoirs of the Survey ; thus, it is hoped, affording an aid to those
engaged in the sciences with which this work is connected, that they
might not otherwise have possessed, and which may materially promote
the progress of individual research.

H. T. DE LA BECHE,

Director- General.

Geological Survey Office,
18th July, 1849.

BRITISH FOSSILS.

DECADE THE SECOND

THE second Decade of representations of British Fossils contains illus-
trations of the genera and species of Trilobites.

These remarkable animals, belonging to a group of Crustacea, of
which we find no traces in strata formed subsequently to the Palaeozoic
period, were first observed in British rocks, Nevertheless, the investi-
gation of those species found in our country is as yet far from complete.
Our recorded knowledge of them is chiefly contained in the works of
Sir Roderick Murchison and of Lieut. -Colonel Portlock. In the
" Silurian System," only are figures to be found of our commoner spe-
cies, and in the " Report on the Geology of Londonderry, Tyrone, and
Fermanagh," is the only systematic dissertation on their arrangement,
which has yet been published in Britain.

During the progress of the Geological Survey through the Silurian
districts of Wales and the bordering counties, much new and import-
ant material has been collected towards the elucidation of the structure,
affinities, and distribution of Trilobites. The following figures and de-
scriptions consequently contain much that has not been before noticed
respecting these animals, and new light will be found thrown on several
features of their organization.

The Trilobites selected as subjects for this Decade are species of the
genera Phacops, Hlcenus, Asaphus, Ogygia, Calymene, and Ampyx.
Some of them are renowned and characteristic forms, such as Phacops
(Dalmannia) caudatus, Illcenus (Bumastus) Barriensis, Asaphus ty-
rannus, and Oyyyia Buchii, which, whilst they furnish excellent typical
figures illustrating generic or sub-generic groups, acquire an additional
[ii.] b

yi BRITISH FOSSILS.

value on account of the abundant details of structure, which, through
our extensive collections, we are enabled to delineate ; others, as
Ogygia Portlockii, Calymene tuberculosa, and Ampyx nudus, are critical
species, the history of which has been hitherto imperfectly known ; and
a third class consists of entirely new forms, such as Illcenus Davisii
and Olenus micrurus ; the last mentioned trilobite has great interest,
having been found in the most ancient fossiliferous strata of the Silurian
System, whilst at the same time it constitutes a good representative of
the numerous forms of the genus Olenus, which occur in the oldest
rocks of the Continent.

The descriptions of all the species, with the exception of Ampyx nudus,
have been drawn up by Mr. Salter, whose attention has for some time
been specially directed to Trilobites.

Illustrations of the other British genera of Trilobites are in pre-
paration.

EDWARD FORBES.

July, 1849.

BRITISH FOSSILS.

DECADE II. PLATE I.

PHACOPS CAUDATUS.

[Genus PHACOPS. EMMERICH. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitae.) Eyes largely facetted ; facial suture ending on the
outer margin ; thorax 1 1 jointed.]

[Sub-genus Dalmannia. Depressed ; pleurae pointed and bent back at a distant fulcrum ;
glabella not inflated, with three lateral lobes; facial suture within the edge in front; head
angles long-spined ; hypostome obtusely pointed ; tail with a many-jointed axis, and
•without lateral spines.]

DIAGNOSIS. P. (Dalmannia) fronte angulato ; oculis maximis pyra-
midatis, e sulco glabellari basali ad tertium et supra extensis ; pleuris
recurvis, fulcro ad dimidium ; caudce apice mucronato, axi 11-12 annulate,
costis lateralibus 7, rarius 6, arcuatis, duplicatis, ad marginem Icevem
abrupte terminatis.

SYNONYMS. — VAR. a. Vulgaris. — Fronte capitis angulato ; apice caudte
brevimucronato. — Plate I., figs. 1 to 12, and fig. 15.

Trilobus caudatus, BRUNNICH (1781), Kjobenh. Sellsk. Skrifter. Nye
Samml., vol. i., p. 392. Asaphus caud., BRONGNIART (1822), Crust. Foss.,
t. 2, f. 4 (not 3, f. 9). Trilob. caud., SCHLOTHEIM (1823), Nachtrage,
35. 11. Asaphus caud., DALMAN (1826), Palead., t. 2, f. 4. GREEN
(1832), Monogr. Trilob. N. Amer., cast 17. BUCKLAND (1836), Bridgw.
Treat., pi. XLV., f.9-11. MURCHISON (1837), Sil. Syst., pi. 7, fig. 8 a.
A. tuber culato-caudatus, ib., fig. 8b. A. caud. and A. tuber culato-caud.,
MILNE EDWARDS (1840), Crust. 3, 308. P. caud., BURMEISTER, Org.
TriL, t. 4, f. 9. Ray edition (1846).

VAR. ft. Longicaudatus. — Plate I., figs. 13, 14. — Axi angustiori, fronte
capitis cauddque longimucronatis.

Trilobite with caudal process, PARKINSON (1811), Organic Kemains, vol.
iii., t. 17, f. 17. Asaphus longicaudatus, MURCHISON, Sil. Syst., pi. 14,
figs. 11 to 14. MILNE EDWARDS, Crust. 3, 308. Phacops mucronatus,
BURMEISTER, Org. Tril., 113 (exclude all synonyms except Murch.). Ray
edit., 95. \_Phac. longicaud., ROUALLT (1847), Bull. Soc. Geol. Fr., 2nd
Ser., 4, 320?].

Description of Var. «. — Four or five inches long; ovate; length as
to width varying from 10 • 6 to 85 ' 6 ; thorax longer than either head or
tail ; the latter about equal to the head, excluding the produced mucro ;

[n. i.] 2 B

2 BRITISH FOSSILS.

axis of the whole body considerably narrower than the sides. Head
finely granular all over, semicircular, without the slightly produced
snout, or the long, stout, posterior horns, which are broad at the base,
and reach the seventh or eighth thoracic ring. Glabella coarsely
tubercular, widened above, more than one-third the width of head, the
forehead lobe a transverse rhomb, separated by deep, broad, oblique
furrows which nearly meet, from the upper side lobes ; three lateral
lobes and neck lobe all nearly equal in width, and together equalling
the forehead lobe, the first and second lie straight across, and leave but
a narrow ridge down the middle : strong axal furrows separate the
glabella from the triangular cheeks, of the surface of which the large
pyramidal eyes occupy a variable proportion ; a lunate depression
surrounds their outer edge, and this is sometimes extended over more
than half the width of the cheek, sometimes barely half, giving a con-
siderable difference in appearance. The length of the eye, which is
sharply curved, is uniformly from the first basal furrow to the middle of
the upper one ; eyelid with a deep concentric groove ; lentiferous sur-
face considerably broader forwards, lenses about 240*, 8 or 10 in a
vertical row. In the cast, which represents the crystalline layer behind
the lenses, the surface is covered with close-set, circular pits, with
narrow distinct borders (Fig. 5) ; in these hollows the moderately convex
lenses are set, and in most specimens we see no cornea over them.
In two perfectly preserved eyes from Ledbury (Fig. 4), the cornea is,
however, present, and contrary to Professor Burmeister's prediction, is
distinctly convex over each lens, the intermediate portions being orna-
mented with tubercles and granules, so as to leave no doubt of its
being the true exterior ; it is, too, continuous with the other portions of
the preserved shell. The cornea does not rise, as in some other species,
into elevated ridges between the lenses, but is flat, or in other specimens
(Fig. 6), it sinks down between them. In Fig. 4 a lens or two is seen
to be undeveloped and very small, among other perfect ones. The
facial suture exactly circumscribes the glabella in front, falls perpen-
dicularly to the eye, and arches outwards and upwards from its lower
angle to the outer margin of the head, on the lower face of which it
extends along the margin further back than on the upper surface (see
Fig. 10 a). The cheek-pieces are united in one (as in all the genus)
across the front, and there is no extra piece inserted between them above
the hypostome. The latter (Fig. 3) is parabolic, obtusely pointed, the
sides a little waved, and the base of attachment extended ; a transverse
furrow, within the tip, is connected with a marginal longitudinal one on
each side, a pair of lateral strong indentations indicate a second furrow

* Bucklaud, Bridgw. Treat., p. 399, reckons 400. This was probably intended for both
eyes.

BRITISH FOSSILS. O

above. Round the head a strong furrow separates the broad margin,
stops at the base of the spines, and there nearly meets the equally
strong neck furrow, which is arched down at its end. The margin in
front more or less produced into an obtuse point. Thorax with the
central lobe not separated by any strong furrow from the pleurae, which,
in English specimens, are half as wide again as the axis ; the axis is
a little fusiform, not broader than the base of the glabella, and either
has the rings smooth, tubercled at their outer edges, or with two tuber-
cles on the central prominent part : — all these variations occur on the
same thorax. The front pleurae are flat for the first half, then gently
curved down, and a little back, at the obscure fulcrum ; they are divided
by a moderately strong curved furrow for most of the length, and their
edge sharpened anteriorly (the flat surface not crossing the furrow as in
true Phacops) for bending. The extremities are truncate, and pointed at
the hinder corner ; posterior pleurae with the fulcrum at less than half,
much more curved back, and strongly pointed, overlapping the upper
corners of the tail. Whole surface of thorax finely granular. Tail
with the sides meeting below at nearly a right angle, and produced
more or less to a sharp point beyond this ; axis not much raised, and
gently tapering, ending a little abruptly at some distance from the
point ; it has 11 or 12 ribs, which are accidentally tubercular, like the
thorax, sometimes much so ; the sides have six, seven, or sometimes
eight narrow ribs, strongly arched down at their ends, where they abut
suddenly on the smooth margin ; each rib is sharply defined behind, and
duplicated on its forward edge by a fine rib, running parallel to it
along its whole length. The number of the ribs on the tail appears to
be as great in the young animal, judging from the beautiful specimen,
Fig. 7, from Mr. J. Gray's collection.

Variations. — The tail margin varies much in width. In fig. 15 it is
very narrow, and the apex little produced. Most of the specimens of
var. a, in shale or mud (Fig. 11), have the axis of the head and tail
narrower than those in limestone (Fig. 12), and the tail itself broader
and more mucronate. From Ludlow we have specimens of this form,
with all degrees of attenuation in the mucro. The larger head of
var. /3 (Fig. 14), has the outer margin more expanded than in any lime-
stone one yet seen.

Sex. — Some differences are very observable between individuals of
this species, as well as of other species and genera, which are possibly
referable to sex. We find the male in insects distinguished by large and
prominent eyes, extra length of spines, and narrowness or depression of
the body ; the latter character is sexual in the Crustacea. It is natural
to look for some sexual distinctions in animals with such marked
forms as trilobites have, but an examination of Scrolls, the external

4 BRITISH FOSSILS.

characters of which, at least, imitate best those of trilobites, does not
help out the case. The differences pointed out there by Milne Edwards
and Audouin reside in the feet and appendages, not in any general
shape, prominence of eyes, or sculpture, and we can, therefore, only
surmise from general analogy, that certain individuals with the glabella
flattened so as to leave the eyes projecting, the body more depressed,
and the spines of the front and sides of the head, or the mucro of the
tail more developed, may be males ; while greater general convexity,
more convex glabella rising nearly as high as the eyes, and a tail not
attenuated into the mucro, but simply pointed, may mark the other sex.
Fig. 1 we think a female, and in this the eyes seen in front view (Fig. 1 a)
do not rise much above the glabella, and the body is convex, the tail
simply pointed ; but in others the glabella is depressed, especially be-
hind, and the front produced. In Fig. 9, supposed to be a male, the pro-
duced angular front is shown. Fig. 8 shows the great length the spines
of the head sometimes assume.

If P. longicaudatus, our var. /3, be identical with this species, and it
differs in nothing except the greater development of the processes, the
probability of this difference being sexual is confirmed, for there occur
in the same slabs individuals exactly alike, some with long spines to
head and tail, and others without them.

Affinities. — But one European species is sufficiently like ours to
render a close comparison necessary. We refer to the Asaphus mucro-
natus (Brongn.), which Professor Burmeister identifies with our var. /3 ;
however, he had not seen specimens, and we have them before us. The
head of that is regularly convex, the axal and glabellar furrows not
deep, the eyes placed further forwards, the margin narrow. The tail
is like, but the ribs do not imbricate posteriorly, and the intermediate
furrow divides them more equally. The mucro, too, is recurved, as in
P. proevus, with which, without being identical, it is closely allied.
Asaph. pleuroptyx (Green, cast 18), has 11 or 12 lateral ribs to the tail,
extending below the very narrow axis ; but with P. limulurus (Green,
cast 16), from the Niagara shale, there are so many points of resem-
blance, that we can hardly persuade ourselves they are distinct. Speci-
mens in the cabinets of Sir C. Lyell and Dr. Bigsby show that the form
is more elongate, the pleurae shorter, the glabella contracted at the base,
and the eyes perhaps smaller ; the tail narrow, its lateral ribs faint and
but little arched, while the extremity of the axis is more prominent.
The head wants the strong marginal furrow, and the posterior spines
extend but a little way down (to the fifth rib, Hall). While avoiding
the risk of a doubtful synonym, we cannot value these mere proportional
characters as specific, and believe that a larger series will unite the
above and P. Wetherilli (Green, cast 20), to the English species.

BRITISH FOSSILS. 0

History. — When Brongniart made the first scientific attempt to
classify trilobites, his genus Asaphus confessedly stood as debateable
land between Cafymene and Ogygia, but he clearly pointed out that
the type of the genus, when restricted, should be Asaphus corniyerus,
a species^ossessing smooth eyes and eight joints to the thorax. The
characters " Tubercules oculiformes reticules " were drawn from the
present species, and the figures also from Dudley specimens. Dalman
followed, without much improving this classification, but Quenstedt, in
1837, clearly separated the group of trilobites with facetted eyes,
(meaning thereby with large prominent facets), and Emmerich named it
Phacops. In the treatise on the 'c Morphology, Classification, &c., of
Trilobites," published 1845, in Leonhard and Bronn's " Neues Jahr-
buch," Emmerich pointed out the subdivision Dalmannia, making Ph.
caudatus (Briinn.), its type. Burmeister, however, has thought fit to
retain all under Phacops, and the characters of one group pass so gra-
dually into those of another, that we prefer following his plan, though in
the Memoirs of the Geol. Survey, just published, we have adopted the
genus (vol. ii., part 1, page 337.) Sir R. I. Murchison, in 1837, gave
figures of the ordinary and the tuberculated forms, and there was quite
sufficient to justify him in making the var. longicaudatus a species.
After observation of many intermediate forms, however, we unite them
without much doubt of the propriety of so doing. Green, in 1832, did
some service by publishing his casts, and he would have done better had
he not permitted them to be carved to make them more plain. Milne
Edwards adopted the previously published species in his excellent work
on recent Crustacea. Professor Burmeister confused the synonyms of
this species, by too hastily uniting P. mucronatus with our var. /3 ; Dal-
man had well separated the two in 1826. In uniting, as we have done,
the var. /3 to the typical form, we believe we shall be justified by most
naturalists, when the numerous varieties common in every collection are
examined with a view to this. The combination of characters is the
same in both, and variation in isolated points should always be sus-
pected. The reference of such differences to sex is merely speculative,
and will require much observation to confirm.

British Localities and Geological Range. — Distributed throughout
the Silurian districts, from the lower LLANDEILO FLAGS TO UPPER
LUDLOW ROCK. The shales of Kirkcudbright, Scotland (J. W. S.) ;
rarely in the Coniston limestone, Westmoreland ; quoted also by Prof.
Sedgwick, from Coldwell, ditto (Geological Journal) ; this is a mistake, as
is also the quotation in the list of fossils, ib., vol. i., p. 20. Upper Silurians
of Denbighshire (J.W. S.). Near St. Clairs and Narberth, in Llandeilo
flags. Marloes Bay, Pembrokeshire (Phillips). Dynevor Park, and nu-
merous localities south and west of Llandeilo ; also Rhiw-rhwych and

G BRITISH FOSSILS.

Cefii Llwydlo, north of Llandovery (J. W. S.) Everywhere in upper
Silurian rocks, Herefordshire and Shropshire (Murchison, " Sil. Syst.")
Especially abundant in Dudley limestone and shales. Usk, Monmouth-
shire ; in Ludlow and Wenlock rocks (J.W. S.) Horse-shoe Farm, Tort-
worth ; Huntly-hill, Gloucestershire ; Caradoc sandstone ; Woolhope
limestone and upper Silurians of Woolhope, Abberley, and Malvern
districts. (Geol. Surv.) Not yet found in Ireland.

Var. /3. — Marloes Bay, and St. Ishmael's, Pembrokeshire (Phillips).
Cwmdwr, Brecknockshire ( J. W. S.). Brindgwood Chase, in Ludlow rocks ;
Burrington, in Wenlock shale ; near Ludlow, Aymestry, and Nash Scar, Here-
fordshire (" Sil. Syst.") Usk, Monmouthshire, from Wenlock shale to
upper Ludlow rock ; Abberley and Malvern (Phillips).

Foreign Distribution. — In Gottland, upper Silurian, rare (Dalman
and Hisinger.) Ripley, Ohio (Green ; — the localities quoted from
Canada are erroneous, Dr. Bigsby's specimens being of quite different
species, but one, which is probably the true species, was found by him
at Gaspe, Gulf of St. Lawrence).

EXPLANATION OF PLATE I.

Fig. 1. Perfect specimen, in Mr. Tennant's cabinet, probably from Dudley.

Fig. 1 a. Front view of head ; 1 b, side view.

Fig. 2. Same, dissected ; a, front lobe or forehead ; b, spira or neck lobe ; c, cheek or
•wing ; d, margin ; e, axis of body ring ; /, fulcrum of ditto ; g, part of the axis of a tuber-
culated specimen ; k, intermediate ribs of the tail. (These are the indications of separa-
tion between the segments.) The g at the tail margin should be omitted.

Fig. 3. Hypostome from Ledbury.

Fig. 4. Magnified view of surface of eye, the cornea tuberculate between the convex
portions which cover the lenses. At (a a), some small abortive lenses are seen. Ledbury.

Fig. 5. A cast of the interior of the eye, the cornea having been removed, and the
lenses fallen out. Vinnal Hill, Ludlow.

Fig. 6. An eye, with very prominent lenses, which are partly visible, where the cornea
has been broken away. Ledbury.

Fig. 7. A fine young specimen, with rather prolonged tail. Dudley, Cabinet of Mr.
John Gray.

Fig. 8. Specimen, with vastly prolonged head spines. Dudley Museum.

Fig. 9. Head, with produced front (male ?) Bodenham, Woolhope.

Fig. 10. Cheeks united across the front, and separated from the rest of the head along
the facial suture. The course of the suture beneath (at a) is rather different from that of
the upper side. Vinnal Hill, Ludlow, a rich locality.

Fig. 11. Tail, with the axis narrow and the point prolonged. Intermediate between
P. caudatus and the var. lo?igicaiidatus. Vinnal Hill.

Fig. 12. Tail of ordinary form. From Wenlock limestone of Clincher's Hill, South
Malvern.

Fig. 13. Tail of var. /3, longicaudatus. Craig-y-Garcyd, Usk, in Wenlock shale.

Fig. 14. Head of same variety. Burrington, Ludlow.

Fig. 15. Tuberculated (diseased?) tail, with very narrow border. Rock Farm, May
Hill.

Fig. 10. Accidentally introduced; it belongs to the species next described. Long's
Quarry, Tortworth.

BRITISH FOSSILS.

Other British Species of Phacops, of the Section Dalmannia.

1. P. sp. [fig. 16 in PL I.]

P. Icevis, capite quam in P. cauduto, nisi lobis glabellce tumidioribus ; — caudd triangulari,
fere aquilatera, convexa, apice acuto hand mucronato, axi 13-16 annulato, costis lateralibus
10-12, simplicibus, vix curvatis, ad marginem cequalem angustum abrupte terminatis.

Length of tail l£ inches. There are but imperfect heads in the collections of the Geo-
logical Society and Geological Survey. The characters of the tail distinguish it from
P. caudatus; it has much more numerous ribs, which are but little curved, and not dupli-
cate ; the margin, too, is equal all round, not expanded or mucronate at the end. Young
specimens have not the full number of ribs, and a few of the upper ones are slightly
divided. The most prominent analogy is with P. Hausmanni, Brongn. ; but that is
strongly tuberculate, almost spinous, all over. P. pleuroptyx (Green), is also like, but has
the lateral ribs duplicate. The species of this group so closely resemble each other, that
we dare not give a name. Should it prove new, it might be called P. Weaveri.

Localities. — Caradoc sandstone of Long's Quarry, Damory Bridge, and Charfield
Green, Tortworth, Gloucestershire ; (all small) ; Woodford Green, ditto ; (large).

2. P. obtusicaudatus.

P. capite quam in P, caudato, sed latiore ; — caudd brevi, lato, subtriangulari, apice
angulato, obtuso ; axi lato, convexo, 11-12 annulato, obtuso ; costis lateralibus 9, duplicatis,
rectis, ad marginem angustum aqualem abrupte terminatis,

We merely note this curious species here ; it will be figured and described in Prof.
Sedgwick's work on Westmoreland.

Locality. — Coldwell, in flags above the Coniston limestone, Westmoreland.

3. P. truncato-caudatus, Portlock, Geol, Rep. Tyrone, &c., pi. 2, f. 1-4, and Para-
doxidesl Bucepliali var., pi. 1, f. 8 (hypostome).

P. granulatus, capite antics truncato, oculis maximis subdepressis ; pleuris obtusis, fulcra
ab axi valde remoto ; caudce axi IS-annulato, angusto, costis lateralibus 14-16, apice
emarginato.

This interesting species, while in the large eyes and strong head spines, numerous joints
of the tail, and general depressed form, it is nearly allied to the other Dalmannice, — yet
indicates moae than any other the close affinity of this section with Phacops, for the facial
suture is only just within the margin, the tail rather rounded than produced, the pleurae
have their furrows strong and curved forwards at their obtuse ends, and they are bent
down at the distant fulcrum, so as to be much better fitted for rolling up than is usual iu
Dalmannia. For the first half of the thorax they are scarcely at all bent back from the
fulcrum ; the posterior pleurae are more in the usual way. The hypostome is very much
extended at its base, is pointed, and has two pair of oblique furrows.

Localities. — Lower Silurian. Tyrone, Ireland. Coniston, Westmoreland. Horderly,
Shropshire.

VAR. ft affinis. Caudce axi latiore — Dalmannia affinis, Salter, in Memoirs of the Geol.
Survey, vol. ii., part 1, pi. 5, f. 5.

It is to be feared there are not sufficient grounds for separating this species, founded only
on caudal shields. A tolerably perfect tail in Mr. D. Sharpe's collection, and an imperfect
one in the Survey Collection, have the axis considerably wider than in Portlock's
originals. Specimens, however, in Sir R. I. Murchison's cabinet, show intermediate
characters.

Localities.— Lower Silurian. Llandowror, Caermarthenshire. Coniston, Westmore-
land.

Phacops is a widely distributed genus or group of trilobites, remarkable for the large
facets of the eyes, —the distinct trilobation of head, thorax, and tail, the furrows separating

8 BRITISH FOSSILS.

the lobes being strong and deep, — and for possessing eleven joints in the thorax, a number
apparently never deviated from. Besides these, in a large part of the genus the convex
form of head and tail, the curvature of the segments of the thorax, and the sharpening of
their anterior margins, eminently fit the animal for rolling up into a compact ball ; for this
purpose it is as completely constructed as Calymene, while it has the advantage over the
latter genus in its large organs of sight. It may be considered as the very type of a Tri-
lobite, possessing all the characteristics of the tribe, with a compact and elegant form. And
while the whole group is so bound together by common characters as to render it difficult
to separate it into distinct genera, there is a great variation of form among the numerous
species. Quenstedt, and after him Emmerich, united them all, and Professor Burmeister
has not ventured to dismember the genus. Subgenera, however, have been frequently
pointed out, and the groups so formed are very natural. We have —

1st Convex species, with the pleurae rounded at the end, and sharpened for rolling ; the
glabella inflated, and with but one lobe at the base ; the facial suture beneath the margin
of the head in front ; the head angles rounded, the tail of few joints. — Portlockia, McCoy.

2nd. Moderately convex, with the pleurae rounded ; the glabella not inflated, but with
(3) distinct lateral lobes ; facial suture marginal in front ; head angles rounded, or
variously produced, tail few (less than 11) jointed, rounded or pointed. — PJiacops,
Emmerich.

3rd. Characters as given above. — Dalmannia, Emmerich.

4th. Flattened ; pleurae pointed, or even mucronate ; glabella and facial suture as in
Dalmannia ; head angles long-spinous ; tail many-jointed, the margin produced into spines.
— Cryphceus, Green; Pleuracanthus, Milne Ed w.

Odontochile, Corda, is synonymous with Dalmannia, and his Asteropyge and Metacan-
thus apparently with Cryphaus.

The genus is found in all Silurian strata, and existed till the commencement of the
Carboniferous system. The distribution of the various subgenera in Britain is as follows : —

Portlockia is found in all the above strata. P. Sloltesii, Milne Edw., and P. sublavis,
McCoy, Silurian. P. Latreillii, Steininger, P. yranulata and P. Itevis, Munster, Devonian
and lower carboniferous rocks, Devonshire and Cornwall.

Phacops is Silurian. P. Odini, Eichwald, P. Brongniartii, P. Dalmannii, P. Jamesii,
Portlock, Lower Silurian. P. Downingia, Murchison, Upper and Lower Silurian.

Dalmannia, Upper and Lower Silurian.

Cryphtsus, Green [ C. callitelus, &c., so named before the definition of Milne Edwards'
genus, Pleuracanthus], Devonian. A specimen of C. arachnoides, Goldfuss, found at
Torquay, Devonshire, is in the collection of Mr. D. Sharpe.

J. W. SALTER.
June, 1849.

•

BRITISH FOSSILS.

DECADE II. PLATE II.

ILUENUS DAV1SII.

[Genus ILL^ENUS. DALMAN. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitse.) Head about a quarter of a sphere ; eyes smooth,
remote ; facial suture ending on the posterior margin behiiid the eye, marginal or sub-
marginal in front ; hypostome entire, separated from the facial suture by a transverse
rostral shield ; thorax segments 9 or 10.]

[Subgenus Illcenus. Axis of thorax separated from the pleurae by distinct furrows ;
fulcrum not close to the axis.]

DIAGNOSIS. /. capite pygidioque cequalibus ; oculis parvis prope sulcos
axales, a margins occipitali diametrum et plus distantibus ; thorace seg-
mentis 10, axi pleuris csquali ; fulcro in segmento primo ad axin approxi-
mate, in postremo dimidium pleura vix attingente.

SYNONYMS. /. Bowmanni [Specimens from Rhiwlas only], SAI/TEU
(1845), in Geol. Journ., vol. i., p. 20; also p. 8. Illcenus crassicaucta,
SHARPE (1848), Geol. Journ., vol. iv., p. 149.

Description. — Length 2^ to 3 inches. General form oval, very con-
vex ; length to width 17 : 10 ; the head and tail nearly equal in length ;
the thorax about two-thirds the length of either, and strongly trilobate ;
the axal furrows are carried less than half way up the head, and but a
very little way into the tail : head a quarter of a sphere, and regularly
convex, not peculiarly gibbous behind, where it is divided into three
nearly equal parts by the slightly converging axal furrows ; these curve
out again opposite the eye. The eye is of moderate size, gently lunate,
placed much nearer the furrow than the outer edge, and fully its own
length or more from the posterior margin. There is no internal ridge
at the place of the neck furrow. Facial suture divergent above the eye,
and slightly so below it, so as to cut the margin beneath the most pro-
minent curve of that organ. Rostral shield shuttle-shaped, covered by
transverse, close, sharp lines, the lower edge a little produced and over-
hanging. Hypostome ? Thorax of 10 narrow segments, the axis

strongly marked, convex, and subfusiform ; wider than the pleurae in
the forward segments, in the last only equal to them. The fulcrum is
very near the axis in the first segment, and in the last one is placed less
than half way along the pleura?, which are sharpened anteriorly beyond

[n. ii.] 2 c

2 BRITISH FOSSILS.

this point. The anterior segments are bent down slightly, and also a little
backward at the fulcrum, while the posterior ones are only bent down-
wards. Tail semicircular and moderately convex ; the axis indistinctly
marked out by two deep impressions, which sometimes form short rapidly-
converging furrows ; the upper corners are bent sharply down beyond the
fulcrum, in order to pass freely under the thorax-rings in rolling ; the
incurved under portion is concentrically striate as usual, not broad nor
indented by the termination of the abdominal axis.* General surface
of the head not well known ; a few wandering lines appear on one spe-
cimen near the margins of the cheeks ; the thorax rings are unorna-
mented : the general aspect is smooth.

Variations. — The axis in some specimens is narrower in proportion to
the pleurae (fig. 7).

Affinities. — This species requires close examination to distinguish it
from several others. /. Bowmamii has only nine rings to the very short
thorax. The ///. crassicauda has a head very gibbous behind, and
longer than the tail ; the eyes placed at less than their own length from
the neck margin, and remotely from the axal furrows ; the tail, which
has the axis distinctly marked all round, is scarcely longer than the
thorax, and the latter has its axis broader and flatter than in our spe-
cies ; the fulcrum of the pleurae not close in front, and at a full half
behind ; the incurved under portion of the tail is far broader and less
concave, and its lines of growth meet at an angle in the middle ; this
last portion is, however, not always visible for the purpose of com-
parison. The whole surface, too, is covered with strong, sharp lines,
which are certainly not conspicuous upon ///. Davisii, though the latter
is not quite smooth. ///. perovalis (Murch ) is a more elongate oblong
species ; the axis of the tail is very narrow, more so than in our nar-
rowest variety, extends one-third down its length, and is circumscribed ;
the incurved portion of the tail is broad. It is not at present justifiable
to connect even this latter with III. crassicauda, although it agrees more
nearly with it than with any other species.

History. — Apparently it was not known till Professor Sedgwick and
myself collected it at Bala, in what was then considered a peculiar band
of limestone, and it was too hastily identified with the 111 Boicmanni
(Mem. Geol. Surv., vol. ii., part 1, pi. 8, figs. 1, 2, 3), and as such pub-
lished in the list of Welsh fossils given in the 1st volume of the Geol.
Journ., p. 20 : the Rhiwlas locality belongs to the present species. Mr.
D. Sharpe, in noticing the probable occurrence of ///. crassicauda in
America, states that this fossil is found at Rhiwlas ; the present species
only is intended, and Mr. Sharpe differs with me as to its specific value.

* This indentation is frequently to he seen in Asaphus ; it is strong in IllcEnus
crassicauda, Dalm.

BRITISH FOSSILS. 3

British Localities and Geological Range — LLANDEILO FLAGS only. —
Abundant in the Bala limestone at Rhiwlas, at the foot of the lake, and
also at other localities in the immediate neighbourhood both north and
east of the lake (CoLL. OF GEOL. SURVEY). It appears, however, to
be but local, and its place is taken through many other parts of North
Wales, and all through South Wales, by the III. Boicmanni. It pro-
bably occurs in the lower Silurian limestone of Wrae, near Broughton,
Peebleshire ; some fragments were found there by Mr. James Nicol
(Geol. Journ., vol. iv., p. 206), which are with doubt referred to this
species, as also is another portion of thorax found in the limestone of the
Stincher river, Ayrshire, by Mr. Carrick Moore (?7>., vol. v., p. 13).

EXPLANATION OF PLATE II.

Fig. 1. Nearly perfect specimen. Rhiwlas, Bala ; in which locality all, except figs. G,
7, were found. Fig. 1 *, side view of ditto.

Figs. 2, 2*. Front and side views of a rolled-up specimen ; the want of gibbosity in the
head is shown in the side view.

Fig. 3. Dissected figure, a, central lobe ; b b, wings, upper side ; they extend further
inward on the under side ; c, axis of a middle thorax segment ; d d, fulcra ; e e, fulcra
of tail.

Fig. 4. A separate tail, showing the incurved under portion, d, where the upper crust is
broken off.

Fig. 5. Rostral shield, often found separate.

Figs. 6, 7. Tails of young specimens, showing the further extension of the furrows at
that age. Llechwedd ddu, Bala.

Fig. 8. Variety with narrow axis. The tail has been compressed from below, and
appears too small. Rhiwlas.

British species of Ulcenus proper.
* With 9 body-rings.

1. 7. Bowmanni, Salter, Mem. Geol. Survey (June, 1848), vol. ii., part 1, pi. 8, f. 1-3;
7. centrotus, Portlock (1843), Geol. Rep., pi. 10, f. 3-6, and probably f. 9.

7. capite magno, angulis posterioribus obtusis ; oculis remotis, admaryinem occipitalem
approximatis ; thorace caudd breviore.

Locality.— Llaudeilo flags, North and South Wales ; Kildare, Ireland.

** With 10 body rings.

2. 7. Davisii, as defined in our preceding description.

3. 7. Portlockii, Salter; 7. crassicauda, Portlock (1843), Geol. Rep. Tyrone, &c., pi. 10,
f. 7, 8 \_Thafeops ovatus, Conrad ; Hall, Paleont. New York (1848), pi. 67, f. 6 b. ?

7. capite magno, cattda parva, subtrigona ; oculis remotis [prominulis ?] ; thorace seg-
mentis 10, axi lato, pleuris abrupte deflexis et refexis ad fulcrum, quod ad dimidium pleura
uniusquisqiie positum est ; caudd depressa, subtriangulari, angulis extremis late truncatis.

That this neat species is not 7. crassicauda is very clear ; the shape of the tail, and the
abrupt backward bend of the pleurae, almost at right angles, distinguish it easily ; the
fulcrum is as far outward in the first segment as the last, an unusual character. We have
not seen specimens of 7. ovatus (Conrad); Hall's figure of that species (loc. cit., pi. 67,
f. 6 6) much resembles ours in the tail ; but if his two specimens be correctly drawn, be

4 BRITISH FOSSILS.

must have figured two species under the name. We cannot therefore identify the Irish
fossil with his, especially as the decided bend in the pleurae is not given in his figure ;
and we dedicate the species to Col. Portlock, who has so well elucidated the trilobites of
Ireland. Our description is drawn from his specimen.
Locality.— Lower Silurian rocks of Tyrone, Ireland.

4. 7. perovalis, Murchison, Sil. Syst. (1839) t. 23, f. 7.

/. capite gibboso, oculis remotis ; thorace quam caudd longiore, segmentis 10, axi angusto ;
pleuris paulo reflexis ad fulcrum, quod pleurar urn fere omnium ad tertium positum est, caudce
axi angustissimo, circumscripto.

In the young specimen figured the eyes are not seen, but they must be nearly as dis-
tant from the axal furrow as the width of the central lobe ; the axis of the thorax is much
narrower than the pleurae — this is maintained in the adult; the fulcrum at about one-third
in the first segment, in the next a little farther out, and from thence at an equal distance
in all the segments. Tail in youth more than a semi-circle, shorter than the thorax, with
the axis very narrow, circumscribed, and reaching about half-way down ; in the older
state it forms about a semi-circle, is flattened, and the axis does not reach so far. The
end of the axis does not indent the broadish incurved margin of the inferior side ; it does
so in /. crassicauda, which has a shorter and subtruncate convex tail, a much broader
axis to the thorax, and the eyes not nearly so remote. We have not specimens perfect
enough to characterize /. perovalis fully, but enough to show that it ought not at present
to be connected with the Swedish species.

Locality. — Llandeilo flags of the Corndon Mountain, Shropshire.

5. 7. ocularis, — n. sp.

I. capite semicirculari, utruque acutangulo, lolio centrali angusto; oculis magnis, approxi-
matis, a cervice vix dimidium diametri remotis: thoracis axi pleuris squall, his ad fulcrum
deflexis et paulitm reflexis ; pygidio ?

A species so remarkable among the trilobed division of Illanus, for the size of the eye,
that we have ventured to name it — we cannot recognize it among published species.

Locality.— Llandeilo flags, county Kildare, Ireland.

6. 7. Murchisoni, Salter. 7. Eosenbergii, ib., Mem. Geol. Surv., vol. ii., pt. 1, pi. 5, f. 6-8.

7. capite cauddque magnis, thorace brevi, anterius contracto ; capite utrdque acutangulo,
oculis ad sulcos approximatis, diametrum suum a cervice remotis ; thorace axi latissimo dis-
tincto, pleuris anterioribus brevissimis.

A species connecting the true Illani with Bumastus, having a very wide axis and very
narrow front pleurae. The axis, however, is really distinct, and the fulcrum not close to
it. There is reason to believe that the 7. Eosenbergii, to which these specimens were
referred before, is a very large specimen of 7. crassicauda : as Pander and Burmeister
have previously stated. This fine Illanus, from near the classic town of Llandeilo, we
dedicate to Sir R. I. Murchison.

Locality.— Llandeilo flags of Llandeilo, South Wales.

Notwithstanding its great similarity in external characters to Nileus, Illanus is essen-
tially distinguished by the possession of a rostral shield, a portion so designated by Bur-
meister, and peculiar to Illa:nus and Calymetie. This shield appears to be a plate inserted
between the two cheek-pieces, and separates the hypostome, or labrum, from the facial
suture. In Asaphus the cheek-pieces are united across, or in some divided merely by a
vertical suture. III. centrotus (Dalmau) has long head-spines, and in this differs from most
species of the genus, though some others are angular at the corners. Pander, and after
him Sars, described the hypostome ; it is simply oval, and by no means notched, as in
Asaphus.

The genus commenced in the Llandeilo flags, and continued to the end of the Silurian
system. We think there is not good evidence of its longer duration, though Munster cites
one or two species from Devonian rocks in Germany.

June, 1849. J. W. SALTER.

(fcilogimt f&wfoeg 0$ tbr litttd* ^ittgfa

(Silurian

I LL/tN US < BUM ASTUS) BAHRIENSIS —.JHurchisi

BRITISH FOSSILS.

DECADE II. PLATES III. AND IV.

ILLJENUS BARBZENSIS.

[Genus ILL.ZENUS. DALMAN. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitac.) Head about a quarter of a sphere ; eyes smooth,
remote ; facial suture ending on the posterior margin behind the eye, marginal or sub-
marginal in front; hypostome entire, separated from the facial suture by a trausverse
rostral shield; thorax rings 9 or 10.]

[Sub-genus Bumastus. Thorax with 10 rings, not trilobate; the axis very broad,
reaching to the fulcrum.]

DIAGNOSIS. /. (Bumastus) ovali-oblongus, valde convexus, crusta crassa ;
capitis sulcis axalibus remotis ; oculo magno prominente, vix dimidium
longitudinis suce a cervice remoto, palpebra* valde convexd ; thorace arti-
culis 10, hand trilobato.

SYNONYMS. " A new species of Trilobite," F. JUKES (1829), in Ann.
Mag. Nat. Hist., vol. ii., p. 41, figs. 8, 9, 10; "probably Isotelus" J.
D. C. SOWERBY, ib., p. 45; SILLIMAN, Amer. Journ. of Science (1832),
vol. xxiii., 1, p. 203. Bumastus Barriensis, MURCHISON (1839), Sil. Syst.,
pi. VII. bis., fig. 3 ; ib. XIV., f. 1 ; EMMERICH (1839), Dissert. 33. Nileus ?
(Bumastus) Barriensis, MILNE EDWARDS (1840), Crust., vol. iii., p. 295.
///. (Bumastus) Barriensis, BURMEISTER (1842), Org. Tril., 120 ; Ray
edition (1846), 104. Bu. Barriensis, HALL (1843), Geol. Eeport, New
York, No. 10, f. 4 ; No. 19, f. 2. [Nileus glomerinus, DALMAN, Arsberatt.
(1828), p. 136; HISINGER (1837), Leth. Suec. 16?]

Description. — Oblong-oval and very convex ; the three divisions,
head, thorax, and abdomen, nearly equal. Head a quarter of a sphere,
more pointed in front in the young specimen than in the adult, in which
it becomes obtuse. The surface of the head is even, and but slightly
marked by short converging distant axal furrows into glabella and
cheeks. Terminating these short furrows, and immediately above the
prominent upper eyelid (palpebra) is an oval space, sometimes flat of
depressed, and sometimes a little convex, where the crust is thickened
interiorly, and on which the puncta that occur so commonly on the
other portions of the crust are absent in some specimens, — its nature

* Dalman uses the term " lobus palpebralis" for the covering plate or eyelid : its varia-
tions are often characteristic.

[ll. iii. & iv.] 2 D

2 BRITISH FOSSILS.

we do not know. Eye strongly lunate, long, narrow, smooth, and sup-
ported by a very strong fold of the cheek, which forms a sort of lower
eyelid, and is most developed in age. Cornea apparently thick. The
facial suture in front of the eye runs S-shaped outwards and upwards,
turns a little beneath the margin, and then runs straight across above
the rostral shield ; it bends out sharply beneath the eye, and cuts the
margin beneath the most prominent curve of that organ. Rostral shield
a long transverse piece, deeply striate, and overhanging with a sort of
pouting lip the attachment of the hypostome. This last piece is yet
undiscovered.* Cheeks with rounded angles posteriorly, and curving
over the lower side of the head ; they are separated by the wide
rostral shield.

Thorax of 10 segments arched back, especially the forward ones,
and having the three lobes just indicated by a very slight furrow where
the fulcrum is placed, the subfusiform axis occupying more than two-
thirds the entire width. The fulcrum is far outwards, and is formed
by a short forward bend of each pleura, which then continues in the
general direction, is sharpened anteriorly for rolling, and curves forward
at its blunt end ; the foremost pleurae are rapidly shortened, the whole
of the cheeks projecting beyond them (plate 3, f. l*a).

Tail in the young about three-fourths of a hemisphere ; in the adult
more than half. The upper corners are truncated and turned down,
but there are no indications of the axal lobe. Incurved portion of the
tail not broad, but thick, deeply concave, and marked concentrically
on both surfaces by elevated lines of dots (pi. 4, f. 10, 10 a). The
whole surface of the animal is more or less punctate, and marked with
wavy imbricate lines ; they appear to vary very much in number and
position, abound near the edges of the head, but less so on its most
convex portion ; run across the thorax parallel to the course of the
rings, and on the tail are most abundant on its forward margin. On
all the articulating surfaces the lines are doubly close, but the puncta
absent. On the somewhat depressed space immediately over the fulcral
points in the head and thorax-rings, both lines and puncta vanish.
These latter, which most probably indicate the bases of short pile, are
often wide and deep (pi. 4, f. 3), and are present on the posterior
surface of the tail, where the lines are absent. The inferior eyelid
(pi. 3, f. !*£,, if so it may be called, is deeply punctate in our specimen,
but without any of the wavy lines.

Variations. — Though numerous specimens are extant, there are so
few perfect ones, that we are not able to detect any considerable variety
in the proportions. Certain Dudley specimens appear more elongate.

* Mr. John Gray of Dudley possesses an entire transverse labrum, with two tubercles,
which very likely belongs to it.

BRITISH FOSSILS. 6

Affinities.— But one is published which belongs to this section of the
genus besides our own, the Illcsnus trentonensis of Emmons (Geol.
New York, 2nd district), and through the kindness of Dr. Bigsby, the
well-known explorer of the Canadian frontier, we have seen a specimen
as large as our largest individuals of /. Barriensis, from Little Mani-
toulin Island, on Lake Huron. It differs, at a glance, from ours, in
the angularity of the posterior angle of the head, and its strongly
converging and lengthened axal furrows. Whether Dalman's Nileus
glomerinus, described in 1828, be this species, as Burmeister thinks it
may, we have no means of deciding at present.

History. — The earliest notice of the British fossil was given under
the name of " A new Trilobite from Dudley," by Mr. Frederic Jukes,
who communicated drawings and casts, and a note by Mr. J. de C.
Sowerby, to London's " Magazine of Natural History ;" the specimens
were obtained from near Barr Beacon, Staffordshire. Mr. Jukes also
communicated casts soon after to Silliman, for his " American Journal,"
and it is there stated that Mr. Sowerby had referred it to a genus
found at Trenton Falls, the Isotelus of Dekay. Professor Green, how-
ever, would not admit the identity of the two genera, and denied
the existence of the English type in America. This was quite true at
the time, but it is singular enough that the Trenton limestone should
afford afterwards another and almost identical species. Sir R. I. Mur-
chison, as is well known, founded his genus Bumastus on this Wenlock
fossil. Milne Edwards did not adopt it, and considered it closely re-
lated to Nileus ; while, however, he referred the other species of Illccnus
to Dekay's genus Isotelus. Burmeister, in 1842, placed it in its pre-
sent position as a section of Illcenus ; while the species of Nileus, which
Dalman distinguished from all trilobites (not knowing our species) by
their want of trilobation, have fallen into their true position among the
large group of Asaphus.

British Localities and Geological Range. — SILURIAN ROCKS ; Wool-
hope limestone to Wenlock limestone. Wenlock formations of Hay
Head, near Barr, Staffordshire (Sir R. I. Murchison). Dudley, Staf-
fordshire. Haven, near Aymestry, Herefordshire (Rev. T. T. Lewis).
Woolhope limestone of Littlehope, Woolhope ; and also of Nash Scar,
Presteign, Herefordshire. Wenlock limestone of Ledbury, Malvern
(Coll. Geol. Survey.)

Foreign Distribution. — Niagara group of New York (Hall). A
species very like it was found near Hohcnholm, by Eichwald (Urwelt,
Russland, Heft, 2, 59), but it is not quoted from Norway or Sweden.

BRITISH FOSSILS.

EXPLANATION OF PLATE III.

Fig. 1. Old individual from Barr, in the possession of Miss Jukes, of Birmingham.

Fig. 1*. Side view of the same, showing the shortened foremost pleurae (a), and the
inferior eyelid (6).

Fig. 2. Side view from a fine coiled specimen in the cabinet of John Gray, Esq.,
Dudley.

Figs. 3, 3*. Two views of a young one ; in the cabinet of Augustus Lewis, Esq.

PLATE IV.

Fig. 1. The dissected figure, a, head ; b b, cheeks ; c, thorax segments ; d, tail.

Fig. 2. Portion of surface above the eye, showing the wavy lines and puncta.

Fig. 3. Ditto, with puncta larger than usual.

Fig. 4. Magnified pleurse, with lines and puncta.

Fig. 5. Part of tail, the puncta only present over the hinder portion of it.

Fig. 6. Pleura magnified, showing the fulcrum a, the backward bend at b, the sharpened
forward edge c.

Fig. 7. Large head from Littlehope.

Fig. 7*. The same, lower side, a, rostral shield; b, rostral suture (Burmeister).

Fig. 8. Shows the thickened portion of shell just above the eyelid at a ; impression of it
on the stone beneath at b. (In this specimen it is destitute of puncta.)

Fig. 9. Side view of part of tail ; at a, the fulcral point ; b, the articulating surface,
with lines, but not puncta.

Fig. 10. Incurved portion of tail ; the inward surface with elevated granulate lines.

Fig. 11. A ditto, magnified.

The specimens figured in this plate are in the Geological Survey Collection.

The section Bumastus is related to the more typical species of Illanus, just as Nileus,
of Dalman, is to his Asaphus palpebrosus. The distinct trilobation has vanished, and the
axis is so wide as to reach the fulcral point, and be nearly coincident with it. There is
a slight backward bend of each pleura just before the fulcrum, which serves to steady the
articulation of the piece behind by overhanging it a little, while this piece, in turn, over-
hangs the preceding at the fulcrum, precisely as in the articulation of the abdomen of the
lobster and cray-fish. Beyond the fulcral point the pleura is always more or less sharp-
ened, to pass under the preceding joint in the act of bending ; and, as in this operation,
the back is lengthened, and the soft parts of the axis would be exposed by the separation
of the segments, a convex articular portion is added on the forward edge of each segment,
which fills the gap, and retires beneath the preceding joint, when the animal is extended.
This is the structure of all trilobites which have been observed to bend or roll, and it is
similar to that met with in recent Crustacea.

The subgenus is known in the Lower Silurian rocks of America, and the Upper Silurian
of Britain.

J. W. SALTER.
Jane, 1849.

»lfl|juai §&mtiep vftfyeHmteb &ttt0ft<nn.

j^ai

^ Silurian;

A S A P H U S TYRAN

BRITISH FOSSILS.

DECADE II. PLATE V.

ASAPHUS TYEANNUS.

[Genus ASAPHUS. BRONGNIART. (Sub-kingdom Articulata. Class Crustacea. Order
Eutomostraca. Family Trilobitse.) Eyes large, smooth. Facial suture marginal or
supramarginal in front, and ending on the posterior margin. No rostral shield. Hypostome
strongly bilobed. Body rings 8.]

[Subgenus Basilicas, Salter. Facial suture marginal in front ; head but slightly lobed ;
pleurae furrowed transversely ; tail large, with axal and lateral furrows.

DIAGNOSIS. — A. (Basilicus) ovalis ; capite semicircitlari, angulis in
spinas breves productis ; cauda parabolicd, late marginatd, regulariter con-
vexa, apice rotundato nee acuto ; axi distincto, sublineari, angustot mulli-
costato, apice abrvpto; lateribus multicostatis.

SY.NONYMS. Asaphus Tyrannus, MURCHISON, Silurian Syst. (1837),
pi. xxiv. and pi. xxv., f. 1. Ogygia Tyrannus^ EMMERICH, Dissert. (1839),
29. Asaphus Tyrannus, MILNE EDWARDS, Crust. (1840), 3, 310. EMME-
RICH, Leonhard and Bronn's Neues Jahrbuch 1845 (translated in ' Scientific
Memoirs,' vol. iv. (1845), 273). [not of BURMEISTER, Organ. Trilob.
(1843), t. 5, f. 4. Ray edition (1846), 108.]

A remarkably perfect specimen in the cabinet of W. Day, Esq., of
Hadlow near Uckfield, and specimens in the Geol. Survey collections
displaying the parts of the mouth, enable us to present a complete
description of this famous, but apparently local trilobite.

Description. — Length 11 inches ; breadth 6| inches. General form
nearly a true oval, moderately convex ; the head semicircular, the tail
longer and parabolic. Head smooth, with a slight concavity marking
off the margin, produced at the angles into short spines which reach the
third thoracic segment. Glabella clavate, defined in front only ; the
forehead lobe large, protuberant, and nearly round : beneath it, and at
the level of the front of the eye, is the uppermost of three obscure
oblique furrows. There is at the base of the glabella a tubercle, and
beneath it an impression marking the place of the neck furrow. Eyes
rather large, much arched, placed behind the middle of the head, and
close to the glabella ; the base of the eyelid is constricted, the lentiferous
surface is broad and smooth, and beneath the cornea there are very

[II. V.] 2 E

BRITISH FOSSILS.

numerous lenses,* not quite closely set. Facial suture ending on the
posterior margin, at the inner third of the width of the cheek, and in
front of the eye turned outwards in a sigmoid curve ; it cuts the front
margin beyond the parallel of the eye, and continues exactly along the
edge of the shield.

The hypostome is semicircular at its base, which is moderately broad ;
it has a squarish tumid centre surrounded by a strong furrow, and is
deeply divided at the apex into two ovate-lanceolate forks, between
which the shelly plate turns strongly inwards : there is an oval circum-
scribed tubercle at the origin of each, most distinct on the inner
surface.

Thorax of eight moderately arched rings, the axis not strongly
marked and as broad as the pleura ; these latter are furrowed for
three-fourths of their length, and are curved down, but scarcely bent
backward, at the obscure fulcrum, which in the hinder rings is placed
at about one-third away from the axis, but much nearer to it in the
forward rings ; the anterior edge of each pleura is sharpened, and its
termination square.

Tail parabolic, its width at the broader end one-fourth greater than
the length (it appears nearly equal), regularly convex, not sunk in the
middle ; axis flattened forwards and prominent behind, terminating
abruptly at four-fifths the length of the tail, and ribbed throughout by
about 15 furrows. The sides are furrowed for about half their width
by 12 or 13 oblique parallel sulci, which end abruptly at the edge of
the broad concave margin ; the uppermost furrow is much stronger
than the rest. The incurved lower surface of the tail occupies rather
more than the breadth of the smooth upper border, and folds round the
end of the axis which indents it. The fine lines on this incurved border
are not truly concentric with the edge, but appear to branch from an
imaginary line along the middle or most concave part. The space left
between the upper and lower borders is shallow. On the upper crust
of the tail the wavy lines are interrupted and inosculate ; they arch
over the axis with the convexity of the curve forwards : on the lateral
lobes the curve is re versed, f The same arrangement is seen on the
thorax rings, — at the ends of the pleurae they turn upwards, and fig. 8
shows the longitudinal disposition of these lines on their under sides.
On the head similar lines occur, but we have not specimens to show it
well ; the hypostome has them obliquely on the forks (fig. 4).

* On a specimen lent by Mr. Day, which presents only the lower half of the eye,
the number and arrangement is such, that judging from analogy with A. Powisii, the eye
of which is very much like this, there must have been 6000 lenses, or probably more.

t Burmeister has figured a good example of this arrangement of the sculptural lines or
e tail of an Asaphus in his "Zeitung fur Zo<»logie,'' &c., 1 Band, 1848, t. 1, f. 19.

BRITISH FOSSILS. O

Variations. — Some individuals (perhaps females) are much more
convex than others ; in some the margin is abruptly concave ; our
figured specimen is depressed. The number of lateral ribs to the tail
varies considerably, they do not seem to become more numerous by
age. The forks of the hypostome are long or short. The ornamental
lines which are so conspicuous in the external cast (PI. 24, Sil. Syst.)
exist, though less deeply sculptured, in all ; the internal cast, which is
more commonly found than perfect specimens, does not show them
distinctly.

Affinities. — The specimen figured in Burmeister's work appears by
his description to have been from a " boulder of red limestone," and
hence it is very probably a worn specimen of A. heros (Dalman), from
the red limestone of Kinnekiille, Gothland. It is unfortunate that the
author should have transferred the sculpture of A. tyrannus to this
figure, for the axis is constricted in the middle and depressed, and the
lateral ribs long ; it is in fact a pretty good figure of A. heros, except in
the rounded tail ; in Swedish specimens the tail is pointed and the axis
percurrent. There is also a species in the lowest Silurian limestone of
New York so like ours, that we do not know how it is distinguished ;
there ate, however, but seven or eight distinct ribs on the axis, and
those on the sides are said to be duplicate ; we refer to A. marginalis
(Hall), described in the Palaeontol. New York. This is the more inter-
esting, as the Asaphi of North America belong generally to the group
Isotelus* The species which most nearly resembles A. tyrannus, and
which I referred to it in Prof. Sedgwick's papers in the " Geological
Journal," is the A. Poivisti, very common in the slates of North Wales.
The specimen of this latter species figured in the " Sil. Syst." is much
compressed, for the species is really more convex than that here
described, with deeper furrows on the pleurae, which are arched forward
at their ends ; and the tail axis is wide above, rapidly contracting in
width and becoming quite indistinct, its end only prominent ; the surface
seems smooth ; the sides of the tail have a very strong uppermost
furrow ; the remaining furrows are faint. Fine specimens of A. Powisii,
in the collections of the Geol. Survey and of Mr. Sharpe, show very
numerous lenses (about 7000) on each eye.

History. — It appears not to have attracted the notice of Llhwyd,
although it is quite as common at Llandeilo as the Qgyyia Buchii, of
which he figured specimens ; nor does it seem to have been noticed
by any writer on trilobites previously to the publication of Sir R. I.
Murchison's work. Emmerich, in his Dissertation, showed how close he
considered its afiinities to be with Oyygia, by transferring it to that

* The young animals of even this group, according to Hall's figure, are trilobed and
ribbed in the tail ; but that can only be in a very young state.

4 BRITISH FOSSILS.

genus. In 1845, however, he restored it to Asaphus, though he evi-
dently had not observed the characteristic labrum. Burmeister appears
not to have been acquainted with the species, since in both editions he
confounds it with what we believe to be a specimen of A. heros, and even
suggests, in his Appendix, that Murchison's smaller figure might prove
to be A. extenuatus. He notes that it appears anomalous for Asaphus
to have such distinct ribs on the tail ; and indeed this peculiarity is one
of the indications of its affinity to Ogygia, which we think confirmed by
the course of the facial suture.

Localities and Geological Position in Britain. — LLANDEILO FLAGS. —
Limestone of Wrae, Peebleshire ? (Geol. Society's Coll.). Coniston
limestone, Westmoreland ? Craig-y-Glyn, Berwyn Mountains, in Bala
limestone (Sedgwick) ; Meadow Town ; Shelve, &c., in the Longmynd,
Shropshire ; Carneddau Hill, Builth, Radnorshire [J. W. S.] ; Llandeilo,
and many neighbouring localities in Caermarthenshire ; Llampeter
Felfry, Pembrokeshire [Murchison] ; Narberth ; Mydrim ; Sholeshook ;
Lann Mill, Pembrokeshire (Phillips). It is remarkable that it does not
occur in Ireland.

Foreign Distribution. — It is quoted by Sir R. I. Murchison from
Northern Europe [Quart. Geol. Journal], but with the understanding
that A. heros, Dalm., was intended. A. marginalis, Hall [Palseont.
New York, pi. 4, bis, f. 15], may be the same as our species.

EXPLANATION OF PLATE V.

Fig. 1. Perfect specimen. Llandeilo. (Collection of W. Day, Esq.)

Fig. 2. Outline of central portion of head, showing the constricted eyelids. Lann Mill.

Fig. 3. Portion of head, with the base of the eye, a. Llandeilo (Mr. Day's Collection).

Fig. 3*. Magnified portion of a cast from the same, which would represent the surface
of the eye when the smooth cornea is removed.

Fig. 4. Perfect hypostome, with the upper processes (a a). Lann Mill.

Fig. 5. Variety of the hypostome, with shorter forks. Golden Grove.

Fig. 6. Punctate exterior surface of part of hypostome ; the lineated surface is shown
in fig. 4.

Fig. 7. Upper surface of a thorax joint. St. Clears.

Fig. 8. Under surface of ditto, showing the extent of the incurved portion b, b.

Fig. 9. Part of thorax of a large individual, with deep sculpture. Golden Grove,
Llandeilo.

Fig. 10. Tail of young individual. Llandeilo.

Fig. 11. Incurved part, under side of the tail, bounded by the lines a, a, and deeply
indented by the axis. Clog-y-frain. (Sir R. I. Murchison's Cabinet.)

June, 1849. J. W. SALTER.

OCYCIA HI-CHI! -Branqniart.

BRITISH FOSSILS.

DECADE II. PLATE VI.

OGYGIA BUCHII.

[Genus OGYGIA. BRONGNIART. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitse.) Eyes large, smooth ; facial suture cutting the pos-
terior margin; no rostral shield or vertical suture; hypostome entire; body rings 8;
tail large.]

DIAGNOSIS. O. ovalis, glabelld angustd utrinque quinquesulcatd ; oculis
ad medium capitis ; suturd faciali ad frontem marginali ; spinis posticis
brevibus ; hypostomate obtuse acuminato ; thoracis axi bis pleura angustiore ;
caudas axi longo abrupto ; sulcis lateralibus 12 duplicaiis, prope marginem
angulatim deflexis.

SYNONYMS. LLHWYD (1698), Philosoph. Transact., vol. xx., 279, tab.
addit., f. 15. Buglossa curta strigosa, ib., Ichnograph. Brit. (1690), Epist. 1,
t. 22, f. 2. Trilobite from Llanelly, PARKINSON, Organ. Kern. (1811),
v. iii., t. 17, f. 13. Asaphus De Buchii, BRONGNIART, Crust. Foss. (1822),
t. 2, f. 2. Trilob. De Buchii, SCHLOTHEIM, Nachtr. (1823), ii., 34
(excl. the locality, " Norway.") Asaph. Buchii, Dalm. Palead. (1826), 68.
J. D. C. SOWERBY, in Loudon's Mag. Nat. Hist., 1829, vol. ii., f. 27.
BUCKLAND (1836), Bridgwater Treatise, t. 46, f. 7. MURCHISON (1837),
Sil. Syst., t. 25, f. 2. QUENSTEDT, Wiegm. Archiv. (1837), vol. iii., 1,346.
EMMERICH, Dissert. (1839), 28. MILNE EDWARDS, Crust. (1840), 3, 309.
BURMEISTER, Org. Trilob. (1843), t. 1, f. 2, [facial suture wrongly figured.]
Kay edition (1846), p. 59. CORDA, Bohm. Tril. (1847), t. 4, f. 39 [bad.]

JUNIOR. Trinucleus? asaphoides, MURCHISON, Sil. Syst., t. 23, f. 6.

MILNE EDWARDS, Crust., v. iii., 333.

Description. — Length occasionally near seven inches, generally three
or four ; proportion of length to breadth from 6:5 to 6 : 4, a consi-
derable variation. General form a broad depressed oval, the head
nearly semicircular and as long as the thorax, the tail semi-elliptical
and longer than either ; glabella at its base occupying one-fourth or less
of the width of the head, broader and more convex above, and a little
pointed in front ; it extends nearly to the front margin, and is marked,
a little within each side, by a longitudinal depression, which is curved
with the convex side inwards. Along this hollow lie five pits, \\hich
represent the glabella furrows ; the basal one is the neck furrow, that
[n. vi.] 2 F

2 BRITISH FOSSILS.

above is placed near the centre of the glabella, the other three re-
cede more, the uppermost coming just above the eye. Eyelid large,
semicircular, and not touching the glabella. The facial suture above
the eye is curved outwards a little to reach the margin, along which it
runs for some distance ; beneath the eye it curves largely outwards,
and cuts the posterior edge just within the border. The latter is wide
and striate, more or less concave, and marked off by a distinct marginal
furrow. Eye placed halfway up the head, smooth, the lentiferous sur-
face broad, its minute structure is not yet known. Head angles not
produced below the fourth body segment. Hypostome broad above,
narrowing below, where it is suddenly and obtusely pointed ; the
centre is gently raised, and a furrow runs down each side ; there are
two transverse furrows near the apex, with compressed tubercles between
them. Thorax with the axis gently convex, variable in proportion, but
seldom more than half the width of the pleurae. These are flattened,
furrowed along the upper margin as far as the fulcrum, at which there is
an obtuse bend (fig. 2, c, c), the furrow diverges from the margin
here, and does not quite reach the recurved and pointed extremity ; it
becomes widest immediately beneath the fulcrum, and from the lower
margin of the pleura? at this point a narrow ridge runs obliquely up-
wards, and meets it. Tail varying from little more than a semicircle
to a half-ellipse, very gently convex ; the axis gently tapering, ribbed
by about 13 or 14 furrows, which have a downward bend in the middle ;
its obtuse tip projecting. Lateral furrows at nearly right angles to the
axis, angularly bent downwards at the place of the fulcrum,* interlined
all the way by fainter furrows, and leaving but a narrow flat margin.
Incurved under portion of the tail narrow, closely striate, not indented
by the axis ; the upper side has a striate band of the same width, which
is indented by every rib of the tail. The inferior striated band is con-
tinued (of the same width) along the ends of the pleura?, and the stria?
run in the same direction, while, on the upper surface, they are trans-
verse, and reach further inwards. Numerous fine stria;, arched upwards,
cover the axis. The cheeks appear to be nearly smooth, but the gla-
bella is covered by fine, short, broken, almost microscopic lines. The
hypostome is strongly and concentrically striate.

Variations. — It varies in convexity, proportionate length, and hi the
width of the axis ; this latter is sometimes, though very rarely, more
than half the breadth of the pleura? — generally half, frequently less than
half. A pair of tubercles on each segment of the axis is present ; they
are distinct and strong in some specimens (fig. 6), and faint in others.

* The tail, consisting of anchylosed segments, preserves traces of nearly all the cha-
racters of the thorax ; the strong furrows are analogous to the furrows of the pleurse, the
fainter lines between them to the joints.

BRITISH FOSSILS. 3

Affinities. — From O. Guettardi it is known by its less elongate and
more oval shape, and greater width of pleurae in proportion to the axis ; in
O. Guettardi they are but once and a-half the width. The axis of the
tail is longer, and has 13 instead of 9 ribs, and is abrupt, not attenuated
at the tip ; — in O. Guettardi it extends but three-quarters the length.
It has, also, duplicate, bent, and more numerous side furrows ; the other
has but eight or nine straight simple ones ; the hypostome also is sub-
conical, not dilated laterally. O. dilatata, Brunnich (not of Portlock),
which seems to have been frequently held as a variety of O. Buchii, has
the glabella short, with its lobes crowded down towards the lower part,
and the eyes remote. The facial suture behind the eyes appears much
less arched in Sars' figure. He also describes the tail as with 10 ribs,
separated by broad furrows. The labrum of 0. dilatata, according to
Sars' figure, is but slightly different from that of the British species ;
but an important difference resides in the facial suture, which, in O.
dilatata, is within the front margin on the upper side, but in O. Buchii
is along the edge itself, as in Asaphus Tyrannus.

History. — The earliest mention we can find of Trilobites is concern-
ing this species, and is that which all writers on these fossils have quoted.
Mr. Edward Llhwyd, in a letter to Dr. Martin Lister, of the Royal
Society (1698) writes " concerning several regularly figured stones lately
found by him." " The 15th," he says, " we found near the Lhan
Deilo*, in Caermardhinshire, in great plenty, it must, doubtless, be re-
ferred to the sceleton of some flat fish ;" but, a few lines after, " Not
that these, or any other marine terrestrial bodies were really parts of
exuviae of animals, but they bear the same relation to them as fossil
shells to marine ones," &c. This latter opinion he takes care to main-
tain in his " Lithophylacii Brittanici Ichnographia " (1699), where he
again says, the specimen represents only the skeleton of a sole fish, and
wants the tail, and he marvels that the " Piscis Icon " should be raised
above the surface of the stone, " ac si verus piscis esset." It is curious
that Brongniart should have placed this species in his heterogenous
group Asaphus, at the very time he was founding Ogygia, as he ap-
pears to have recognized the latter genus more by its marked habit
than by any positive characters. He probably meant to unite A. dilatatus
with A. Buchii. Dalman distinguished them, but with doubt, in 1826,
and gave a figure of the Norwegian fossil from a plaster cast ; and had
not Sars, in 1835, given a complete description, and a good figure of

* Fig. 9, of the same communication, is often quoted as belonging to Trinucleus. We
have no doubt it is T. Caractaci, as that is the common species there ( T. fimbriatus is
found at Builth) besides, the distinct dots in the fringe identify it with the former species.
Fig. 8 appears never to have been quoted, yet it is a tolerable representation of Cybele
verrucosa, Dalman, and it has been figured again without a name by Brongniart, plate 4,
f. 11, from the same locality, where it abounds, and is the only species of the genus there.

4 BRITISH FOSSILS.

the head, the identity might still have been maintained. The hypos-
tome of this species was first represented in Sir R. I. Murchison's figures.
We have ascertained, by personal inspection, that the Trinudeus Asa-
phoides of his work is the young of O. Buchii. Quenstedt, 1837, unfor-
tunately got hold of two specimens with seven rings ; whether an accidental
variety, or as Burmeister thinks, one occasioned by the slipping of one
ring under the others, it is difficult to say. Quenstedt, however, relied
on these, and Dalman's 7-ringed specimen of O. dilatata, and asserted the
same number for O. Guettardi. But the error in both cases led him
to see the generic affinity between these two allied species, and he dis-
tinctly says that their union with the typical Asaphi is unjustifiable.
Burmeister, in his first edition, set the number of rings right, but con-
founded O. dilatata, which Sars had well distinguished in Oken's
" Isis," (1835), with our species, and adhered to this view in the Ray
edition (1846). Emmerich had, in the mean time, spoken of them as dif-
ferent species, and figured O. dilatata in Leonhard and Bronn's " Neues
Jahrbuch," for 1845. Corda still maintains the error of the seven rings.

British Localities and Geological Range. — LLANDEILO FLAGS only.
Not yet known in North Wales ; the localities given for it in the " Geol.
Journal," vol. i., p. 20, &c., are erroneous, and were stated to be so in
vol. ii., p. 128. It abounds in the distorted slates at Shelve and Hope
Mill, Sliropshire (Sir R. I. Murchison) ; Rorrington, Middleton, and
Meadowtown, Shropshire ; Builth, Radnorshire ; Llangadoc and Llan-
deilo, Caermarthenshire (Geol. Survey Coll.) Haverfordwest ; Muscle-
wick Bay, Pembrokeshire (Phillips). Not yet found in Ireland.

Foreign Distribution. — La Couyere, Bain, &c., near Rennes, in the
Cote d'or (M. Rouault). In the north of Europe O. dilatata takes its
place.

EXPLANATION OF PLATE VI.

Fig. 1. Perfect specimen from Builth (the glabella hardly pointed enough in front).

Fig. 2. Same specimen dissected ; at a the slight ascending furrows which cross the
neck segment are seen ; b b, cheeks or wings; c c, fulcral points of the pleurse ; d, tail.

Fig. 3. Under side of head in front, with the hypostome b attached to the continuous
under portion a of the cheeks ; Builth.

Fig. 4. Young specimen from Builth.

Fig. 5. Border of the tail, the inflected striate portion rendered wavy by projecting
further inwards on each rib.

Fig. 6. Variety, with the tubercles on the axis strong ; Llandeilo.

All the specimens in the Geological Survey Collections.

1849. J. W. SALTEU.

tied |Kn$&nn ,

OCYCIA POBIIOCKII ,W/,v.

BRITISH FOSSILS.

DECADE II. PLATE VII.

OGTGIA PORTLOCKII.

[Genus OGYGIA. BRONGNIART. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitse). Eyes large, smooth; facial suture cutting the pos-
terior margin ; no rostral shield or vertical suture ; hypostome entire ; body rings 8 ; tail
large.]

DIAGNOSIS. O. ovali-oblonga ; capitis margine angusto ; glabella genis
latiore, obscure lobatd ; oculis ad anteriorem partem capitis positis ; sutura
faciali ad frontem marginali ; caudce axi lato brevissimo.

SYNONYMS. Asaphus dilatatus, PORTLOCK (1832), Geol. Rep., Tyrone,
&c., pi. 24, f. 2 (not of Dalman). Ogygia dilatata, PHILLIPS, Memoirs
Geol. Survey (June, 1848), vol. ii., pt. 1, 239.

Description. — Length 3^ inches ; width 2i inches ; often larger.
General form nearly flat, ovate, widest in front. Head forming rather
more than a semicircle, considerably longer and wider than the tail,
but about as long as the thorax ; the glabella is as wide as the cheeks
below, and separated by slight furrows from them ; it widens and over-
hangs the eyes above, and is abruptly bent down in front, where the
margin is hardly visible. For nearly two-thirds of its length the gla-
bella is marked by lateral furrows, irregular in direction, dividing it
(apparently) into four lobes, exclusive of the forehead and neck lobes.
The neck lobe b is broad, and rises higher on each side than in the
middle ; it has two oblique sunk lines, c c, rising from the lower angles,
which appear to divide it into a pair of lobes ( O. Buchii has the same
marking). Above this lobe lies the more contracted basal one g,
which does not reach to the margin of the glabella. The second lobe, /t,
is wider and more oblique than the third, z, which is very faintly divided
from the wide transverse forehead lobe a. The fourth lateral lobe, so
distinctly marked in 0. Buchii, is absent in this species. Eyes mode-
rate, placed very high up, towards the termination of the facial suture
on the margin ; eye-lid semi-lunate, but not constricted above or below ;
eye line turning a little out above the eye, beneath it obliquely down-
wards and outwards, cutting the posterior margin at about half the
cheek's width ; wings moderately large, with a narrow border and a
[n. vii.] 2 G

2 BRITISH FOSSILS.

small spine. Hypostome with the centre gently swelled, and with dis-
tinct concentric furrows on the sides ; apex ?

The first and last thorax rings are somewhat narrower than those of
the middle ; the axis is widest at top, and there only a little narrower
than the pleurse. It is not arched, but flattish, and marked by indis-
tinct tubercles on the sides and middle. The pleurae are straight ; the
fulcrum indistinctly marked about half-way along them ; the divisions
between the segments not nearly so conspicuous as the oblique straight
furrow which reaches nearly to the end of each. The ends of the
pleurae are recurved and pointed, the foremost ones perhaps not quite
so strongly as in our larger figure, the hinder ones as much as in fig. 2*.

Tail a semicircle, with the upper angles rounded off; the axis hardly
more than two-thirds the length, flattened, conical, the end a little
pointed. There are about five distinct ribs on the axis, each obscurely
trituberculate. Lateral furrows four or five, very oblique, the two
uppermost sharp and deep, reaching more than half across the side, with
a secondary one between them, the two or three last very short and
faint. Margin flat. Whole surface of tail crossed obliquely by lines
which all run down from the upper angles inwards, except near the
edge, where they are concentric ; the incurved portion of the tail con-
centrically striate, broad, and indented by the axis. On the pleurae
the lines are longitudinal, and form a broad band crossing the segments.
We do not know their direction on the head ; the hypostome, however,
is strongly marked by raised concentric threads.

Variations. — In the young state the middle lobe of the thorax and
tail is narrower (of the latter considerably so), and therefore longer
proportionally than in the adult ; thus, in our smallest specimens,
fig. 3, the pleura? are once and a half as wide as the axis ; in fig. 4,
which is older, nearly as wide in proportion. In this stage the tail axis
is not visibly annulated, but the number of lateral ribs is the same as
in older specimens, about four ; the upper one is not, however, dupli-
cate. The glabella in the youngest specimens is very obscurely lobed,
and the eyes are thrown even further forward, close to the very narrow
border in front of the glabella. The latter is not incurved in front.

The most interesting point about these young Oyygice is, that they
appear to confirm the supposition of the number of segments increasing
with age. Fig. 3, the youngest, has but four segments to the thorax,
and there is no appearance of displacement, the head is not shifted at
all. In fig. 4, a little older, there are seven rings, nor can we think
there is displacement in this case. The tail has turned a little, as on a
pivot, pushing the front edge on one side a little under the last ring,
but it has opened from that ring on the other side. Had a ring been
shifted off, and lost in the stone, we might have expected to see an

BRITISH FOSSILS. 3

impression of part of it on this exposed side — but there is none. And
the probability that we have in this case the whole number of rings
is strengthened by observing what takes place in one a little older,
fig. 5*, for in this the last segment is very narrow, and appears to be
in course of development.* We have no perfect very young spe-
cimens of O. Buchii, and therefore the point is still open to observation
in this genus, in which occasional specimens have certainly been found
with seven rings, as noticed by Quenstedt, Dalman, and Burmeister.
The usual number is eight.

Affinities. — Its identification with O. dilatata by its discoverer, Port-
lock,! is easily understood by reference to his very imperfect original
specimen, which he saw clearly was distinct from O. Buchii. With
Dalman's figure, too, there is more similarity than with the better
figures published since by Sars (Oken's " Isis," 1835), and Emmerich
(" Scientific Memoirs," vol. iv.) Our species differs from the Swedish
one essentially in the broad glabella, narrow head margin, and forward"
eyes. The proportions of the caudal axis and the lateral ribs of the
tail are altogether different, but the above-mentioned characters of the
head will suffice.

British Localities and Geological Range. — LLANDEILO FLAGS. Large
and fine specimens were obtained in abundance at Newtown Head,
Waterford ; smaller ones are common at Builth, Radnorshire.

Foreign Distribution. — Not known. Dalman's figure of A. dilatatus
is more like our species than the representations given by Sars and
Emmerich, but we take it for granted these authors figure Brunnich's
species, as their specimens were from Christiania.

EXPLANATION OF PLATE VII.

Fig. 1. Large, but not full-grown individual. Newtown Head, Waterford.

Fig. 2. Same, or similar specimen, dissected.

[The letters on the head are placed in the order of those in the Mem. Geol.

Survey, vol. ii., pt. 1, p. 334.]

a, Forehead, or front lobe ; 6, neck lobe, traversed by a pair of oblique lines c e,
which mark the extent of the articulating surface of the first thorax joint ; g,
basal, or first lobe; h, middle, or second lobe; i, upper lobe, third; j, posterior
margin, or lateral neck lobe ; C, free cheek, or wing ; o, margin.

Fig. 2*. Thorax ring of ditto ; cc, place of fulcrum ; e, an oblique line running up
wards to the furrow (as in O. Buchii).

* We believe this increase in number is not a solitary case. The figured specimen of
Trinuclens Lloydii, Murchison, has but five rings, and seems perfect. It may be peculiar
to certain genera. Burmeister has suggested it in the case of Paradoxides bohemicus.

f We have great pleasure in dedicating the new species to Lieut. Col. Portlock, whose
careful and elaborate treatise on the Irish trilobites will be always valued by the British
student. It was not only the best, but, at its publication, was the only English work
containing extended views of the generic affinities.

4 BRITISH FOSSILS.

Fig. 2**. Tail of ditto ; /, line marking the edge of the thin incurved portion of tail
[the lines that cover the tail in this figure are those of the upper surface] ; g, intermediate
furrow between 1st and 2nd.

Fig. 3. Youngest specimen, with four body rings. Builth.

Fig. 3*. The same magnified, to show the narrow caudal axis.

Fig. 4. One rather more advanced, with seven body rings. Builth.

Fig. 4*. The same, &c., magnified ; shows the tail a little turned aside.

Fig. 5. Still older ; the eyes very forward ; eight rings. Builth.

Fig. 5*. The same, magnified : shows the last thorax segment as yet imperfectly deve-
loped a.

Fig. 6. Specimen of intermediate size, with short axis. Waterford.

Fig. 7. Imperfect hypostome ; a a, concentric furrows. Waterford.

Note on the Genus.

The near affinity of Ogygia with Brontes has been perceived by Emmerich, who, in his
excellent paper, " On the Morphology and Classification of Trilobites," * placed it next to
that genus. The number of segments differs, 10 for Brontes, 8 for Ogygia; Brontes, too,
is sometimes very convex, while Ogygia is flat ; the shape of the glabella and caudal axis
differ materially, and there was no genus known which could fill up the interval between
the two genera. Both are expanded forms, characterized by large and strongly radiated
tails, and flattened glabellse, and by an obtuse, entire, furrowed hypostome. We are,
therefore, fortunate in being able to publish a species of Ogygia whose characters link the
genera much closer than before, and which, perhaps, might be regarded rather as a new
generic form, but that its habit is quite that of Ogygia. If we knew more species of the
genus, we would propose sub-genera for it, and might divide it into —

1. Glabella indistinctly lobed ; facial suture within the margin. O. Desmarestii,
Brongn. O. Edwardsii, Kouault.

2. Glabella distinctly lobed ; facial suture within the margin. O. dilatata, Dalm.

3. Glabella narrow ; facial suture on the margin. O. Buchii, Brongn. O. Guettardi,
Brongn.

4. Glabella broad ; facial suture marginal. O. Portlockii.

There are three or four undescribed British species of Ogygia, but at present we know
them only by fragments.

J. W. SALTER.
June, 1849.

* Leonhard and Bronn's " N. Jahrbuch," 1845, translated in Taylor's " Scientific
Memoirs," vol. iv.

CALYMENE

BRITISH FOSSILS.

DECADE II. PLATE VIII.

CALYMENE TUBERCULOSA.

[Genus CALYMENE. BRONGNIAHT. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitae). Axis distinct ; glabella lobed, narrower anteriorly ;
facial suture dividing the posterior head angles, submarginal in front ; a rostral shield ;
eyes supine (with a thin cornea ?) ; thorax of 13 rings, formed for rolling.]

DIAGNOSIS. C.lata, depressa, alutacea; margine frontali capitis pro-
duclo recurvo, genis gibbosis, glabella depressd ; thora.ce axi angusto, pleuris
plants usque ad fulcrum, quod ad dimidium anterius, ad tertium posterius,
positum est ; caudd laid, superne depressd, lateribus abrupte deflexis ; axi
conico, subplano, 7-8 annulate, costis lateralibus 5, plants, sulcis acutis.

SYNONYMS. C. Blumenbachii vera ? a. tuberculosa, DALMAN (1828),
p. 36? (not tab. 1, f. 2). C. Blumenb., var. a. tuberculosa. HISINGER
(1837), Lethaea Suecica, 10? (not tab. 1, f. 3). C. Blumenb., MURCHISON,
(1839), Sil. Syst., pi. 7, f. 5 only. C. tuberculosa, SALTEB (June, 1848),
" Memoirs of Geol. Survey," vol. ii. part 1, pi. 12.

Almost every author who has written on Calymene Blumenlachii has
hinted his belief that two or more species were to be recognized among
its protean forms ; yet, except Colonel Portlock, who separated the C.
brevicapitata in his report on the fossils of Tyrone, no one has done more
than point out varieties. An extended examination of very numerous
specimens convinced us that three distinct species were known in Eng-
land, and their characters were detailed in the 2nd volume of the
" Memoirs of the Geological Survey." Still further investigation of
intermediate forms has shaken this opinion again, and we are at present,
wholly in doubt whether the striking differences about to be pointed out
mark only a distinct variety, or are of specific value. At all events, in
giving a typical species of this genus, we would rather present the
reader with a new and well-marked form, than with one so familiar as
that of the famous « Dudley fossil."

Description. — Length, about 2± inches, width, H inch. Whole sur-
face equally and minutely scabrous. General form broad for the genus,
not much attenuated posteriorly, depressed. Head short, wide ; the
[n. viii.~] 2 H

2 BRITISH FOSSILS.

glabella not more prominent than the cheeks, and much narrower, con-
tracted in front, and separated by a deep furrow from the front margin :
it has three lobes on each side, the basal one large, the middle one
nearly spherical, the third minute ; the forehead lobe is small, the neck
lobe large and prominent. The neck furrow is continued nearly to the
posterior angles, which are rounded. Cheeks gibbous, often more ele-
vated than the glabella, bearing the small eyes on their most prominent
part. These are placed opposite the middle lobe of the glabella, and at
some distance from it. A strong deep furrow separates the cheeks
from the glabella, except opposite the eye, where a buttress is thrown
across from the cheek, touching the middle glabellar lobe. The wings are
strongly bent downwards, and even inwards on the under surface of the
head, and the anterior margin is much recurved, and produced into a
snout. On looking at the under view of the head, the margin appears
greatly bent, and in the angle so formed the curved rostral shield, half
as long as broad, is inserted ; beneath this is attached the hypostome,
which is squarish oblong with the terminal angles rounded, strongly con-
vex forwards, the convexity terminating in a compressed tubercle ; one or
two concentric lines, as if of growth, mark the surface, which is also
scabrous, like the general crust of the body. The axis of the 13 body
rings is convex, but narrower than the pleurae, and constantly tubercular
on the sides. The pleura? are horizontal half way, and then strongly
decurved ; their ends rounded posteriorly, and bent forward. Fulcrum
distant from the axis, about half way from it near the head, — at one-
third, or rather less, behind. Pleurae sharply furrowed, the forward or
fulcral half somewhat narrower than the posterior. Tail nearly semi-
circular, with the front angles truncated, evenly and gently convex, the
axis not prominent, the sides decurved strongly towards their edges.
Axis not percurrent, narrow, conical, with seven rings, and a terminal
boss. Lateral ribs flattened, separated by sharp, narrow furrows, start-
ing at a wide angle from the axis, and curved back on the sides, simple,
or but rarely marked by a central line near their ends, —not bifurcate, as
in C. Blumenbachii.

Junior. — The proportions of the axis to the sides and the struc-
ture of the pleurae are similar, but the glabella is more cylindrical, not
widened below ; the tail is proportionally smaller, has the axis wider
and more convex, with fewer ribs, and there are but four distinct ribs on
each side. Fig. 8* is the tail of a young animal magnified.

Variations. — In some the axis is a little more prominent, in others a
greater or less depression of the glabella occurs, and apparently the
production forwards of the snout is not always in the same degree.
But these variations are within narrow limits, and our species never
seems to approach C. Blumenbachii in convexity, especially with regard

BRITISH FOSSILS. 3

to the glabella and caudal axis. The front is constantly produced, the
surface minutely scabrous, not covered with scattered tubercles, but this
last character occurs in some varieties of C. Blumenbachii, which is
more variable than we formerly believed.

Affinities. — It is distinguished from C. Blumenbachii, with which it
has always been confounded, and to which it is closely allied, by the
broad depressed form, narrow axis,* glabella not higher than the cheeks,
distant fulcrum, and wide depressed tail ; the produced recurved snout
also is a strong character. C. brevicapitata has the snout recurved, but it
is shorter ; the axis is prominent, and the fulcrum close to it ; the glabella
also is much shorter and smaller in front, and the whole form is elongate
and cylindrical. With the American species, as published by Green,
Hall, and Emmons, it does not need a close comparison : C. senaria is
attenuated posteriorly, and has a wide head, close fulcrum, and a small
tail, with the axis as broad as the sides : C. callicephala is distinguished
at once by the very short triangular glabella ; it has also a close fulcrum.
It is quite possible that hereafter forms may be found which will con-
nect this species with the more common C. Blumenbachii ; but at pre-
sent we do not know such forms, and it is necessary to point out the
obvious characters which distinguish them. Between C. Blumenbachii,
however, and the other British species, C. brevicapitata, specimens
intermediate in character, both as regards form and sculpture, liave
been discovered ; the present species, therefore, being founded on some-
what similar kinds of variation, must be received with caution.

History. — The early figures and descriptions of animals of this genus
had, of course, no reference to such minute differences as are now
deemed necessary for specific character ; however, there is one early
figure which certainly resembles more the depressed tail of our spe-
cies, with widely spreading and curved side ribs, than C. Blumenbachii ;
we mean that of Linnceus, "Stockholm Trans.," 1759, t. 1, f. 3.

Dalman describes, under C. Blumenbachii, three forms,t viz. : —

1. Var. tuberculata, in which he erroneously counts 12 segments to the
thorax, and reckons about seven ribs to the tail. Length, 2 inches to 2£.
Gottland and England ; the English specimen having the axis of the thorax
tuberculate on the sides, as in the next variety.

2. Var. Blumenbachii vera? a. tuberculosa, with 13 segments, and tail
with about eight ribs, the axis tuberculated on its sides ; the head, tail, and
lateral knobs of the axis closely scabrous; the dorsum (axis itself) smooth.
Length about an inch. Gottland.

* There is a variety of C. Blumenbachii, with narrower axis, found at the Hollies, near
Horderley, but the glabella and tail are normal, and the front not produced.

f " Et descriptiones auctorum, et specimina ad hac speciem relata, taiitas prcebent dis-
crepantias, ut fere credam diversas species sub hoc nomine esse commixtas, de qua re
tamen, ob speciminum inopiam, dijudicare nequeo." Dalman, Palaead., p. 35.

4 BRITISH FOSSILS.

3. Var. Blumenbachii vera, ft. pulchella, " undique punctis elevatis
sparsis," the axis hardly tuberculate at the sides ; small. Gottland.

Of these three forms the first is the most doubtful. Dalman has pro-
bably given a figure of it, bad in all points of detail, in his table 1, fig. 2.
This figure seems a little to resemble our species in the rather narrow
axis, and distant fulcrum, and there is no indication of bifid ribs to the
tail ; however, the snout is not produced at all, the axis of the tail is
also broad and convex, so that it probably is intended for the common
species. Of his var. pulchella (tab. 1, fig. 3), we have seen specimens
in the cabinet of Sir Roderick I. Murchison. They are dwarfs of C.
Blumenbachii, and, like it, have scattered tubercles, a large glabella,
and convex axis. But the description of var. 2 in so many respects
agrees with the subject of our plate, that we have adopted the term
tuberculosa as a specific name for it. The close minute scabrosity is
particularly alluded to by Dalman. Even if the identification be
incorrect, it will not involve any confusion of nomenclature. No
recognizable figure of this species appeared till the publication of the
" Silurian System," in which, at pi. 7, f. 5, a Burrington specimen is
figured, and in the description the knots on the axis are mentioned as
variable.

British Localities and Geological Position. — WENLOCK SHALE to
UPPER LUDLOW ROCKS. Upper Silurian beds, Underbarrow, near
Kendal, Westmoreland (Prof. Sedgwick). It abounds in nodules of the
Wenlock shale at Burrington, Shropshire, from whence thousands of
specimens have been distributed through collections. Small specimens
are plentiful at Usk, Monmouthshire, in Upper Ludlow Rock ; in
neither case associated with the more common C. Blumenbachii.

Foreign Distribution. — There is much reason to believe, as before
stated, that it occurs with the better known species in Gottland.

EXPLANATION OF PLATE VIII.

Fig. 1. Full-grown specimen from Burrington ; the head and tail a little bent down.
Fig. 1*. A specimen from the same locality, partially rolled up, but open sufficiently to
show the hypostome or mouth-piece attached to the rostral shield a.
Fig. 2. Extended specimen from the same locality.
Fig. 3. Dissected head ; k is the reflected front.

Fig. 4. Body segment separated, shows the nodular axis, and the distant fulcrum.
Fig. 5. Body segment seen in profile. It shows the depressed form of the body.
Fig. 6. Hypostome highlj' magnified.
Fig. 7. Magnified portion of the general surface.
Fig. 8. Young animal from Usk.
Fig. 8 a. Tail of ditto magnified.

J. W. SALTER.
June, 1849.

...... i

0 L E N U S MicRr^itr s S alter.

BRITISH FOSSILS.

DECADE II. PLATE IX.

OLENTTS MICRURUS.

[Genus OLENUS. DALMAN (in part). Sub-kingdom Articulate. Class Crustacea.
Order Entomostraca. Family Trilobitae.) Glabella narrowed anteriorly, lobed; eye
smooth, generally with a narrow prominent ridge connecting it with the upper part of the
glabella ; facial suture marginal in front, and cutting the posterior margin behind ; no
rostral shield ; hypostome . . . . ? pleurae 14, or fewer, pointed and recurved ; tail with
articulated axis and sides.]

[Sub-genus Olenm. Body rings 14 ; tail entire.]

DIAGNOSIS. O. ovatus postering attenuatus ; glabella genisque cequalibus ;
thorace segmentis 14, pleuris postremis axi angustioribus ; caudd transversa
Integra, apice truncato, axi l-annulato, lateribus unicostatis.

In the course of surveying the barren country south of Snowdon, Mr.
A. Selwyn, of the Geological Survey, discovered fine specimens of this
new Olenus. They were found only at two or three localities in the
lowest fossiliferous beds of the Silurian system, and may be considered,
therefore, as the oldest British trilobites ; they were associated with a
species of Eurypterus and a Lingula. The discovery is the more inte-
resting, as Olenus and Paradoxides are among the most ancient genera
of trilobites in the Silurian rocks of the Continent. Other British
species of the group have been described by Mr. John Phillips, from
the black shales of Malvern.

Description. — Length, one inch three-eighths ; width, seven-eighths.
General form broadly obovate, acuminate posteriorly ; the axis rather
prominent, and the sides flattened. Head more than twice as wide as
long, semicircular, with a narrow equal border, and produced at the
posterior angles into moderate diverging spines. Glabella reaching
very nearly to the front margin, bell-shaped, not very convex, but a
little swelled below, with a narrow neck lobe, and two lateral lobes.
Cheeks a little wider than the glabella. Eyes not large, forward, near
the glabella, and connected with it by a slight oblique prominence.
Eye line cutting the posterior margin far outwards. Pleurae 14, flattish,
increasing a little in width as far as the 6th segment, then shortened
gradually, so that the two last are scarcely wider than the tail ; each
marked by an oblique shallow furrow, deeper near the tips, which are
slightly recurved and produced into short spines. Axis narrowed pos-
[n. ix.] 2 i

2 BRITISH FOSSILS.

teriorly, not so wide as the pleurae in the anterior rings, but in the
hinder ones wider than the pleurae. Tail semicircular, truncate, the
axis convex with one rib above, and about equal in width to the sides,
which also have a single faint rib. Margin entire, slightly raised. But
four specimens have been found, and all more or less distorted.

Affinities. — From O. spinulosus, with which the head has considerable
resemblance, the entire truncate one-ribbed tail readily distinguishes it.
O, gibbosus, besides having a triangular, many-ribbed tail, has the gla-
bella not reaching nearly to the front margin, and the eye is placed at a
distance from the glabella nearly equal to the diameter of the latter.
In O. micrurus it is not above half the diameter distant. O. alatus, a
small species, named by Dr. Boeck, has the glabella extended forwards,
but it is very narrow and convex, and the eye is distant. The Olenus
gibbosus (Corda), which, in shape of tail, is very different from Swedish
specimens and Wahlenberg's description, differs from ours in the wide
and ribbed tail, as well as in the general shape, which is oval, not at-
tenuated ; besides other points. We know of no other species with
which it can be confounded.

British Localities and Geological Position. — LOWEST LLANDEILO
FLAGS (Lingula beds), Trawsfynydd, Merionethshire ; Cwm-y-Swm
mine, Dolgelly, ditto ; Marchllyn Mawr, near Llanberis, Caernarvon-
shire.

EXPLANATION OF PLATE IX.

Fig. 1. Olenus micrurus. Trawsfynydd.

Fig. 2. Same dissected, a, central lobe of the head,* including 5, the glabella, and c,
fixed cheeks; d, the mucronate wings; e, thorax segments, the obscure fulcral points
are at//; tail, g, with two-jointed axis, and single lateral furrow.

Fig. 3. Small specimen, Cwm-y-Swm mine, Dolgelly.

Note on the Genus.

The group of OlenidcE (Emmerich) includes genera which differ from each other in the
course of the facial suture ; in Paradoxides and Olenus its termination is on the posterior
margin, and the wings or free cheeks are produced into spines. In Pelttira (P. scara-
bceoides) and Triarthrus, it terminates in the posterior angle, or even a little above it. on
the external margin, and the wings are very small, and by no means produced into spines.

Paradoxides differs from Olenus in the large and clavate, not bell-shaped, glabella ; in
possessing 16 to 20 body rings, and a minute tail, with its axis only articulate.

Olenus is divisible into two sections, if these do not merit the name of genera. 1. The
group of true Olenus, to which our species belongs, having 14 body rings, and a tail with
entire margin. 2. O. spinulosus, having fewer, about 12 body rings, and a spinose or
laciniate tail ; for the latter species, the sub-generic name Parabolina, in allusion to the
shape of the glabella, might be appropriate.

June, 1849. J. W. SALTER.

* Corda has proposed to call all this " glabella," and to distinguish it into central and
lateral lobes.

I

A M PYX Tti-Drs . }finrln.<,-i.

BRITISH FOSSILS,

DECADE II. PLATE X.

AMPYX NT7DUS.

[Genus .AMPYX. DAYMAN. (Sub-kingdom Articulata. Class Crustacea. Order
Entomostraca. Family Trilobitae.) Glabella tumid, armed with a frontal spine ; head
with simple, unexpanded margins ; angles spinous ; no facial suture ; no eyes ; body rings
5 or 6 ; tail entire-margined, margin deflected ; hypostome ?]

DIAGNOSIS. A.latus; capite semicircular i, spina frontali brev i ; angulis
longe-spinosis ; glabella vix producta, lateribus bilobatis ; thorace articulis 6 ;
caudd lateribus 8 — 9 sulcatis.

SYNONYMS. Trinucleus nudus, MURCHISON (1839), "Sil. Syst.," p. 660,
pi. 23, f. 5.

Description. — General outline broadly oval ; body much depressed ;
the general axis, consisting of glabella, axis of thorax, and axis of tail,
forming a lanceolate, convex, central elevation, narrowing posteriorly.
Head, thorax, and tail of equal length. The first is rounded, with
the outline, in front, slightly prominent, and the whole less than a
semicircle ; the last is slightly triangular. Glabella somewhat claviform,
rounded and convex in front, narrowing behind the middle, and slightly
widening out at its junction with the neck furrow ; it is marked at each
side by two or three indistinct furrows, and, towards its centre, by two
very oblique furrows, which form small elliptical elevated spaces, one
on each side, bounded by rounded and curved folds, below the level of
the rest of the glabella, and appearing as if distinct from it. From the
front of the glabella projects a slender subulate spine, which, in all
examples hitherto met with, is rather less than the -length of the head :
it is not continued as a keel on the central surface of the glabella.
The neck furrow is well marked, and the neck fold elevated. The
cheeks are broad, depressed obliquely in their centres; the depres-
sion proceeds from near the upper extremity of the glabella lobes,
and continues obliquely outwards, with an obscure curve towards, but
not touching the margin. Between the depression and the hinder por-
tion of the glabella the cheek is gently tumid, and likewise between the
depression and the outer margin. The neck furrow runs straight and

[II. X.] 2 K

2 BRITISH FOSSILS.

close to the hinder margin of each cheek, leaving the edge elevated as
a thickened and very narrow rim ; and then, at the angles of the head,
making a slight curve, runs into and furrows the base of a long spine.
This spine is of a subulate form, and projects backwards in a curved
manner from the head angles, and at a distance equal to rather less than
the breadth of the cheek, bends backwards and straight to more than the
tail's length beyond the posterior extremity. No trace of a facial suture
has been observed in any of the specimens as yet discovered.

The axis of the thorax is convex, and nearly equal in breadth
throughout, very slightly narrowing at its junction with the tail. Its
width is about two-thirds of that of the pleurae. Each joint of the axis
is deeply furrowed centrally, elevated anteriorly and posteriorly, the
elevations of the proximate joints uniting to form a strong convex,
somewhat curved, rounded rib, running across the axis, and terminated
at each side by a conspicuous tubercle. Six such ribs mark as many
thoracic articulations. The axis is separated from the pleura? on each
side by a deep but narrow groove. The pleurae are straight, narrow,
and depressed, tumid along their lengths on each side of a conspicuous
deep oblique furrow ; extremities obliquely truncated, slightly turned
backwards. The surface of the tumid portions of the thorax, and also
of the more convex parts of head and tail, are minutely granulated.

Tail triangular, with the sides slightly curved outwardly. Its axis
prominent, gently tapering for nearly two-thirds of its length, then
becoming parallel-sided, and ending obtusely at the termination of the
tail. Nine ribs like those crossing the thoracic axis, but smaller and
without marginal tubercles, cross the tapering portion of the axis ; the
remainder is ringed by numerous minute ribs. The axis of the tail is
divided by a deeply-impressed furrow from the sides, which are gently
convex, and grooved by eight strongly-marked lateral furrows, oblique,
and curved slightly backward ; the interspaces are tumid. The upper-
most furrow commences at the junction of the tail with the body, and
proceeds obliquely onwards to the margin, so as to leave a narrow,
lanceolate, triangular space in front of it. The distance between its
marginal extremity and that of the next furrow is greater than the dis-
tance between the extremities of any of the other furrows. The last
and shortest furrow originates just above the termination of the tapering
part of the tail-axis, and between it and the extremity is a smooth and
slightly tumid triangular space. The margin of the tail has an elevated
rim, the deflected portion of which is striated.

Young specimens have the same number of thoracic joints with adult
examples, and do not appear to differ materially in any respect.

The length, exclusive of the frontal spine, of the largest specimen ex-
amined, was one inch and three twelfths. The frontal spine measured

BRITISH FOSSILS. 3

nearly five -twelfths. The breadth of the thorax was one inch. The
length of a cheek-spine one inch and five-twelfths.

Affinities. — Its nearest ally is the Ampyx mammillatus of Sars (A,
Austinii of Portlock), which it resembles in general outline, in form of
head, and features of glabella, and also in the number of thoracic rings.
The tail of Ampyx mammillatus is, however, very differently shaped, and
has only one lateral furrow on each side, and its axis is, in great part,
smooth. There are also very material differences in the structure of
the cheeks and pleurae. Ampyx nasutus (Dalman), is described as
having six articulations, but has a very prominent glabella protruding
much beyond the cheeks, and a tail represented as smooth at the sides.
The figure given by Dalman, however, so closely resembles the Ampyx
rostratus of Sars (A. Sarsii, Portlock), that I am inclined to think that
the fold on each side of the tail above the single lateral furrow was
mistaken for a joint of the thorax, for in all the other species of Ampyx
there are only five thoracic segments with the peculiar triangular outline
of the head, which is so shaped in consequence of the great projection of
the front of the glabella beyond the cheeks. These characters we see
combined in Ampyx rostratus, Ampyx Portlockii (Barrande), Ampyx
bokemicus of Hawle and Corda, and my Ampyx parvulus. The Ampyx
Brucltneri of Boll has the same form of head, but the body of that
species is unknown. If, in the end, all the five-ringed species should
prove to have long heads, and those with six thoracic segments to have
short and rounded ones, the latter section may be conveniently distin-
guished from the former as a subgenus, under the name of Brachampyx.

History. — This curious trilobite was discovered by Sir Roderick
Murchison, and figured by him in the Silurian System as a species of
Trinucleus^ of which genus he considered it a member, supposing the
border of the head to be lost, and regarded it as allied to his Trinucleus
fimlriatus, but as differing in the number of ribs on the tail. In 1845, a
number of specimens were found in the original locality at Builth by
Sir Henry de la Beche and myself, in more perfect condition than those
first figured, and they proved, without question, to belong to the genus
Ampyx. On examination of the original specimens figured in the Silu-
rian System, I found that they also exhibited traces of the frontal spine.
The true generic position of this trilobite was afterwards indicated in a
note to the Ray edition of " Burmeister's Essay ;" that author had re-
garded it as a mutilated example of Trinucleus fimlriatus.

British Localities and Geological Ranges. — Hitherto this Ampyx has
occurred only in the LLANDEILO FLAGS of Carneddau Hill, near Builth,
Radnorshire, South Wales.

BIJITISH FOSSILS,

EXPLANATION OF PLATE X.

Fig. 1. Figure of the entire trilobite, slightly restored, from the Builth specimen.
All the parts are shown in specimens in the collection of the Geological Survey.

Fig. 1*. Dissection of the species. Lines as if of a facial suture are seen ou the glabella,
but they do not seem to indicate any true separation of parts.

Fig. 2. An individual still younger.

Fig. 3. A small specimen, showing the constancy of its characters at an early stage.

Fig. 4. Granulation of the head.

Fig. 5. Granulation as seen towards the extremity of one of the pleurae.

Fig. 6. Lineation of deflected surface of tail margin.

Note on the British Species of Ampyx.

The genus Ampyx was first recognized as British by Lieut.- Col on el Portlock, R.E., who
described and figured two species, Ampyx Austinii, identical with A. mammillatus (Sars),
and Ampyx Sarsii, identical with A. roslratus (Sars), and probably with A. nasuttts (Dai-
man). Both these forms were discovered during the researches of the Ordnance Geolo-
gical Survey in Ireland, the former in the Silurian slates of Tyrone, and the latter in
those of Newtown, near Waterford. Recent researches have led to the conclusion that
the strata in which these fossils were found are members of the lower (Llandeilo or
Bala) division of the Silurian rocks.

In Great Britain neither of these species of Ampyx have, as yet, occurred. The only
species described as British, besides that now figured, is my Ampijx parvulus, from the
Lower Ludlow of Vennal Hill (Mem. Geol. Surv., vol. ii. pt. 2, p. 350, pi. x.) There
appears, however, to exist a third species in the Rhiwlas limestone, near Bala ; one dis-
tinct from any as yet described, but of which only heads and tails have been found. The
largest head is half an inch in length, exclusive of the spine. It is nearly allied to A. ros-
tratus, but differs in having much smaller cheeks in proportion to the glabella, whioh is
even more produced than in the rostratus, and exceedingly tumid. The cheeks in the
species to which I have compared it are beyond the middle of the glabella ; in the Rhiw-
las form never so far as that part. The neck lobe of the latter is narrow, and the tail,
though similar in sculpture, much shorter and wider. The proportions of the cheeks and
glabella remind us of A. Bruckneri (Boll in Dunker and Von Meyer's Palseontogra-
phica, 1st Band, 11 lief., t. xvii., f. 8), but that species has a carinated glabella, and very
broad neck lobe. Ampyx Poitlockii (Barrande), is said to have the glabella much less
elongated than A. nasntus, and therefore cannot be the Rhiwlas form. A. bohemiciis
(Hawle and Corda, t. 3, f. 19), comes nearer, but is represented as having a much wider
glabella and a proportionately much smaller tail, with no traces of rings on its axis. I
propose to name the Rhiwlas species, Ampyx tunridus.

Ampyx baccatus, of Portlock, does not belong to this genus.

E. FORBES.
July, 1849.

LIST OF GEOLOGICAL MAPS AND SECTIONS,

PUBLISHED BY MESSBS. LONGMAN AND Co., FOR HER MAJESTY'S STATIONERY OFFIC

[THESE Maps consist of the Maps of the Ordnance Survey, Geologically Surveyed and Coloured by
Geological Survey of Great Britain, by the Authority of Her Majesty's Government, under the Superintend^
of Sir HENRY DE LA BECHE, Director-General of the Geological Surveys of the United Kingdom. The vari
Formations are distinctly traced and coloured in all their Geological Subdivisions.]

GREAT BRITAIN The Counties of which the Geological Survey is completed, are—

CORNWALL, including Sheets 24, 25, 26, 29, 30. 31, 32, and 33. Sheets, it 5s. I The Geology of these two Com-

{ is amply illustrated by Sir
DEVONSHIRE, including Sheets 20, 21, 22, 23, 24, 25, 26, 27, and 29. Sheets, 2Z. 1 Is. [ De la Heche's Report. 8vo.

GLAMORGANSHIRE, including Sheets 20, 36, 37, 41, and 42 (SE. & SW.). Sheets, 2/. { H££°" mu^trat^hu County.
MONMOUTHSHIRE, including Sheets 35, 36, 42 (SE. & NE.), & 43 (SW.). Sheets, \l. 1 Is. { "^"u

1 9. [Half of Somerset, and part of West Wilts.] 1 1 s. 6d.

20. [West Somerset, and part of Soutli Glamorgan.] 5s. Gd.

21. [SW. Somerset, NE. Devon, and part of West Dorset.] 10s.

22. [Part of SE. Devon.] 7s.

23. [Devon between Torbay and Star Point.] 3s.

24. [Part of South Devon and Cornwall.] 3s. 6d.

25. [SW. Devon and East Cornwall.] 10s.

26. [West Devon and NE. Cornwall.] 6s.

27. [Devonian Rocks.] 3s. 6rf.

28. [Lundy Island.] 2s. 6d.

29. [The North of Cornwall.] 2s. &d.

30. [Part of Corn wall.] 7s. 6rf.

31. [Part of Cornwall.] 7s. 6d.

32. [Part of Cornwall.] 3s.

35! [Western Gloucester, the SE. of Monmouth, part of North | 57 NE*" [Part of Cardiganshire.] 2s. 6d.
Somerset and West Wilts.] 10s. i 57 SW. [Part of Cardiganshire.] Is. 6d

41. [Most of Carmarthen, parts of North Glamorgan, Soi

Cardigan, and East Pembroke.] 8s.

42 NW. [West Brecknock and part of East Carmarthen.] 2s
42 NE. [Part of East Brecknock and West Hereford.] 2s.
42 SW. [The SW. of Brecknock, part of North Glamorgan a

East Carmarthen.] 2s. 6d.

42 SE. [Completes the NE. of the Glamorgan and Monmoi

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43 NW [The Old Red Sandstone, and part of the Silur

Strata of Woolhope.] 2s.
43 NE. [Completes the Silurian District of Woolhope, with

Malvem Country as far North as the Wych.] 2s. 6d.
43 SW. [The West of" Dean Forest Coal Field.] 3s.
43 SE. [The greater part of Dean Forest Coal Field, &c.] I
57 NW. [Part of Cardiganshire, on the Coast.] Is.

36. [The greater part of Glamorgan on the West, and Monmouth

on the East.] 13s.

37. [West Glamorgan and South Carmarthen.] 8s.

38. [South Pembroke.] -Is.

39. [Small's Light, Pembroke ; Bishop and his Clerks.] 2s. 6d.

40. [North Pembroke and West Carmarthen.] 8s.

SE. [Part of Cardiganshire.] 2s.
[Part of the Coast of Cardiganshire and North Pembrc

shire.] 2s. 6d.

59 SE. [The North of Cardiganshire ; part of the West of M

gomery and the South of Merionethshire.] 3s.\
59 SW. Sea. (No Geological Colouring.) 6<f.

INDEX to the COLOURS and SIGNS employed in the Geological Survey of Great Britain for South Wes
England and Wales. 8s.

HORIZONTAL SECTIONS,

(Constructed by the Geological Survey of Great Britain,') illustrative of the Survey's Geological Map.

These Sections are drawn to a scale of six inches to a mile, horizontally and vertically, and describe in detail the Geology ol :

Country over which they are drawn. Descriptions are engraved on each plate, thus rendering each Section a concise Report ol !

district it traverses. The size of each plate is 3 ft. 3 in. by 2 ft. 3 in. They are engraved on Copper by Mr. Lowry, and colour i
accordance with the Maps. Sheets 1 to 17, price 7s. each.

VERTICAL SECTIONS,

Illustrative of the Horizontal Sections and Maps of the Geological Survey of Great Britain.

istrate such details as
,..v, the Thickness of each
and Amount of Ironstom i

I RE LAN D — MAP OF WICKLOW, 7s. 6d. MAP OF CARLOW, 7s. Gd. MAP OF KILDARE, 7s. i
HORIZONTAL SECTIONS, &.C.

No 1. From the Coal Measures of Queen's County to the Rock of Arklow, County Wicklow. >
No. 2. From near Dunlavin, across the summit of Lugnaquilla to the Sea near Johnstown.
No. 3. First. From Glencree across Sugar-loaf Hill.

Secotid. From Lough Tay to near Five Mile Point. I 7s. eacl i

Third. From near Baltinglass to Lugnaquilla.

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PLAN and SECTIONS of the OVOCA MINES, County Wicklow.

BOOKS Published under the Superintendence of the Geological Survey.

REPORT on CORNWALL, DEVON, and WEST SOMERSET. By Sir H. T. DE LA BECHE, F.R.S. ,

8vo. 14s.
FIGURES and DESCRIPTIONS of the PALAEOZOIC FOSSILS in the above Counties. By PROFE <

PHILLIPS. 8vo. 9s.

THE MEMOIRS of the GEOLOGICAL SURVEY of GREAT BRITAIN, and of the MUSEU R

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