a

UNIVERSITY OF CALIFORNIA
AT LOS ANGELES

The RALPH D. REED LIBRARY

o

DEPARTMENT OF GEOLOGY

UNIVERSITY OF CALIFORNIA

LOS ANGELES, CALIF.

MEMOIRS

GEOLOGICAL SUKYEY

THE UNITED KINGDOM.

jfigttrrs null

ILLUSTRATIVE OF

BRITISH ORGANIC REMAINS,

MONOGRAPH I.

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

LONDON:

PRINTED FOE HER MAJESTY'S STATIONERY OFFICE:

PUBLISHED BY

LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS
1859.

NOTICE.

The SESSION of the GOVERNMENT SCHOOL OF MINES and
of SCIENCE applied to the ARTS commences early in October
in each year, during which the following Courses of
Lectures are delivered : —

Chemistry, with special reference to "j

its applications in the Arts and > A. W. Hofmann,LL.D., F.R.S.

Manufactures - - )

General Natural History - - T. H. Huxley, F.R.S.

Physics - - G. G. Stokes, M.A., F.R.S.

Applied Mechanics - Robert Willis, M.A., F.R.S.

Metallurgy - - John Percy, M.D., F.R.S.

Geology - - A. C. Ramsay, F.R.S.

Mining - -j f Warington W. Smyth, M.A.,

Mineralogy

- •) f W armgl

.} ' ~\ F.R.S.

The Chemical Laboratory, under the direction of
Dr. Hofmann, and the Metallurgical Laboratory, under
the direction of Dr. Percy, are open for the instruction of
Students.

A Prospectus and Information may be obtained on
application to

TRENHAM REEKS, Registrar.

Jermyn Street, London. S. W.

MEMOIRS

GEOLOGICAL SUBYEY

THE UNITED KINGDOM.

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ILLUSTRATIVE OP

BRITISH ORGANIC REMAINS.

MONOGRAPH I.

PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HER MAJESTY S TREASCKT.

LONDON:

PRINTED FOR HER MAJESTY'S STATIONERY OFFICE:

PUBLISHED BY

LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS.
1859.

Gsoicgy Dept

NOTICE.

THE accompanying Monograph, by Professor Huxley and Mr. Salter,
shows the advantage accruing to geological science from the com-
bined efforts of the Naturalist and the Paleontologist.

Having devoted many years of my life to the establishment of
the true order of those strata which are characterised by the genus
Pterygotus, i.e. the Upper Silurian Rocks of Britain and Russia, and
the Lower Old Red Sandstone of Scotland, it is peculiarly gratifying
to me to announce the issue of a work which, whilst it throws
fresh light on the organic remains of those deposits, and must be
valued by all naturalists, will at the same time sustain the useful-
ness of the study of fossil remains, in developing the true geological
structure of the British Isles.

The figures and descriptions of British Organic Remains having
been hitherto, in great measure, confined to the illustration of
isolated genera and species, it was found convenient to publish
them, at intervals, in fasciculi of Ten, under the term of Decades.
That title is, however, obviously inapplicable to Memoirs like the
present, and to other Monographs containing a variable number
of plates, which are in preparation.

RODEEICK I. MURCHISOX,

December 31, 1858. Director-General*

[1.] A 2

ft

* "S55815

BRITISH FOSSILS.

MONOGRAPH THE FIRST.

PART I. — On the ANATOMY and AFFINITIES of the Genus PTERY-
GOTUS. — By THOMAS H. HUXLEY, F.R.S., Professor of Natural
History, Government School of Mines.

THE genus Pterygotus was established by Professor Agassi z, in the
following note appended to page xix. of his well-known work, the
" Monographic des Poissons Fossiles du Vieux Gres Rouge" (1844) : —

" The Plate A, accompanying this monograph, represents many
well preserved fragments of one of those gigantic Crustacea of the
Old Red, collected by Mr. Webster in the neighbourhood of Bal-
ruddery, in Scotland. Deceived by the scaly aspect of a portion of
the carapace, I at first believed that this might be the type of a
peculiar genus of fishes, and to that class I referred Pterygotus, in
my enumeration of the fossil fishes of the Silurian system, published
in Murchison's great work. This genus, founded upon very imper-
fect fragments from the Ludlow rocks, is now well known, from the
investigations which I have been enabled to make of a new species
from the Old Red, discovered by Lyell, in Forfarshire, and of which
Mr. Webster has found more characteristic remains at Balruddery.
The specimens collected by Lyell are those large scutes, of which I
have spoken in my ' Recherches/ vol. i. p. 26, and which, in the
absence of the means of rigorous determination, have been seriously
taken for the remains of superhuman beings.

" Dr. Buckland and I, on examining them carefully, convinced our-
selves that they must be the carapaces of Crustacea ; but it was only
in 1840 that I obtained direct proof that such was the case. In
fact, among the specimens collected and communicated to me at that
time by Mr. Webster, are fragments of carapaces, segments of the
tail, the natatory palettes with which the extremity of the latter
was provided, legs, and chelae. These remains remove all doubt as
to the zoological position of the fossil. It is a crustacean of colossal
size, having a carapace of more than a foot and a half in width, and
a tail about a foot wide. The dimensions of the cephalothorax,

6 BKITISH FOSSILS.

represented in the right-hand figure of the second row, Plate A,*
forbid its arrangement among the Decapoda, notwithstanding the
form of the chela figured in the middle of the lower series of the
same plate.f I am rather inclined to believe that this singular
animal will become the type of a family, intermediate between the
Trilobites and the Entomostraca, in which perhaps the Eurypteri
and the Eidothece will some day be included. The carapace is
ornamented throughout with a squamose sculpture, which confers
upon its surface the aspect of a fish's cuirasse ; in the middle it
presents an impression like that of a lance-head, corresponding,
without doubt, to the gastric and cardiac regions of ordinary Crus-
tacea. The divisions of the chela are provided with large obtuse
teeth ; the longer point of these levers is strongly arcuated. The
arm which carried the chelaj (figured on the left in the lower series)
is very large ; the articulations which immediately precede the
pincer are short, and wider than they are long. The ordinary legs
(figured on the left in the middle series §) are simple, and end in a
point ; the segments to which they are attached are sensibly longer
than they are wide.

" The segments of the tail,)] (represented in the right-hand figure of
the upper series,) reduced to half their natural size, are broad plates,
provided with articular processes at their superior extremities,
Lastly, the natatory palettes of the tail (the two figures at the
superior left-hand and inferior right-hand corners^]") are rounded
plates, fringed along their edges, and scaly on the surface, like the
carapace. This curious fossil does not seem to be very rare in the
Old Red of Scotland. I have conferred upon this species the name
of Pterygotus anglicus, which at once suggests its origin and the
singular view which was once entertained as to its nature/'

Although the parts figured by M. Agassiz have, as I have taken
occasion to point out in successive notes, in no single case the nature
attributed to them, his sagacious indication of the affinities of
Pterygotus deserves thankful recognition.

The views of Professor Agassiz respecting the affinities of
Pterygotus are adopted and expressed still more strongly by M. von

* This is in fact the epistoma.

f The part thus figured is one of the antennae.

| The figure here referred to represents a part of the palp of the ectognath, which has
nothing to do with the chela.

§ This is an endognath with its palp ; no segment is represented in the figure.

|| The figure represents one of the most anterior segments of the body.

«j[ The part shown in the superior left-hand figure is part of the basal joint of an ecto-
gnath. The inferior right-hand figure represents the terminal joint of the palp of the
same organ.

BRITISH FOSSILS. 7

Eichwald, in his Memoir on the Grauwacke of Livonia and Esthoma.*
" It appears at first sight," says he, " that this (Pterygotus) was a
colossal Eurypterus, at least the genera are very closely allied/'
M. von Eichwald differs from Agassiz only in considering the latter's
" caudal segment " to have been thoracic. His specimen, which he
ascribes to P. anglicus, was found in the Limestones of Kootsikiille.
In the Annals and Magazine of Natural History for 1849/series 2,
vol. iv. pp. 393, 394, Professor M'Coy gives an account of the
remains of a new species of Pterygotus, P. leptocheles. In his pre-
paratory remarks, Professor M'Coy erroneously states that Agassiz
has " in his work on the Fishes of the Old Red Sandstone referred it
(Pterygotus) to the Entomostraca, without indicating any particular
division/' The fact being, as is proved by the quotation just given,
that he does not consider Pterygotus to be entomostracan at all, but
to be intermediate between " Trilobites and Entomostraca."

Following Agassiz and Eichwald, Professor M'Coy indicates the
close relations which obtain between Pterygotus and Eurypterus ;
but he unites Pterygotus, Eurypterus, and Bellinurus, and makes
of them a family of the Pcecilopoda. Professor M'Coy considers
that he has found evidence of the existence of more than one
pair of didactyle feet.

Professor M'Coy's views are further expressed in the restored
figures of Pterygotus, which he has furnished to the fifth edition of
Sir Chas. Ly ell's " Manual," (1855,) and in the following passage
of that work (p. 420):—

" The carapace of this huge crustacean, which must have rivalled,
if not exceeded in size, the largest crab, is furnished at its hind
part with two short prongs, and has two large eyes near the
middle, much like those of the Eurypterus found in the coal-
formation of Glasgow. The body consists of ten or eleven
moveable rings (the exact number is not ascertained), and was
terminated by an oval pointed tail. The whole surface is covered
by the scale-like markings before mentioned as ornamenting the
head. Professor M'Coy, to whom I owe these notes on the
general structure, has kindly furnished me with a restoration of
the entire animal (fig. 543), which he believes to be closely
allied to the great Eurypterus before mentioned, if not of the
very same genus, and moreover of the same family as the living
king crab or Limulus."

The restorations exhibit, in figs. 542, 543, 544, the chelae fitted
on to the ends of the mutilated ectognathary palp, in accordance

* Die Grauwacke Schichten von Liv-und Esth-land, von Ed. von Eichwald. Bulletin
de la Socic-te Imperiale des Naturalistes de Moscou.

8 BRITISH FOSSILS.

with Agassiz's idea of their position ; while, in fig. 543, the
epistoma is represented as the carapace, and a transversely
elongated eye is made to appear on either side of its median lobe,
about midway between the 'middle line and the margin! The
chelate appendages are made to arise from behind this supposed
carapace, and are succeeded by two or three pairs of articulated
appendages. In short, wherever Professor M'Coy departs from
M. Agassiz's conception of the structure of Pterygotus, the altera-
tion is not an improvement.

In 1852 Mr. Salter published a " Description of the Pterygotus
problematicus" in the "Quarterly Journal of the Geological Society,"
in which the following passage occurs : —

" It is probable that there are numerous species of the genus in
the old rocks. Fragments, with the characteristic markings, occur
in Upper Silurian shale at Gaspe', Lower Canada ; and portions
of the limbs of a Bohemian species have been figured by the
late M. Corda as the feet of Brontes, a genus of Trilobites."

Mr. Salter expresses his concurrence in the systematic views of
Professor M'Coy.

The Report of the British Association for 1855, " Transactions of
the Sections," (pp. 89-91), contains the abstract of a paper by Mr.
D. Page, " On the Pterygotus and Pterygotus Beds of Great
Britain." The following passages show what views were then
entertained by Mr. Page with respect to the structure of these
animals : —

" The Pterygotus, of which there appeared to be three distinct
species, — the gigantic problematicus, the anglicus, and the punc-
tatus, — was altogether different in its general structure' from any
crustacean living or extinct. The portions chiefly found (and of
these capital specimens are in the collections of Lord Kinnaird,
the Watt Institution, Dundee, &c., all originally from Balruddery,)
were the frontal cephalic shield, the posterior cephalic or thoracic
shield, with its lunar-like epimera, the abdominal segments, gene-
rally from seven to eleven in number, the huge prehensile claws
with their curious denticulated edges attached to limbs of great
length, the shorter swimming limbs with their paddle-like ap-
pendage, and several semi-oval detached plates which evidently
belonged to the breast or under side of the animal. Putting all
these portions in place as nearly as could be determined, we had
a huge lobster-like crustacean, but only lobster-like in general
contour, for in its true generic relations it belonged to no existing
family of the order. Partly phyllopod and partly psecilopod, in
its abdominal segmentation macrourous, and in its thoracic appa-

BRITISH FOSSILS. 9

ratus resembling the existing Limulus. The Pterygotus could
be classed with no living family, and was in aspect more like the
larvae than the adult forms, of any Crustacea with which we are
acquainted. This peculiarity, indeed, ran throughout the whole of
the Crustacea, (and there were several new forms he would notice
on another occasion,) which had hitherto been found in this
geological horizon, — a horizon that would yet be found to be
marked peculiarly by its strange Crustacea. From the portions he
now exhibited to the section, the members eould perceive at a
glance that the restoration by Professor M'Coy was altogether
erroneous, and bore scarcely any resemblance to what the crea-
ture must have been when alive, and acting the part of a
scavenger along the muddy shores of the Old Red Sandstone seas.
The figures on the walls (Mr. Page here exhibited what he con-
ceived to be a near approach to a complete restoration) would
afford some idea of the general features of the animal, which he
had found of all sizes from ten or twelve inches up to full five or
six feet in length. Such was the Pterygotus, and looking at its
complex structure, as well as the similar structure of other Crus-
tacea of the period, there could be no doubt that no existing
classification of the order embraced them in its subdivisions. The
fact was, that the existing Crustacea were by no means well
worked out as a group, and the discovery of these strange fossil
forms rendered the study still less perfect."

The comparative anatomist acquainted with the labours of Milne
Edwards, Dana, Bell, Baird, Schaeffer, Darwin, and a host of other
workers, will hardly be disposed to agree with the opinion expressed
in the commencement of Mr. Page's last paragraph, though doubt-
less a good deal remains to be done. In Mr. Page's reference of the
Pterygoti to a distinct group, he has, as we have seen, been antici-
pated, and his restoration of their structure is hardly more fortunate
than that of his predecessors. His " posterior cephalic or thoracic
shield " is the epistoma, and has a wholly different place from that
assigned to it ; like Agassiz and M'Coy he places the chelae at the
end of the ectognathary palps, and considers them to terminate
thoracic appendages.

Mr. Page's paper was read before the British Association at its
meeting in 1855. In November of the same year Mr. Salter com-
municated a paper to the Geological Society " On some new
Crustacea from the Uppermost Silurian Rocks," to which I added a
note on the structure and affinities of Himantopterus.

Mr. Salter points out the differences between Himantopterus

10 BRITISH FOSSILS.

and Eurypterus, and establishes six species of the former genus,
whose structure and affinities are discussed in my own note.
Subsequent investigation has confirmed the views therein taken of
the carapace, its eyes, the chelate antennae, the swimming feet, the
general structure of the body, and the absence of abdominal or
thoracic appendages ; nor has it, as yet, been absolutely proved that
there were more than three pairs of cephalic appendages ; but the
basal joints of the ectognaths were mistaken for mandibles, and
their connexion with the long palp-like swimming foot was not
observed. Neither the epistoma nor the metastoma (the latter is
figured in the restoration as a "scale-like appendage") were
determined. In inquiring into the affinities of Himantopterus, I
compared it successively, with the Phyllopoda, the Pcecilopoda, the
Copepoda, and the grounds on which I objected to refer it to either
of these orders seem to me still, substantially, to hold good. I then
proceeded to compare it with the Cumoid Crustacea, with certain
Stomapoda, and with the embryonic forms of the higher Crustacea,
and I concluded by expressing the opinion, that " the nearest
approach to Himantopterus which could be constructed out of the
elements afforded by existing Crustacea, would be produced by
superinducing upon the general form of a Cumoid crustacean, such
a modification of the appendages as we find among the Zoceiform
Macruran larvse."*

In his " Advanced Text-Book of Geology," p. 135 (1856.) Mr. Page
gives a figure of one of the specimens on which Himantopterus
was based, and provisionally admits that genus, adopting the
" Cumoid " affinities which I had suggested. He considers that those
palaeozoic Crustacea and their allies exhibit, "as it were, an interfu-
sion of phyllopod, psecilopod, and decapod — of brachyurous, macrou-
rous, and xiphosurous forms," and figures and names " Slimonia "
and <£ Stylonurus" which he considers to be new genera, but which
are not as yet proved to be other than species of Eurypterus and
Pterygotus.

Mr. Salter communicated to the meeting of the British Association,
in 1856, a paper " On the great Pterygotus (seraphim) of Scotland,
and other Species/' containing his opinion as to the identity of the
genera Himantopterus^ and Pterygotus, and some of the farther
anatomical facts which had at that time been elucidated.

* Mr. Salter has misunderstood me, when he says at the end of his memoir (I.e.) that I
consider Himantopterus to be " one of the Stomapoda." On the contrary, I have always
heen prepared to admit the ordinal distinctness of the Eurypterida.

f The name Himantopterus could in no case have been retained, as it has been already
used for a genus of lepidopterous insects.

BRITISH FOSSILS. H

And, lastly, I stated the results of the same inquiries still more
fully in my " Lectures on General Natural History/' published in
the Medical Times and Gazette for 1857.

The evidence upon which the following attempt to give a con-
nected account of the structure of Pterygotus is based, is both
positive and negative. Numerous specimens testify to the existence
of certain characteristically formed parts, and to the arrangement 01
these in a definite order in the body of the animal, so that its
general configuration may be very confidently restored. On the
other hand, the large number of fragments of many species of
Pterygotus which have been inspected, without revealing anything
new, leads me to entertain a strong impression that no structures
of any very great importance remain to be discovered.

With regard to the nature of the positive evidence, I may
premise that of the fifteen distinguishable species of the genus,
the remains of only five, viz., anglicus, acuminatus, punctatus,
perornatus, and bilobus have yielded facts of capital importance in
a structural point of view ; I shall, therefore, confine myself to
these species, referring the reader to the systematic portion of this
monograph for information respecting the rest, and indeed for all
details of no anatomical importance concerning even these. .

Of the species named, the only entire specimens yet discovered
belong to P. bilobus, but the large size and comparatively perfect
condition of the detached parts of P. anglicus, added to the fact
that the genus was originally founded on this species, render it
convenient to commence with a description of them.

1. The Carapace. — In Lord Kinnaird's collection there is a large
flattened plate, figured in Plate III. fig. 1, which appears to have
possessed a trapezoidal form when perfect, but is at present very
irregular (though by no means distorted), one of its angles and a
considerable portion of the margin of the longest side having been
broken away. The shortest or anterior side is very slightly convex,
the opposite and parallel longest side is a little concave; that
lateral margin which is entire is nearly straight, but is rounded off
where it joins the posterior edge. The surface of the fossil is slightly
concave, and exhibits neither sculpture nor distinct granulation, but
it is marked by a great number of sinuous elevations and depres-
sions. At the outer extremities of the anterior edge are two large
and deep depressions of an oval form, having their long axes directed
obliquely forwards and inwards.

The surface of each concavity presents a great number of minute,
but regular and close-set depressions (Figs. 1 a, 1 6), which appear

12 BRITISH FOSSILS.

quite distinct when viewed from a little distance, but whose form
is by no means easily denned on closer inspection. On the inner
side of one of these concavities a broad longitudinal depression
traverses the surface for some distance. Primd facie, one would be
inclined to take this great plate for a carapace, and the lateral,
peculiarly sculptured, concavities for the vestiges of eyes ; and any
doubt on the subject will be at once removed on comparing it with
the carapaces ofPterygotus Ulobus or perornatus (Plate I. figs. 1, 13) ;
but it is somewhat difficult to decide whether the fossil is merely
the impression of the dorsal surface of a carapace, or whether we
really see the inner face of the carapace itself. The absence of the
characteristic sculpture is not conclusive against the former deter-
mination, as, with the exception of its anterior edge, the dorsal
surface of the carapace of P. perornatus is equally devoid of
ornament.

However this may be, the long margin must clearly be posterior,
and the entire lateral edge, the right, while the piece broken off
is the left posterior lateral angle. If a line be drawn so as to con-
tinue the direction of the anterior part of the left edge backwards
until it meets the line of the posterior edge, it will represent the
general course of the broken margin, and the carapace will then be
found to have had a trapezoidal form, the posterior edge being
nearly twice as long as the anterior, and the antero-posterior
diameter being about equal to the length of the anterior margin.
The right lateral edge is more or less crushed and distorted.

This is the only .known example* of the carapace of P. anglicus ;
the fossil described as such by Professor Agassiz must therefore
have a totally different nature.

2. The Epistoma. — It is this remarkable structure which is figured
in a state of greater or less perfection in Plate III. figs. 2, 7.

The most perfect specimens (figs. 2, 5,) reveal a broad plate
having one edge nearly straight, but presenting a slight median
emargination, while the opposite edge inclines from the middle line
on each side outwards towards the straight margin, which it would,
if continued, cut at a considerable angle.

In the middle line a slight longitudinal depression passes along
the face of the plate for a short distance, from the straight margin
towards the convex one, and then divides into two diverging grooves.

From the extremities of these, two others, slightly convex
towards one another and the median line, are continued as far as
the convex edge, and thus the plate becomes divided into three

* Mr. Salter informs me that there are two more in Lord Kinnaird's collection, which
I have not seen.

BRITISH FOSSILS. 13

regions, — a narrow " median lobe " and two wide " lateral al?e."
The inner angles of the alse are rounded off; the median lobe pro-
jects beyond them and ends in a sharply defined, well-rounded, free
edge. The outer fourth of the transverse diameter of the median
lobe on each side is overlapped by the corresponding ala, a con-
siderable amount of matrix being occasionally interposed between
the two. The general plane of the median lobe, in fact, lies behind
that of the alse, whence it arises that impressions of the plate
present the aspect figured by M. Agassiz, and reproduced in
Plate III. fig. 2, and the median lobe, while covered by the alse,
appears spoon-shaped, whereas its end is in reality but little ex-
panded (fig. 7).

The alse present, very well developed, the peculiar sculpture so
characteristic of Pterygotus and its allies, multitudes of little semi-
lunar facets, with their convex edges raised and all turned towards
the convex margins of the plate, being thickly scattered over its
surface.

The facets of the sculpture on the middle of the median lobe are
greatly elongated, but have the same general direction. The rounded
end of the median lobe is marked by radiating strise, while its sides,
where overlapped by the alee, are smooth. From the thinness and
sharp definition of its edge, the median process would seem to
have been quite unconnected with the alse laterally ; and it appears
to have very readily yielded to force along the diverging grooves.
The impressions of median lobes detached, in consequence of
having broken away from the alse along these lines, are figured in
Plate III. figs. 3, 4.

No crustacean, living or extinct, is known to have a carapace
presenting the least approximation to the structure here described,
and the true carapace of Pterygotus has already been described. I
shall endeavour to prove by-and-bye that this singular plate is in
fact the homologue of the epistoma and labrum of other Crustacea.

3. The Body Segments. — Numerous oblong plates and impressions
of such, ornamented more or less extensively with the peculiar sculp-
ture, have been discovered (Plates IV. and V.). Of these, some are
much elongated transversely, and, if we may be guided by the
analogy of P. bilobus and perornatus, belonged to the anterior part
of the body. Others are longer than they are broad, and it may be
concluded, on similar grounds, that they represent posterior seg-
ments. In the specimen figured in Plate IV. fig. 6, two such seg-
ments remain in their natural relation to one another, but it is,
unfortunately, impossible to ascertain whether they simply over-
lapped one another and were merely connected by membrane, or

14 BRITISH FOSSILS.

whether their union was effected by a more definite articulation.
In Plate IV. fig. 1, a segment is seen to send a strong process for-
ward from its anterior and external angle, and a similar structure
appears to have obtained in the specimen figured by Professor
Agassiz, in the right-hand upper corner of his Plate A (loc. tit.}
This process may have served to articulate the segment with it&
predecessor, or it may have given attachment to muscles.

The specimen figured in Plate V. fig. 2, would at first appear to
indicate that the segment had a sub-circular or elliptical section,
but it is so much crushed and distorted, that I am not inclined to
lay any great stress upon the conclusions which may be drawn
from it, the more especially as all the other specimens which give
a view of the thickness of the body rather lead to the belief that
it was considerably depressed, at any rate, posteriorly. The seg-
ment, probably penultimate, figured in Plate V. fig. 3, for example,
exhibits no sign of having undergone any very considerable com-
pression, and yet its thickness does not equal more than one-fourth
of its breadth. It is quite possible, and indeed probable, however,
that the proportions of the antero-posterior and transverse diameters
may have been different in the anterior and posterior segments.

It is probable that the segments were sculptured on the ventral,
as well as on the dorsal surface, in all cases, as that last referred to
certainly is so. No segment has as yet exhibited any trace of an
appendage or of an articular surface for one.

A specimen in the possession of Mr. Lightbody exhibits at least
eight segments connected together, but there is no evidence as to
the total number composing the body of P. anglicus.

4 The Telson.— Reasoning from the analogy of P. acuminatus,
&c., the part figured in Plate V. fig. 6, must be the telson, or ter-
minal segment of the body, of P. anglicus. It is particularly
described in the systematic portion of this Monograph (p. 72). I will
merely remark, therefore, that it is oval, truncated anteriorly, mucro-
nate posteriorly, and serrated along the lateral edges. It presents
traces of a median ridge, and appears to have been very flat.

5. The paired Appendages. — The remains of three distinct kinds
of paired limbs, besides single appendages, have been discovered in
the same beds with the carapace and body segments of P. anglicus.
These are : —

(a.) The chelate organs figured in the most perfect state in which
they have yet been discovered in Plate VI. figs. 4, 5. Three
joints at least may be observed in this member. The first is an
elongated subcylindrical stem, flattened by pressure. The next,

BRITISH FOSSILS. 15

short, enlarged, and swollen, is produced into a long slender process,
pointed and incurved at its extremity, and beset with very strong
and numerous, unequal, striated teeth. The third joint is articulated
with the enlarged basal part of the second, so that its similarly
incurved extremity is opposable, like a thumb, to the latter. It
possesses teeth of a similar structure to those in the other ramus of
the chela, and opposed to them as the canine teeth in the upper jaw
of a mammal are opposed to those in the lower, passing, that is,
behind the others, or on their proximal side.

(6.) The second kind of appendage (Plate VII. figs. 4, 5, 6, 7,)
presents a large flattened basal joint, produced at one extremity,
and truncated obliquely to its long axis at the other. The
truncated margin is slightly curved, and is beset with long and
strong, curved and pointed teeth, which are longer at one end of
the series than at the other ; and are so constricted at their bases,
as to appear to be articulated with the basal joint.

Of the two longest margins of the latter, the one has a general
convexity, while the other is concave. The outer part of the former
exhibits a sort of notch or step, in which is lodged the basal joint
of a long palpiform appendage. This joint (c) is very short and
somewhat swollen.

The next articulation (&, longer and subcylindrical, is broader dis-
tally than proximally. The third e), twice as long as the last, has
a nearly equal breadth throughout. It is exhibited in situ, and in
its whole length, by only one specimen (Plate VII. fig. 4), and here
the distal extremity is rounded and slightly emarginate.

In the same specimen (and only in this) a fourth joint (/) may be
observed. It is as long as the third, but of a different form, the
distal end being much wider than the rod-like proximal extremity.
The internal edge of the distal extremity is rounded and slightly
serrated, and is apparently the natural edge of the part ; but there
are appearances which lead one to suspect that the continuation of
the outer angle has been broken away.

The characteristic sculpture is visible upon the surface of the
basal joint of this appendage, more particularly towards the anterior
edge of its inner region, and the convexities of the facets are here
directed towards the convex long margin. The outer wall of its
outer region in fig. 4 is broken away, and the matrix contained in
the interior has become detached, so as to show the inner surface of
the opposite wall, which is perfectly smooth.

In the recent state a considerable interval, doubtless filled by
muscular and tendinous soft parts, must have existed between the

16 BRITISH FOSSILS.

two walls, as, even in the compressed fossil, the thickness of the
matrix filling the cavity sometimes amounts to one-sixteenth of an
inch. The third and fourth joints also had a considerable thickness.

(c.) Of the third kind of paired appendages the most complete
specimens are those figured in Plate VI. fig. 1, and Plate VII.
figs. 1, 2. It consists of an exceedingly large and expanded, quadrate,
basal joint, produced at one angle into a broad curved process, which
is obliquely truncated at its extremity. The truncated edge is
nearly straight, and is serrated, broad notches separating a number
of strong flattened pointed denticles, which are continuous with
the substance of the joint, and not articulated with it.

The denticles or serrations form a single series, and diminish in
size from one end of the series to the other. The smallest is suc-
ceeded by the rounded corner in which the truncated edge and the
concave margin of the serrated process meet.

The surface of the joint, and of its process, is covered with the
squamiform ornamentation, and presents in the middle of the
margin', opposite to the serrated process, a deep notch, which receives
the first joint of the long palpiform remainder of the appendage.

The form of these joints is particularly described below (p. 75).
I will only remark here that there are six of them, and that the
penultimate, much larger than any of the others, is elongated, broad,
flattened, and widely emarginate at its distal extremity, where it
articulates with an oval palette-like plate, with serrated edges. A
brief comparison of the figures will satisfy the reader that this is the
part represented by Professor Agassiz in the lower right-hand corner
of Plate A (loc. cit.}

From the form of the articulating edges of the joints of the pal-
piform part of this appendage, I am inclined to think that, as in
the chela of the lobster, the plane of motion of each joint formed
a considerable angle with that of its predecessor and successor, the
result of which would be a sort of feathering, or screw-propeller
motion, of the ultimate and penultimate joints during flexion of the
limb.

The Metastoma.— The last kind of appendage (Plate VI. fig. 7) I
have to describe is perfectly symmetrical, and hence, even if there
were no other means of determining its real nature, its single or
azygos character might be divined.

It is an oval plate with margins much thinner than the centre,
and presenting a median notch at one extremity. It is richly
sculptured, the facets having their convexities turned towards the
rounded entire end ; and it is worthy of notice that the facets are

BRITISH FOSSILS. 17

singularly close set around the apex of the emargination. It is as
if the plate had been once completely oval and evenly ornamented,
and had then been folded in at the emargination.

The part represented in Plate VII. fig. 7, closely resembles the
basal joint of the appendage described under the head (6) in general
aspect, but differs from it in the excavation of the more convex
margin, in the length of the latter, and in the fact that the longest
tooth arises considerably behind the junction of the curved with
the truncated margin. If these appearances do not arise from
mutilation or other alteration, this part is probably a fourth paired
appendage.

The carapace of Pierygotus anglicus has not been found in con-
nexion with the body, nor the epistoma with the carapace, nor any
of the appendages with any other part of the body. A peculiar
value consequently attaches to those entire specimens of a crusta-
cean formerly denominated Himantopterus, but which the further
information yielded by the. extensive materials on which this
Monograph is based, shows to be of doubtful generic distinctness
from Pterygotus.

A well-preserved specimen of P. (Himantopterus) kilobits is
represented in Plate I. fig. 1. It presents an elongated body,
rounded anteriorly and posteriorly, and much narrower in its pos-
terior, than in its two anterior, thirds. Assuming that the dorsal
surface of the animal is exhibited, there lie, on its right side, the
remains of two appendages, the anterior disposed so that its long
axis crosses that of the body nearly at right angles, and passing by
its inner extremity into the middle of the anterior margin of the
head ; the posterior, lying more nearly parallel with the axis, and
traceable forwards, only so far as the posterior margin of the anterio
segment or carapace.

The latter has a nearly semicircular outline, but is more produced
than a true semicircle would be. On the right side the margin is
interrupted by a much elongated oval depression, having its long
axis directed forwards and inwards. This is the impression of the
eye, and in some specimens it shows a sculpture very similar to
that seen upon the eye of P. anglicus.

The carapace is succeeded by a number of segments, of which the
best preserved specimens exhibit twelve. The anterior ones are
transversly, the posterior longitudinally, elongated, and the hinder-
most, or telson, is oval and deeply emarginate posteriorly. In front
of the head, in the specimen figured in Plate I. fig. 1, and apparently
connected with its anterior boundary, lies a semicircular plate with

[1.] B

18 . BRITISH FOSSILS.

its convex edge turned forwards (a). The plate is as broad as the
head, but not quite half so long, and its longitudinal axis is oblique
to that of the body. In the middle line, it presents a flattened area,
bounded by a longitudinal ridge on each side, and rounded off in
front. Although the structure of this part is somewhat obscure,
I have little doubt that it corresponds with the epistoma of
P. anglicus, and that it has been thrust out of place and thrown
forward.

To the right-hand side of the carapace, opposite the anterior half
-of the eye, two curved, serrated, linear impressions, convex inwards,
.appear (fig. la). The anterior and inner of these is not more than
half the length of the posterior and outer, and cuts the latter about
its middle. I find no corresponding impressions upon the left side.
When the impressions are viewed very carefully with a magnifying
glass, in a good light, they present minute but important differences
The serrations of the short impression are concave and striated, and
constricted at their bases. Those of the long impression, on the
other hand, are flattened and not constricted, and their series is
terminated, posteriorly, by a rounded lobe which forms the posterior
angle of a broad process whose boundaries become lost externally.
Sufficient, however, remains to show the correspondence between this
part and the serrated process of the appendage (c) of P. anglicus,
while the teeth of the inner and shorter line are strikingly similar
to those which beset the edge of the basal joint of the appendage (&)
in that species.

That the impressions in question are in fact the remains of
appendages similar to (6) and (c) becomes a matter of certainty
when we examine such specimens as those figured on Plate I.
figs. 3, 4, 8, 9.

In fig. 8. is represented an organ, certainly belonging to P. bilobus,
whose basal articulation has as nearly as possible the same form as
that of the appendage (c), and presents, along its free edge, the same
continuous serration and posterior rounded lobe. The like resem-
blance is traceable in the joints of the palp -like appendage, except
that in this specimen a structure was observable, not visible in any
other, whether of the same or of different species. This is a long taper
filament, nearly as long as the ultimate and penultimate joints,
lying on their surface, and apparently attached by its thicker end to
the distal extremity of the antepenultimate articulation. There are
indications that this filament was itself jointed. In figs. 3, 4, 9,
the whole appendage, or at any rate its basal joint, is seen in situ,
and on comparing the serrated edge of any of these with the outer

BRITISH FOSSILS. 19

linear impression first described, the source of the latter will be
obvious.

The base of this great limb is attached to the hinder part of the
carapace ; it therefore, without doubt, lay behind the mouth, and
as it is the outermost pair of buccal appendages, it will be useful to
call it the " ectognath," a term more convenient than " maxilla,"
" maxillipede," or " swimming-foot/' as it involves neither a morpho-
logical nor a physiological hypothesis.

The organ which caused the shorter linear impression, lying-
internal to and in front of, that of the cutting edge of the ectognath
is, I doubt not, similar to that which lies detached in two speci-
mens, and is figured in the woodcut, p. 40. It is unfortunately
impossible in either of these examples to trace, as distinctly as might
be wished, the precise form of this appendage, but enough is visible
to satisfy me that this species was provided with one, if not two,
organs on each side similar in general structure to the appendage (6)
of P. anglicus, and quite competent to produce the impression in
question.

From its general character I entertain very little doubt that the
appendage (6) is the homologue of the mandible of other Crustacea,
but as there is some reason to suspect the existence of a third buccal
appendage, and as it is impossible as yet, supposing this third jaw
to exist, to say whether any given appendage similar to 6. was first
or second in order, it will be better to term an oral limb in front of
the ectognath, an "endognath." The specific name of" mandible"
must be assigned to whichever of these endognaths further research
proves to be anterior.

The position and general nature of two of the three pairs of
appendages of Pterygotus having thus been determined, the third
presents no difficulty. In the specimens of P. bilobus, represented
in Plate I. figs. 1, 3, indeed, the pair of long anterior appen-
dages are so much distorted and damaged that their structure
cannot be satisfactorily made out. There is abundant evidence,
however, to show that they were similar to the detached chelae
figured in Plate I. fig. 6, and these are obviously identical with
the pincer-like appendage (a) of P. anglicus.

The epistoma has already been recognized in the plate lying in
front of the head, in Plate I. fig. 1 ; it remains only to discover the
representative of the metastoma, and the position which it occupied
in the organism. The form and sculpture of the part represented
in Plate I. figs. 10, 10 a, testify that it answers to the organ sought,
and a careful examination of most well preserved carapaces of

B 2

20 BRITISH FOSSILS.

P. Ulobus, shows a corresponding plate, or its impression, in situ.
When undisturbed, in fact, the metastoma occupies the middle of
the under surface of the carapace, the cutting edges of the basal
joints of the gnathites overlapping, or being overlapped by, its lateral
margins, and its emarginated extremity being turned towards the
anterior end of the head, which it nearly reaches. The posterior
rounded margin is in contact with the posterior boundary of the
carapace.

A part, having this form and occupying this position, might be
regarded as a labrum or as a metastoma. My reasons for giving it
the latter appellation are the following : — It may be regarded as
pretty certain that in Pterygotus, as in other Crustacea, a sculptured
surface was free and uncovered by other parts, in which case the plate
could not have been attached to the inner surface of the epistoma
by its sculptured anterior and outer surface ; nor, for the same
reason, could it have been attached by its inner surface to the
sculptured outer surface of the epistoma. The anterior margin of
the plate reaches so far forwards that it could not have been
attached by that margin to the posterior margin of the epistoma ;
and. furthermore, when the latter is detached or thrown out of
place the metastoma is never found connected with it, but, as in
fig. 1 , Plate I., remains in its own proper position.

I have little doubt, therefore, that this plate was attached by its
posterior extremity to the under surface of the hinder half of the
carapace ; that it lay behind the mouth, and had all the relations of
a metastoma, and it will be seen by-and-bye that certain existing
Copepoda possess a metastoma very like it, except in its very great
proportional size.

Putting together the different facts furnished by the remains of
the two species of Pterygotus, which have been described, it
results, —

1. That the body in this genus was composed of a number 01
segments, which might be thirteen in number.

2. That these segments exhibit a peculiar ornamentation.

3. That the terminal segment, or telson, is liable to considerable
specific variation.

4. That the anterior segment is larger than the rest, and forms a
carapace, on whose antero-lateral margin two large oval convex
eyes are seated.*

* Notwithstanding the peculiar character of the markings upon the corneal surfaces of
these eyes, 1 wait for better evidence than I have hitherto met with, before deciding that
they were really compound, and that these markings indicate corneal facets.

BRITISH FOSSILS. 21

5. That, attached to the under surface of the carapace, there are
eight (or ten) distinct organs, two single and .median, and three or
four pairs.

6. The former are, in front, the great emstoma ; behind, the
metastoma ; between these lay the oral aperture.

7. The latter are, anteriorly, the ch elate organs (antennae) ;
posteriorly, the ectognaths, immediately in front of which lay one
or two pairs of endognaths.

8. That there is no good evidence of the existence of any other
appendages.

Almost all the remains certainly assignable to Pterygotus, which
have passed through my hands, are easily referable to one or other
of the classes of organs mentioned above, and exhibit no anatomical
peculiarities worthy of comment, but a few specimens present diffi-
culties to whose discussion I will now proceed.

1. Pterygotus punctatus. — The only representative of the
endognaths of this species which I have examined (Plate XI. fig. 5)
exhibits a structure somewhat different from that of the perfect
endognath of P. bilobus and anglicus. The anterior and internal
angle is rounded off ; the series of teeth commencing behind, and
not at the anterior extremity of, the inner edge. The straight
inner portion of the anterior margin is spinose, and forms a con-
siderable angle with the outer portion, which bears the palp.
The latter is four-jointed, the proximal articulation being large,
quadrate and setose along its anterior margin, and provided with
a large and strong curved spine towards the outer extremity of that
margin. The next joint is elongated and curved, its posterior
margin being slightly convex, the anterior similarly concave, and
towards the distal extremity bearing a curved spine, like that in
the preceding joint.

The third joint and the fourth are much shorter. The former
carries a spine on its anterior edge. The latter has two spines,
one anterior and one terminal. Is this the homologue of that
endognath of Pterygotus anglicus represented in Plate VII. fig. 4,
or does it, as the structure of its basal joint would seem to indicate
correspond with the apparently different part shown in fig. 7 ?

2. Pterygotus acuminatus. — On the same slab with a large por-
tion of the body and one of the ectognaths of this species, is seen the
remains of an appendage whose basal joint clearly resembles the
corresponding part in P. anglicus (Plate XIII. figs. 2, 3.) It con-
sists of a broad, flattened, quadrate plate, having a series of curved
and striated teeth articulated with its well-defined, nearly straight,

22 BRITISH FOSSILS.

edge. These teeth, however, do not form one even series, either
as 'regards their size or their position. They commence large, near
to what I will term the anterior margin of the plate, but not
close to it, the antero-lateral angle being rounded off and
oiving rise to no tooth. In this respect it represents the corre-
spondincr part of the endognath of P. punctatus just described.
After four or five large ones, the teeth rapidly diminish in size and
become indistinguishable. The free edge of the plate then makes a
slight curve, so that it projects beyond its former line and then gives
rise to two teeth of the same size as the most anterior ones, after
which it becomes lost beneath the matrix. A depression runs from
the commencement of this projecting edge into the crushed and
transversely folded, middle part of the plate. In front of this
crushed portion, the anterior region of the plate is, in its outer half,
richly sculptured ; behind and internally, the substance of the organ
is for the most part broken away, but shows the remains of a
similar sculpture outside the broken edge. The opposite half of
the specimen exhibits the impression of the sculpture over this
broken part, but in neither half can the ornamentation be satisfac-
torily traced continuously over the middle crushed region.

The outer part of the joint, just described, is continued into a broad
mass, so divided into two portions externally, as to appear like two
palps. Each palp-like division appears to possess at least three
joints, and the distal margins of the outer of these joints in the
anterior " palp " are produced into strong curved processes or seta3.
. The part represented in Plate XIII. fig. 4, apparently consists of
these palpiform appendages detached from their basal joint. Four
or five gradually tapering joints are here distinguishable, and each
is produced into setaB along it distal edges, while the terminal
articulation resembles a curved claw.

The same kind of basal plate, apparently provided with similar
appendages, is shown in another specimen (Plate XIII. fig. 3), but
the parts are here overlapped by the broken ectognath, and are so
crushed and confused that I can arrive at no satisfactory conclusion
regarding them.

A valuable example of P. acuminatus from Lesmahago
(Plate XV. fig. 1), although greatly crushed, and at first sight very
unpromising, yields a great deal of valuable information on patient
investigation, and shows, among other things, that the organs under
discussion belong to the mouth and to the endognathary series. In
fact, in both halves of this specimen, the ectognath and the meta-
stoma are very clearly traceable, and are evidently almost undis-

BRITISH FOSSILS. 23

turbecl. The palps of the ectognaths are displayed in situ on each
side ; the cutting edges of these appendages are seen on each side of
the middle line and are turned towards one another, while the large
metastoma lies between them, overlapping their respective inner
margins. Internally to their serrated edges, a series of articulated
teeth (c'), like those connected with the free edge of the basal joint
of the organ described above, can be seen upon each side, but the
rest of the basal joint cannot be made out.

On the left-hand side of the head, however, the remains of two
palpiform bodies (c), evidently of the same nature as those described-
above, and provided with similar strong curved setae, are visible.
On the right side is an impression of a similar character, but its
minutiae cannot be satisfactorily deciphered.

The facts I have detailed may be variously interpreted. Either
the two palps belong to one basal joint, or there are two basal
joints, each with a palp. In the former case there would be one
endognath on each side, with a double palp ; in the latter, two
endognaths, each with a single palp. As the evidence stands at
present, I see no means of arriving at a well-grounded opinion on
this subject, and I prefer to abstain from conjecture.

3. Pterygotus peromatus. — The opposite impressions of part of
an example of this species are exhibited by two slabs, each of
which shows more or less distinctly the carapace and one of the
body segments.

On the larger slab (Plate XV. fig. 2), the impression of the
metastoma is distinguishable within the outline of the carapace,
but it is thrown out of place, so that its long axis is directed
obliquely forwards and to the right side, at an angle of forty-five
degrees to that of the body. Close to the anterior extremity of
the metastoma, but projecting beyond the boundary of the carapace,
lies the basal joint (c) of an appendage with articulated, curved,
pointed and striated, teeth, like those of the endognaths of the
preceding species.

The dentated edge of this organ lies almost parallel with the long
axis of the metastoma; but beyond it, and more towards the middle
line of the body, there is another curved edge (c'), similarly provided
with striated and articulated teeth, but cutting the first at a large
angle. Is this part of a second endognath of the same side, or is it
that of the other side turned round ? In any case the parts are
thrown far out of their natural position.

On the left-hand side, between the base of the metastoma and the
middle of the lateral margin of the carapace, the imperfect impression

24 BRITISH FOSSILS.

of part of the toothed edge of another appendage (c") is discerni-
ble. It is turned backwards (so that it is certainly displaced), and the
teeth are somewhat curved and striated. If there are two endo-
gnaths on each side, this might well be one of the left pair turned
round.

On the left-hand side, the palp (e] of the ectognath is in position,
but nothing is to be seen of its basal joint. On the right-hand side,
the large basal joint of an ectognath lies detached and turned round,
so as to have its cutting edge directed backwards. A confused mass
occupies the place of its palp.

Where the antennse should be there is, on the left side, a long and
broad dark impression (6) fading away externally. On the right side
there is a somewhat similar marking which continues the line of
that on the left hand, but is very broken and irregular. However,
it divides distally into two branches, on the opposed edges of which
the remains of the characteristic antennary teeth can readily be
discovered (6').

Whether these impressions represent one antenna, or portions of
both, I cannot say, but between them, and in front of them, a dark
sculptured area (/) presents itself, which is cut off anteriorly by the
fractured edge of the stone. On the right side, this area is bounded
by a well-defined margin, which runs between the posterior boun-
dary of the antenna, and the inner of the two endognaths. On
the left side, its well-marked curved boundary is distinguishable
between the antenna and the broken edge of the stone.

Towards the junction of the middle and anterior thirds of the left
lateral edge, a long, flattened, filiform appendage (c) comes off from
the carapace. On the right side, the remains of two such appen-
dages, with, perhaps, traces of a third, are visible (x). They come
off close to the two endognaths, and one might be inclined to
suppose them all organically connected with the latter, were it not
for the independent appendage on the opposite side.

In the other, smaller, half of the specimen the only points to be
noted are, the greater distinctness of the right boundary of the
"sculptured area" in front of the carapace, and of the right (here left)
filiform appendages. I am strongly inclined to think that the
" sculptured area " in this fossil is the epistoma. The interpretation
of the filiform impressions is more difficult. That on the left side
seems to be attached directly to the carapace, and in that case might
be a second antenna. If this be its nature, the impressions on the
other side may be the corresponding appendage and the palps of the
endognaths. On the other hand, it must be remembered that there

BRITISH FOSSILS. 25

is no independent evidence of the existence of a second antenna in
the genus, and that the position of the filiform appendage on the
left side may be purely accidental.

4. The two singular fossils figured in Plates XII. fig. 16, and
Plate XIII. fig. 16, are the only remains, which, from their sculpture,
may be, with every probability, referred to Pterygotus, but which
are not as yet referable to their proper place in the organization.

These parts present, at first sight, a striking resemblance to the
terminal palette of an ectognath, with a portion of the penultimate
articulation. They are described at length in the systematic por-
tion of this Monograph (p. 97) ; and I will, therefore, only remark
in this place that, as the ectognaths of P. problematicus and
arcuatus (the species to which these remains probably belong) have
not yet been observed, it is possible that they may be their distal
joints. Pending sufficient proof that such is the case, however, it
must be borne in mind that they differ in several important respects
from any ultimate and penultimate joints of an ectognath at present
known. The only alternative which suggests itself is that these
parts may have been thoracic or abdominal appendages.

5. The fossil figured in Plate XIII. fig. 17, is evidently crustacean,
but it exhibits no character by which it can be identified as a part
of a Pterygotus. It is a broad quadrate plate, abruptly truncated
on two of its opposite sides, one of which is much longer than the
other, and having the other two margins equal and rounded. Two
folds or ridges run from one truncated edge to the other, and divide
the plate into three lobes, a median and two lateral. The median
lobe presents a series of curved lines or ridges disposed symmetrically
on either side of the median line. Similar folds in the one lateral
lobe are more or less symmetrically arranged with regard to those
on the other lobe.

The shorter truncated margin of the plate presents two
impressions, like the remains of articular surfaces, and there are
similar impressions at the outer extremities of this margin. Of
these, that 011 one side gives attachment to a long jointed appen-
dage presenting six distinct articulations. The basal joint is short
and much wider than the others. The distal edge of the fourth
presents a series of strong spines, the sixth has the form of a curved
claw.

I know of only two crustacean structures with which this body
can be compared, the one is a carapace, the other the swimming
limb of a copepod with its coalesced, lamellar, basal joints greatly
developed (compare, Plate XVI. fig. 7).

26 BRITISH FOSSILS.

Systematic Position of Pterygotus.— In comparing Pterygotus
with other crustaceans, for the purpose of determining its systematic
position and relations, several of the largest and best denned orders
of the Crustacea may at once be left out of consideration. Ptery-
gotus is clearly not one of the Trilobita, Cirripedia, Ostracoda,
Edriophthalmia, or Stomapoda (if we restrict this order to these
Crustacea which have pedunculate eyes, and distinct and moveable
ophthalmic and antennulary somites). Nor are there any known
Branchiopoda to which these great extinct crustaceans have relations
of affinity, so that if they are to be referred to any existing order, it
must be either that of the Podophthalmia, that of the Copepoda, or
that of the Pcecilopoda.

The first step towards determining the systematic place of
Pterygotus, therefore, is to consider the reasons for and against the
assignment of a position in either of these orders to them.

To those who are acquainted only with the ordinary Podoph-
thalmia, the discussion of the affinities of Pterygotus, with forms in
every way so distinct, may seem superfluous ; and there is assuredly
little enough in common between a crab or a shrimp and their palaeo-
zoic congeners ; but there are one or two sections of the Podophthal-
mia which, while they still hold fast by the typical characteristics of
their order, become so modified in many important particulars, as to
require careful consideration in relation to the forms at present under
consideration. These are the Diastylidce or cumoid Crustacea.

The typical genera of this group were first described by Mr. H.
Goodsir, and they have since been the subjects of excellent essays
by Kroyer and Spence Bate.

Cuma Rathkii (Plate XVI. figs. 17, 18) may be selected for
description as a good representative of the family. The animal
presents anteriorly a short and broad carapace, having its outer and
lateral edges rounded and sloping into a bifid, median, anterior,
rostrum-like prolongation. The longitudinal fissure of this process
divides posteriorly on the carapace, so as to embrace the anterior
part of a more convex median lobe, which represents the tergal
region of the head. The bifid median prolongation is not, as it-
appears to be, a frontal rostrum, but it is formed by two lateral
processes of the carapace, which come forward and are applied to
one another in front of the head.

The carapace is succeeded by five broad thoracic somites, and
these by six, narrower and longer, abdominal somites and a telson.
The sixth abdominal somite has styliform appendages, but in the

BRITISH FOSSILS. 27

female there are no other abdominal limbs, and in the male such
as exist are few and rudimentary.

Of the appendages, the eye is median, sessile, and not easily made
out in spirit specimens ; there are a pair of antennules, a pair of
antennae and of mandibles, two pairs of maxillae, and eight pairs
of thoracic appendages ; there is a a small labrum and a bifid metas-
toma ; but these parts have too little resemblance to any of the
organs of Pterygotus to need description in this place.

The most interesting feature about this crustacean in reference to
the present inquiry, however, is the ornamentation with which the
body and many of the appendages are covered. The surface of the
integument appears in many parts irregularly reticulated, but
elsewhere the reticulations assumes the form of a regular squamous
sculpture, singularly like that upon Pterygotus, but on a very much
smaller scale.

The general form of the body and the paucity of abdominal
members, combined with the peculiar sculpture exhibited by the
Diastylidce, attracted my attention strongly when, on a former
occasion,* I endeavoured to trace the affinities of Pterygotus.
Following the line of inquiry thus suggested, I pointed out that in
many Schizopoda and Stomapoda, such as Mysis, Phyllosoma, and
Erichthys, either the abdominal or some of the posterior thoracic
members, or both, became abortive, and that in the larval con-
dition of some Podophthalmia, even the sixth pair of abdominal
appendages remains undeveloped, and the abdomen is wholly devoid
of limbs. In the larval Brachyura or Zoece all the appendages but
the gnathites and antennae are rudimentary, and the long palpiform
maxillipedes are (in addition to the abdomen) the only organs of pro-
pulsion. The larval lobster (before hatching) is similarly deprived
of abdominal appendages, it possesses a disproportionately large
labrum, and a metastoma, which is only slightly emarginate an-
teriorly, and very large in proportion to the other buccal organs, as
compared with its adult state.

In the paper referred to, I laid considerable stress upon the
analogies, w^hich, from what has been said, may be readily enough
apprehended, between Pterygotus and the Diastylidce and larval
Podophthalmia. Renewed examination of the specimens and of
the far more extensive materials which have since presented them-
selves, aided by a careful investigation of the characters of the
recent Copepoda has shown me, however, that at least as strong a
* Quarterly Journal of Geological Science, vol. xii. 1855.

28 B1UTISH FOSSILS.

case might be made out for the relegation of the Pterygoti to the
latter order. (See p. 36, note.)

The evidence which has led me to this conclusion can only be
appreciated when the structure of the Copepoda is fully understood.
I will, therefore, proceed to give a- brief account of that structure,
and I am the more willingly led to do this as I have found it
difficult, notwithstanding the valuable labours of Milne Edwards,
Baird, Dana, and others, to arrive at a clear and connected view of
the anatomical characters of this difficult group.

The genus Calanus, containing a large number of marine species,
is perhaps best fitted to furnish a typical illustration of copepod
anatomy. The species represented in Plate XVI. fig. 1 , was taken in
the North Atlantic. It is about one-eighth of an inch long, and (after
preservation in spirit) has a lightish brown colour. The body pre-
sents a large carapace anteriorly, succeeded by a number of thoracic
and abdominal segments. The cephalo-thorax has the form of a
long oval, truncated and slightly excavated behind, the postero-
lateral angles of its last segment being but very slightly produced.
The abdomen has not a third the length of the head and thorax,
and is terminated by two elongated lobes provided at their extre-
mities with long setse. The antennules are as long as the body.
The cephalo-thorax consists of six segments, the anterior of which is
about equal to the three following ones in length, and forms a cara-
pace. The abdomen presents four obvious segments, but the first
appears to consist of two somites united together, and it is probable
that the two terminal styliform lobes may represent a somite, in
which case there would be six somites in the abdomen. The anus
opens between the bases of the terminal processes.

The carapace is not prolonged, either along its posterior margin or
laterally, but merely overlaps the tergum of the succeeding somite
in the ordinary manner. Anteriorly, it extends beyond the bases
of the antennules, and is produced forwards and downwards, be-
tween them, into two delicate pointed processes, slightly constricted
at their bases, which are about equal in length to the two basal
joints of the antennules. The latter are slender, of even thickness,
and divided into twenty-four setose joints.

An endophragm, or inflexion of the chitinous integument, dis-
tinctly separates the sternum of the antennulary, from that of the
antennary, somite. Viewed laterally, the former appears concave, its
posterior portion sloping backwards and downwards at an angle
with the anterior. The anterior half of the antennary sternum, on

BRITISH FOSSILS. 29

the other hand, is very convex, while its posterior half is produced
into an abrupt conical protuberance, behind which it passes into a
broad plate, with a free, convex, posterior edge. This projecting
mass developed from the antennary sternum appears to me to repre-
sent both the epistoma and the labrum of decapod Crustacea.

Viewed from below (Plate XVI. fig. 2) the part described has the
aspect of a very broad, almost triangular plate, occupying nearly the
whole width of the antennary sternum, and presenting a prominent
median portion and two lateral ate, which slope away backwards
and upwards. The posterior portion of the median lobe is rounded
and somewhat expanded at its extremity, and the lateral edges of
the expanded end are provided with fine seta3, which extend over
its superior face for a short distance. This conjoined epistoma and
labrum forms the anterior boundary of the oral vestibule; its inner
face is beset with short setse, and a short median tooth, rounded at
its extremity, projects backwards in the middle line.

Posteriorly, the oral vestibule is bounded by a quadrate plate, the
nietastoma, directed forwards and downwards, and having about
two-thirds of the width of the labrum. As the sterna of the two
somites which immediately succeed the mouth, viz., the inandibular
and the first maxillary, are not distinctly separated from one another;
it is difficult to say from which thin plate arises. I am inclined to
think, however, that it is really a production of the maxillary
sternum, as its posterior boundary lies behind the level of the
anterior margin of the base of the maxillse. The free anterior extre-
mity of the plate is deeply divided, by a wide median excavation,
into two lobes, which are provided with many short and fine setae.
A little, accessory, setose, lobule is also developed from the inner
surface of the plate on each side.

A well-developed endophragm separates the sternum of the first
maxillary, or second post-oral, somite from that of the rest. From
the mouth to the posterior edge of this, the third post-oral somite,
the sternal surface slopes gradually downwards ; but beyond this
point, or in the fourth post-oral somite, the sternum makes an abrupt
projection downwards and then passes backwards, with a general
parallelism to the axis of the body, for the rest of the extent of the
cephalo-thorax.

The antennse are about as long as the proximal nine or ten joints
of the antennules. They consist of a short basal portion supporting
two branches of about the same length. The basal portion is three-
jointed, the inner branch two -jointed, the outer multiarticulate.

30 BRITISH FOSSILS.

Neither antennules nor antennae are chelate or sub-chelate in
either sex.

The mandible (fig. 3") consists of a basal joint and a palpiform
appendage. The outer half of the former is quadrate, convex
inferiorly, and presents, posteriorly and externally, a curved
articular process ; the middle of the basal joint is a little con-
stricted and flattened, while its internal portion widens again, and
ends in a truncated, toothed edge. The teeth are continuous with
the blade of the mandible, not articulated with it. The palp
springs from an excavated surface on the anterior and superior
face of the quadrate outer division. Its proximal joint is short
and rounded. The next is the longest, and as broad as or broader
than the basal joint, and wider distally than proximally. At the
distal end it supports two branches, the outer of which is
obscurely five-jointed ; the inner two-jointed. The toothed and
cutting extremities of the basal joints of the mandibles pass
between the labrum and the metastoma, and bite against one
another in the middle line. Those of the maxillae lie behind the
metastoma. The first maxilla (fig. 4) is nearly of the same size as the
mandible. Its basal joint is produced internally into a large curved
process, whose inner edge is beset with strong articulated setae,
which might almost be called elongated teeth, were they not setose
along their edges. Succeeding this articulation is a broad joint
produced internally into a narrow, transversely elongated, flattened
process, terminated by elongated setigerous setae externally, into a
broad flat plate bearing eight or ten extremely long and strong seti-
gerous setae ; five other obscurely marked joints follow these two.

The next appendage (fig. 5) is not quite so long as that just
described; it is obscurely divided into seven joints and tapers
to its extremity, which, like its inner edge, is provided with very
long and strong setae. The inner setae are by far the stronger,
and are directed forwards so as nearly to reach the mouth.

The fourth post-oral appendage (fig. 6) is more than twice as
long as the third. It consists of a short and strong, subcylindrical,
basal joint, beset along its inner margin with a row of very long
setigerous setse, and having a rounded projecting inner distal
angle. One long and five short gradually diminishing articulations
follow this.

To this appendage succeed the five pairs of swimming feet (fig. 7),
of which the first and the last are smaller than the intermediate
ones. Each natatory limb consists of a stem (protopodite) and two

BRITISH FOSSILS. 31

branches (endopodite and exopodite). In the former a long-
proximal and a short distal joint are distinguishable. The
proximal joint is united, for a considerable part of its length, to its
fellow on the opposite side by a flattened plate, continuous above with
the sternum, and thickened by a spatulate ridge in the middle line.

The distal joint has the inner half of its terminal margin more
produced than the outer. The former bears a shorter (endopodite),
and the latter a longer, three-jointed branch (exopodite). The
terminal articulation is the largest, and is provided with long and
strong setse.

The inner edges of the basal joint of the protopodite of the
fifth pairs of these feet are beset from their distal extremities to the
uniting plate with a series of short, but strong and pointed teeth.

On considering the structure of Calanus with reference to the
general plan of the Crustacea, I may observe, in the first place,
that of the twenty typical somites, only eighteen, at most, appear
to be represented. We may reckon one, for the eyes ; two, for the
antennules and antennae ; four, for the four pairs of post-oral
appendages ; and five, for the swimming feet, making, in all, eleven,
provided with moveable appendages. Then, if the first segment
of the abdomen be really formed, as there is much reason to believe
it is, by the coalescence of two somites, and if the two caudal
styles really represent another, we shall have six somites in the
abdomen, making up the sum total to eighteen.

This number cannot by any means be made out in all Copepoda,
but I know of no members of the order which exceed it.
Different opinions have been entertained with respect to the
grouping of these somites into cephalic, thoracic, and abdominal.
The eyes, antennulse, antennae, and the two anterior pairs of post-
oral limbs, and with them their somites, are indeed universally
admitted to belong to the head ; but the two following appen-
dages are considered by some to be maxilla3, by others to be
maxillse and maxillipedes ; by yet others to be maxillipedes and
anterior thoracic limbs.

The simplest and most natural view appears to me to be, to
regard the third pair of post-oral appendages as the homologues of
the second maxillse or last cephalic appendages, while the fourth
post-oral appendages are thoracic members. In this case there will
be six pairs of thoracic appendages, as in the Cirripedia. If we
inquire what has become of the two thoracic somits which are unre-
presented by appendages, three probabilities present themselves : —
1. They have remained undeveloped at the anterior end of the

32 BRITISH FOSSILS.

thorax ; or, 2, they have remained undeveloped at the posterior
end of the thorax ; or, 3, the two somites which are so closely
united together as to appear as one segment, commonly regarded as
the first of the abdomen, belong in reality to the thorax. This
view might be supported by the position of the reproductive
apertures which open behind the second of these somites, that is,
on this hypothesis, in that position immediately behind or at the
posterior part of the thorax, which is so common to them in
Edriophtlialmia, Pcecilopoda, and male Podophthalmia. If this
view be correct, (but I would expressly state that it is put forth
only tentatively,) it is the abdomen alone, which is shorn of its due
proportions in Copepoda.

Such is the structure of a typical copepod. The modifications
observable in the order, of importance for my present purpose,
affect, — Istly, the form of the body ; 2ndly, the character of the eyes ;
3rdly, the form of the antennules and antennae ; 4thly, that of the
lab rum and metastoma ; 5thly. the number of the thoracic
appendages.

1. The body usually has a general resemblance in outline to
that of Calanus, the abdominal somites commonly presenting a
marked and immediate diminution in transverse diameter when
compared with those of the cephalo-thorax. In the beautiful
Sapphirince. (Plate XVI. fig. 19), however, the passage from the
cephalothoracic to the abdominal somites is quite slow and gradual.

2. In most Copepoda the eyes are so closely united as to
appear single, and the region of the carapace which overlies them
is not so modified as to deserve the name of a distinct cornea. But
in the genus Sapphirina (Plate XVI. fig. 19), there are two small
single eornese approximated together in the middle of the dorsal
surface of the carapace ; and a still more interesting modification of
the visual organs is presented by Corycceus (Plate XVI. figs. 8, 9).
Here two great, oval, spectacle-like, corneas are situated, one on each
half of the anterior rounded margin of the carapace.

3. The antennules and antennas vary very much in form. In
many Copepoda they are so constructed as to subserve prehension,
either for sexual or other objects. The antennules are thus
specially modified in the males of Pontella and Cyclops, while in
CoryccBUS these organs remain simple ; but the antennae (III/) are, in
both sexes, converted into formidable weapons. It will be observed,
however, that prehension is effected by the folding of the ultimate
upon the penultimate joint, not by the biting of the apex of the
ultimate joint against the prolonged distal angle of the penul-

BRITISH FOSSILS. 33

timate. It is a subchela such as is found in Amphipoda and
Stomapoda, not a chela like that of Podoptithalmia and
PcecilopodcL

4. The plate, which corresponds with the conjoined epistoma
and labrum of decapod Crustacea, is very large in all the Cope-
poda I have examined. Its form and proportions in Calanus,
Corycceus, and Pontella are shown in (Plate XVI. figs. 2, 9, 11). In
the last-named genus it exhibits, as Milne Edwards has pointed out
in his great work on the Crustacea, the remarkable peculiarity of
being divided into three lobes, of which the middle is the smallest,
and constitutes a kind of tongue-like projection (fig. 11).

5. The metastoma of Calanus, as has been stated above, is
excavated anteriorly by so deep and wide an emargination, that it
almost appears to consist of distinct lobes. In Pontella, on the
other hand, the metastoma is a large flattened plate, whose ter-
minal emargination, though wide, is not deep (fig. ] 1).

6. In Calanus, nine pairs of post-oral appendages have been
found, the greatest number possessed by any masticating copepod.
In Corycceus and Cyclops this number is reduced to eight, and of
these the last is occasionally so much atrophied as to be hardly
distinguishable. We have thus evidence of a certain tendency
towards a diminution of the number of thoracic appendages in this
order.

The study of the development of the Copepoda shows that this
is no more than might be expected, when we take into consideration
how common a thing it is, for some form of a group to retain more
or fewer of the characters usually found only in the young of that
group ; and perhaps the only subject for astonishment is that adult
Copepoda, with still fewer limbs, have not yet been discovered. A
Copepod just hatched is, in fact, a very different creature from the
adult, as has been known since the observations of Jurine upon
Cyclops.

Rathke, who has devoted particular attention to the development
of the embryo in this genus, maintains that of the three pairs of
locomotive appendages, with which alone, the young is endowed
when it leaves the egg, the two anterior eventually become the
antennules and antennae, while the posterior are neither the man-
dibles nor the first pair of maxillae, but the rudiment of the " mains"
of Jurine. The young Cyclops is in addition provided with a large
epistomo-labral plate. Its further changes consist chiefly in the
elongation of the body, and the gradual and successive acquisition,
of the thoracic members.

[1.] c

34) .BRITISH FOSSILS.

The resemblances of Pterygotus to the Diastylidce do not extend
to the most important and characteristic features of its organization,
and even were we to combine together into one form, all the
analogous peculiarities which have been noted in these, in Stoma-
poda, in Schizopoda, and in larval Podophthalmia, we should not
get a sufficiently near approximation to Pterygotus to justify
the arrangement of the extinct genus in either of the orders of
the higher Crustacea. As I hinted above, however, a stronger
case might be made out for the Copepoda. Combine the body
of Sapphirina with the eyes and antennse of Corycceus, the man-
dibles and maxillae of Calanus, the epistoma and metastoma of
Pontella, and the total number of appendages of a copepod larva,
and something marvellously like a Pterygotus would be produced.
But such an animal would not be a Pterygotus, and even if it
were, it would differ so widely from any of the known Copepoda,
that its association with the members of that order would be a step
of very questionable propriety. Confining the argument to known
and existing Copepoda, the differences between them and Ptery-
gotus are sufficiently striking.

No Copepod has truly chelate antennse or antennules, and none
present any approximation to the remarkable teeth with which the
chelse of Pterygotus are beset. All known Copepods have large
thoracic appendages ; no trace of such organs has yet been discovered
in Pterygotus.

No Copepod, so far as I know, presents so great a number as
twelve free segments behind the carapace.

No Copepod has its appendages reduced to so few as three or four
pairs, nor, in any, is one pair of the post-oral cephalic appendages
converted into the chief organ of locomotion.

The Pcecilopoda (Plate XVI. fig. 13) are I believe the only Crus-
tacea which possess antennary organs like those of Pterygotus, and like
them, have the gnathites converted into locomotive organs, want the
appendages to the sixth abdominal somite, and present on some parts
of the body a remotely similar sculpture. In this order, however,
we find but a small labrum, — a rudimentary metastoma, — a very
differently constructed body, and a large number of appendages, both
thoracic and abdominal, characters which effectually preclude the
association of the extinct Crustacea under discussion with this
type.*

* If the abdominal somites of the Carboniferous Bellinurus, &c. were really free, they
•would present a certain approximation to the Pteryyoti. Indeed, the evidence that these
Carboniferous Crustacea were true Pacilopoda is, to my mind, anything but conclusive.

. BRITISH FOSSILS. ' 35

The palp of the mandible of Nebalia (Plate XVI. fig. 10) is, in its
: proportional size and form, not unlike that of Pterygotus anglicus,
but this is the sole resemblance of importance which I can detect
between the Branchiopoda and the Pterygoti.

While the relations of the Pterygoti with the great majority of
other Crustacea, are such as, in my mind, fully to justify their ordinal
separation, there is one small and extinct group, having a similar
geological range, with which they are undoubtedly closely connected.
This is the genus Eurypterus of Harlan, of which many species have
now been brought to light. Putting together the descriptions of
Harlan, Eichwald, Roemer,* and others, with the results of a personal
inspection of some species recently described by Mr. Salter, I can
only arrive at the conclusion that, in its general form and structure,,
Eurypterus very closely resembled Pterygotus, differing from it
however as Sapphirina differs from Corycceus, viz., in having the eyes
submedian instead of marginal. The ectognaths of Eurypterus
appear to have been constructed upon precisely the same plan as those
of Pterygotus, and its thoracic and abdominal members would seem to
have been equally undeveloped.! Eichwald describes twelve segments
behind the carapace (though only eleven are represented in his figure).
Two pairs of slender jointed appendages are figured both by him|
and by Harlan in front of the ectognaths ; but no chelate antennae
are represented, and the connexions of the jointed appendages are
not made out. The characteristic sculpture is well exhibited by
Eurypterus. Even if the chelate antennae are really absent in
Eurypterus, it must be remembered that these are organs particu-
larly liable to variation among even closely allied genera of
Copepoda,

Leaving the determination of the precise differences between the
Pterygotus and Eurypterua to future investigators, their resem-
blances to one another, and their common differences from all other

* Ferd. Roemer. Ueber ein bisher nicht beschriebenes Exemplar von Eurypterus aus
Devonischen schichten des Staates New York in Nord-Amerika. — Dunker und Von Meyer's
Paleontographica, b. 1, 1851, p. 190.

f Eichwald's representation of the under surface of the head is terribly diagrammatic.
If it be a correct representation of an actual object, it affords evidence of only three pairs of
appendages. His " two large, almost semilunar, lateral parts " appear to me to be the
basal joints of the ectognaths, while the middle ovate "under lip" has just the position
and general form of the metastoma. Add to these the triangular " upper lip," and the
resemblance to Pterygotus becomes not a little striking.

J Roemer states that his Eurypterus also had twelve free segments behind the carapace.
The eyes borne by the latter were uniform and not facetted ; only two appendages, both
on the left side, remained. The posterior had the general structure of the ectognathary
limb of Pterygotus. The anterior is slender, four-jointed, and perhaps terminated in a
chela.

c 2

36 BRITISH FOSSILS.

Crustacea, are sufficiently important to justify their association into
a distinct order — the " Eurypterida" which may be thus denned :
Crustacea with numerous free thoracico-abdominal segments, the
penultimate, and probably all the rest of which, are devoid of appen-
dages ; with the anterior somites united into a carapace, bearing a
pair of large marginal or subcentral eyes ; with a very large epistoma
and metastoma ; with three, or four pair of moveable cephalic ap-
pendages, the posterior of which form great swimming feet, and
with the integument characteristically sculptured.

Of the mode of life of these extinct Crustacea we know nothing,
but we may conjecture that it was their habit sometimes to creep
along the bottom of the waters which they inhabited, like theLimulus
of the present day, sometimes to propel themselves by the rapid
flexion of their great swimming feet, aided perhaps by the sudden
extension of their free segments.

No existing or extinct crustacean has so massive a body as
Pterygotus, some species of which there is every reason to believe
attained a length of at least five feet ; but mass, in an active animal,
involves large muscles, and these require solid points d'appui.
Hence we may conclude that the integument of the Pterygotus, thin
and fragile as are its remains, possessed a great amount of firmness
in the recent state.

That the singular thinness of the fossil test, constituting a mere
papyraceous film, is not inconsistent with great solidity in the recent
condition, is shown by the existing Limulus, whose leathery integu-
mentis thick and hard enough to give firm attachment to very large
and powerful muscles, and yet contains so little calcareous matter,
that when dried and subjected to such pressure and decomposing
influences as have operated upon the Pterygoti, it would probably
be hardly more bulky.

It is not without interest to find that the skeleton was as perishable
in the Crustacea as in the Vertebrata of the period in which the
Pterygoti flourished.

Note, p. 28.— So long ago as 1840, Milne Edwards indicated the relations of Eurypterus
-with the Copepoda in the following -words :— " The fossil Crustacea of -which M. Dekay
has formed the genus Eurypterus appear to have much analogy with Pontia (Pontella')
and Cyclops, and also seem in gome respects to form a link between these animals and the
Isopoda"— Hist. Nat. des Crustaces, t. iii. p. 422.

BRITISH FOSSILS.

MONOGRAPH THE FIRST.

PART II. — DESCRIPTION of the SPECIES of PTERYGOTUS. — By J. W.
SALTER, F.G.S., A.L.S., Geological Survey of Great Britain.

PTERTGOTUS. GEN. Ag.

The generic characters have already been detailed in the intro-
ductory portion of this memoir. It is only necessary here to give
them in brief, and point out the two very distinct sections or sub-
genera into which the group may be divided. These sections are
indicated by the form of the head, the position and outline of the
eyes, the shape of the labrurn and palpi, and probably, too, by that
of the terminal abdominal segments.

Genus PTERYGOTUS. AGASSIZ, 1844. (Class Crustacea, Order Eurypterida.) Cara-
pace small, semi-oval or subquadrate, with lateral eyes, followed by 12 body segments
unfurnished with appendages, the twelfth being a large telson, pointed or acuminate, or
blunt and bilobed : epistoma large, deeply trilobed ; antennae of few (4) joints, strongly
chelate ; mandibles (and maxillaj ?) with palpi of 6 or more joints ; metastoma ovate, large,
notched anteriorly ; a large pair of ectognaths, their terminal joints expanded for swim-
ming, and the great foliaceous basal joint furnished with an inner serrate lobe or process.

Section 1. Carapace semi-oval, produced in front beyond the elongated lateral eyes ;
labrum with its middle lobe ovate; palpi linear, simple; bases of swimming feet
foliaceous and overlapping each other; the succeeding joints attached posteriorly.
[Terminal joint or telson truncate or bilobed ; the penultimate not expanded.] 3 species.
P. bilobus, &c.

Section 2. Pterygotus proper. Carapace quadrate or subquadrate, seldom semi-oval
or produced in front ; eyes large, round, placed far forwards ; labrum transverse, its
middle lobe sagittate at base ; palpi with tumid joints, fringed, or branched ; bases of
swimming feet not overlapping each other ; the succeeding joints attached more forward
than iu the last section. [Telson ovate, apiculate, or greatly produced, the penultimate
joint expanded.] 12 species. P. anglicus, P. gigas, &c.

It will be seen that these sub-genera contrast in nearly all points.
The production, however, of the front margin into a semicircular
form in one of the true Pterygoti, P. gigas, and the possibly
emarginate apex to the long ovate telson of that species, show that
these characters are not without variation. Yet even in this case
the large rounded eyes and wide expanded penultimate body joint

355815

38 BRITISH FOSSILS.

indicate that the species belongs to Section 2. The forward position
of the eyes is extravagantly shown in such species as P. acuminatus,
in which, too, the telson attains its greatest degree of elongation.
P. stylops has a similar but even more prominent eye.

The overlapping of the basal joints of the swimming feet in
Section 1, and the attachment of the other joints lower down,
may be characters of less importance, but they are associated in
P. bilobus and P. inornatus with the characteristic elongated eyes,
and the central lobe of the labruin is ovate, instead of sagittate
in these species. The terminal joint or telson is also of like shape
in P. bilobus and P. Banksii, the only two species of the sub-
genus in which it is known.

Although, therefore, Himantopterus has been restored to Ptery-
gotus, the character in which it was formerly supposed to differ, viz.,
the lateral eyes, being common to both, it is advisable to keep the
above two sections or subgenera distinct ; and it may hereafter be
necessary, when we have a more complete knowledge of the several
species, to reinstate the section as a genus, in which case the name
Erettopterus* will be appropriate. It is certainly more remote from
Eurypterus than is Pterygotus proper, and some unpublished species
of the former have the eyes so far outwards as to make a near
approach to the section or subgenus here described. The shape of
the antennae, however, is quite enough to separate them ; and the
telson of Eurypterus, so far as it is known, is linear,f or linear
lanceolate.

•Pterygotus is known now to range from the Upper Llandovery
Hock (or May Hill Sandstone) through all the overlying Upper
Silurian Rocks into the Cornstones of the Old Red Sandstone,
though it is but rare above the base of the last-named formation ;
its metropolis seems to be at the point of transition between the
Silurian and Devonian formations. Fifteen species are known.

Eurypterus began not quite so early, being first met with in the
Upper Ludlow Rock, and thence, becoming abundant in species
(though of small dimensions) in the passage beds at the base of the
Old Red Sandstone, attained its maximum of size in the upper
portions of that formation and the base of the carboniferous rocks,
after Pterygotus had apparently ceased to exist. (See Quart. Journ.
Geol. Soc. for 1859, vol. xv. ined.) About sixteen species are known.

* tpfTTia, for fyfWw, to row ; instead of Himantopterus^ see note p. 10.

f Styloiiurus, Page, has a similar form, but possesses thirteen body segments and long

ear swimmin feet

linear swimming feet

BRITISH FOSSILS.

PLATE I. FIGS. 1-12.

SECTION 1.
PTEEYGOTUS BILOBUS.

P. 8-uncialis, sublcevis, capite semielliptico, corpore abbreviate antice
latiori, caudd oblongd carinata emarginata.

SYNONYM. Himantopterus bilobus, SALTER, in Quart. Journ. Geol. Soc.
vol. xii. p. 29. fig. 1. ; also " Siluria," 2nd edition, p. 155, foss. 21. PAGE,
in Advanced Textbook, p. 135, fig. 1.

We have more perfect materials for this species than for any of
the rest, — above twenty specimens, many of them full grown, and
showing all the segments ; in some the head with its elongate eyes
and few-jointed antennas ; the long palpi in others ; two show the
serrated jaw feet beneath the carapace with the swimming joints
attached ; the post-oral plate is in situ in another ; and there are
numerous detached specimens of all the appendages except the
palpi, of which last we should know but little but for the ex-
planation afforded by the next described species.

The geological position of this and the other Pterygoti from
Lesmahago has been fully given by Sir R. I. Murchison, our Director-
General, in the 12th volume of the Quarterly Journal of the Geological
Society, p. 23. . The occurrence with them of a small spiral shell and
a Lingula, identical with those of the Downton Sandstones of
Shropshire, justifies the reference of the strata to the age of the
Uppermost Ludlow Rocks, while not one of the species is identical
with those of the border counties of Wales, either in the Ludlow
Rocks or in the Passage Beds which immediately overlie them.
This fact is remarkable, and may serve to indicate the probability
of a vast number of species yet to be discovered.

40 BRITISH FOSSILS.

Description. — The general form of H. bilobus is elongate-oval in
front and attenuated behind (resembling a good deal the outline of
a Palcconiscus or other fish). The thorax is not easily distinguished
from the abdomen, into which it is attenuated, the greatest width
being about the third or fourth segment ; its segments are widely
transverse, those of the abdomen become less and less so, till the
last but one is nearly square ; the tail joint is oblong and emargi-
nate and narrowest of all ; the antennae are slender and long, the
swimming feet narrow, the palpi filiform ; and these general cha-
racters, taken together with the small size (seldom nine inches,
long), will easily distinguish the present species from the following.
The different portions may now be more minutely noticed.

The carapace, one inch and a quarter in length, is half oval, only
one-fifth wider than long. The position of the long eyes is very
forward on the sides, and they somewhat interrupt the general oval
contour. They are broadly crescentic and convex, placed half
below (fig. 4 c) and half above the margin of the head, and their
extreme length is rather more than half that of the head. No
lenses can be seen with the naked eye, but when magnified the
appearance is that given in fig. 4 d.

Body Segments. — The body in well-preserved individuals is
barrel-shaped in front, the anterior or thoracic segments, taken
together, measuring about one inch and three quarters in length
by one inch and a quarter broad. They are widely transverse, the
anterior one being fully four times as broad as long, or even more.

The second ring, as seen in a specimen not here figured, is five
times as wide as it is long, the central part gently arched forwards
in the middle, and at the sides the upper angles are produced for-
ward into blunt lobes,* the outer margins being oblique, and their
posterior angles are a little produced backward, particularly in the
sixth or hindermost thoracic ring.

The remainder, which are here reckoned as abdominal, are gra-
dually narrower, the seventh being only three times as wide as long,
the tenth only once and a half, and somewhat narrower at the origin
than the posterior edge ; the penultimate^ (eleventh) is squareish,
only a little wider than long, also contracted at the origin and with
the outer angles produced to lap over the rounded anterior edges of
the caudal joint. A strong carina runs down this segment upon
the upper side, but for the lower half only.

* This form of the second segment is common to all the species, see fig. 13 of this
Plate, and Plates IV., X., XIII., &c.

BRITISH FOSSILS. 41

The caudal joint (telson) is only two-thirds as wide as long, and
nearly double the length of the penultimate one. It is rather wider
behind, and strongly emarginate ; a deep furrow takes its origin,
from the notch, and continues more than half way up. There
is a low keel at the upper end joining that of the preceding segment,
but only for a very short distance.

The outer margins of the body and tail segments appear to be
quite smooth, not serrate or crenate as in several other species.

The thickness or rotundity of the joints we have no means of
ascertaining.

The sculpture is minute and characteristic, but is only visible at
a few points. None has been observed on the head. On the body
joints numerous small semicircular plicae (fig. 2 a) — the curve open
forwards — cover the surface, but are less conspicuous on the hinder
portions of each segment. On the anterior narrow segment they
are perhaps most prominent, and on this and some other of the
front rings a raised transverse thread-like ridge runs across at
about the middle, or a little in advance of it, but does not limit
the conspicuous portion of the sculpture.

Under Side of Head, and Appendages.

In three or four specimens, figs. 1, 3, 4, 9, &c. the organs of the
mouth, with the antennae, are in situ, and in others the appen-
dages of the head occur so grouped together as to show that they
were associated. Fig. 3 appears to have the parts most complete.

Antennae (fig. 6, &c.) — None have been found more than two
inches long by a quarter of an inch broad at the base of the chelae,
the free joint of which is, in antennae of this size, about six-tenths of
an inch long. The base of the fixed finger is but slender, scarcely
thicker than the preceding joint, and is shorter than the chelre, the
shafts of which are linear and straight. (Fig. 7 is broader than usual,
and may indicate a difference of sex.) The points of the chelae
are sharply incurved ; their armature is minute, of small and larger
teeth.

There are apparently but four joints in the antennae, the basal
one small, the second, fig. 7 6 (both figs. 6 and 7 are wrongly drawn
as to the length of the lower joints, from being so much broken), at
least five times as long as broad, the fourth (c) is the fixed claw
and its base, and the fifth the free claw. The articulations of the
joints are all oblique.

42 BRITISH FOSSILS.

Endognaths (Mandibles, &c.}— The under side of the carapace, of
which fig. 4. is the cast, shows the great foliaceous bases (with serrate
inner lobes) of the swimming feet (c). No mandibles or maxillse*
have been discovered beneath these ; but in fig. 1, at c, the long-
filiform palpi of one pair of these organs extend right and left
of the carapace. They are more elongate than in other species.

A small mandible, found since the plate was engraved, is here
oiven as a woodcut. It is contracted in width as compared with

|pi|||iy ^%, r p, the basal or attached portion ;
Endognath (Mandible), natural Z, HP ^ ?

size ? of Pterygotus bilobus. ^ - C~3' pa

the shape in some other species. The anterior serrate lobe a is
narrow, and with sharp curved articulated teeth. The lamina p is
oblique and sub-triangular ; and the palpus, set on rather far back
from the serrate border, has a small quadrate basal lobe c followed
by a longer one d; the third and fourth (ef) are linear, and
several times as long as broad. The terminal joints are still
longer, as seen in Plate I. fig. 1 c (compare this with Plate VII.
figs. 4, 5.)

Epistoma and Labrum. — Of the large semicircular piece which lies
in front of fig. 1, and which has evidently been shifted from the under
side of the head, we can only judge the true position by comparing
it with other species (H. perornatus, for instance, fig. 16, in which
the mid-lobe a of the organ is seen to be of an ovate shape) ;
also in Plate XV. fig. 2 /, where a similar piece lies in front of
the head.

In fig. 1 the semicircular outline probably corresponds to the
hinder free margin (of much more angular shape) in the epistoma of
P. anglicus, Plate III. The mid lobe a is obscurely marked out,
but is of an ovate shape ; its insertion not very clearly seen.

Ectognaths. — Fig. 3 shows these organs in their place at the
lower angle of the carapace, drawn forward as for a stroke ; the
forward bend of the limb at the fifth joint ca, and the great serrate
bases b indistinctly visible through the crust. Fig. 9, with part of
the carapace broken away, has both lirnbs in place, and figs. 1 and 2
show these natatorial feet laid backward close along the body.

* The dilated bases of the swimming feet (ectognaths) -were formerly supposed
to be the mandibles, and the produced neck-like portion to be jointed ; Quart. Journ.
Geol. Soc. 1. c. This has been set right by Professor Huxley (see Part I.)

BRITISH FOSSILS. 43

Tig. 8, magnified at 8 a, is an entire separate ectognath. The
several joints of this appendage are : —

Basal Joint (coxognafhite), figs. 4 c, 8 co. — The great lower lobe
is wide, and of a spherico-triangular shape, the inner margins as
well as the outer and base, being all convex. The neck is sud-
denly contracted and short, and the serrate terminal lobe trans-
verse or oblong, greatly oblique and overlapping the opposite edge
(not vertical as in P. acuminatus, Plate II.) Its toothed margin
is curved and set with thirteen small teeth.

The other joints are attached low down, i.e. below the outer
margin of the basal joint, and consist of —

b. (Basignathite) short and broad-linear.

i. (Isckygnathite) narrow triangular, produced a little at the
hinder angle (but not forming a lobe as in Plate VI., fig. 1.)

m. (Merognathite) rudely trigonal, its hinder base meeting the
produced articular" lobe of the large penultimate joint p.
[Either this or the next joint ca bears the long three
jointed filament t. The forward salient angle of the
limb is formed between this and the succeeding joint.]

ca. (Carpognathite) triangular ; its convex base outwards, its
apex inwards against the process of p.

p. (PrognatJiite.^) All the preceding joints, except the great basal
one, do not quite equal the length of the penultimate joint p.
It is oblong, but narrower at the base, which is oblique, with
the hinder edge produced into a process (s), which reaches
the fourth joint (771). The outer margin is rather convex,
the inner a little concave, and the apex deeply and pretty
equally bilobed, to receive the terminal joint.

d. (Dactylognaihite?) A regularly ovate palette, as long, measured
along the middle line, as the penultimate joint, and nearly
as broad ; it is attached to it by a prominent tubercle.

No sculpture has been observed on the limbs.

Metastoma or Post-oral plate, figs. 1, 10. — These cordate plates
(referred to the posterior margin of the mouth, p. 16) occur with all
the species. The piece is nearly of the same narrow ovate shape in
this as in P. perornatus, fig. 15, but only one-third the size,
deeply cordate, with a sharp notch and rounded lobes in front, and
with the base also rounded ; the width is about half the length,
the lobes are covered thickly with rather large semi-circular plicae,
which are absent from the other parts of the plate.

44 BRITISH FOSSILS.

Fig. 1 shows this plate in its natural position, and fig. 10 a
detached plate as commonly found. The latter occurs in a group
with a pair of antenna?, of which fig. 6 is one, and with the swimming
foot, fig. 8 ; all probably therefore belong to the same individual.

Our specimens are so much altered in shape by pressure, that it is
difficult to point out any real variations in form. Fig. 2 appears
to have the true general shape. Fig. 1 is evidently compressed
laterally, as is the caudal joint, fig. 11 ; while fig. 12 shows that
joint shortened by pressure from behind forwards. Fig. 4 is
reduced in length by the same cause, and appears too broad in
proportion for the length.

Locality. — UPPERMOST LUDLOW BEDS, Lesmahago, Lanarkshire,
with several other species, and the shells Platysckisnia (Trochus)
helicites and Lingula cornea. All in the Museum of Practical
Geology. Collected by Mr. Robert Slimon.

BRITISH FOSSILS.

PLATE I. FIGS. 13-15 (AND 16, VARIETY) ;
PLATE XV. FIG. 2.

P. PEKOBNATUS.

P. pedalis et ultra, undique squamulis minutis ornatus, capite semi-ovali,
fhorace segmentis latis curvatis, oculis anticis minoribus granulatis.

SYNONYM. H. perornafus. SALTEK, in Quart. Geol. Journal, vol. xii.
p. 31, and 28, fig. 6.

One of the most distinct and well-marked species, and clearly
belonging to the same section with H. bilobus, while it is more than
double its length and width, the largest specimen being three inches
and a half wide and probably not less than fifteen inches in
length. We have the head and six body segments ; the swimming
feet, both attached and free ; maxillse with palpi, the post-oral plate
in situ, with some faint traces of antennae ; but all these show good
characters.

The head (carapace*) was formerly described by me as smooth, but
in better specimens it is closely and fully sculptured, the plicas convex
forwards. It is half a broad oval (fig. 13), three inches in length
by three inches in breadth, and the posterior angles are acute.

The eyes are forward and rather small, not extending over a
space more than two-fifths the length of the head (in H. bilobus
they are much more than half), and finely granulated, the lenses
visible to the naked eye (fig. 13).

The body segments are broader from front to back than in the
last species, the front ones particularly, but, if fig. 16 be the same
species, vary considerably in this respect. They are much arched
forwards over the wide central portion, the ends are recurved as
usual, and at less than one-third from the middle (6) a kind of fulcrum
exists, dividing the compressed lateral area (pleura) from the more

* I take leave to use in description the term " head " for convenience' sake ; carapace
is of course more correct.

46 BRITISH FOSSILS.

convex central portions. The first segment is much more rounded
off at its hinder angles c than the remainder, and the space thus
left filled by a projecting process of the second segment (see also
Plate IV.) There is a similar but smaller process to the first joint,
at least in the var. plicatissimus, fig. 1 6, and it is probably so
in all species.

The sculpture in the body rings, fig. 13 a, extends over less than
half their surface. The plicae are open forwards, very small, almost
linear on the front margin (the extreme margin of all the segments
is rounded off and smooth) and the remainder are less than semi-
circles or they are subangular (more than 90°). On each side at 6
they are not as wide. A transverse impressed line separates the
anterior sculptured half from the posteripr smooth portion, but this
is not always present. No crenate edge has yet been observed.

Appendages, Plate XV. fig. 2.

On a specimen much distorted, and from which the swimming
foot, Plate I. fig. 13*, is taken, the following organs maybe detected
by careful examination : —

Epistoma, /, reflected from the under side.

Antennae, 6, b'.

Great post-oral plate or metastoma, g.

Two endognaths, c, c, with palpi x.

Endognath (mandible or maxilla) of the opposite side, c".

A separate jointed palpus.

Ectognath (swimming foot), e, attached to the carapace.

First body joint.

/. The large epistomian plate resembles much in shape that seen
in Plate I. fig. 1 a, which is similarly displaced. We only see a
portion of it, the termination being broken off, but it appears to have
been semicircular and semioval, more than three-fourths the width
of the carapace, and covered with minute prominent plicas. Near
its base, but not attached, are remains of a single antenna, b.

b, b', Antenna. — Only the general form can be made out; it is
thick in proportion to the size of the specimen, and consists of
apparently only three joints, the lower one broken (6), the frag-
ment three times as long as wide ; the second (&'), crossed by a line,
which is probably a fracture, appears to be a long single joint, five
times as wide as long, its articulation with the neighbouring joints
being marked by small irregular crenulations. The penultimate
joint or fixed finger b" is much crushed, it seems to be contracted

BRITISH FOSSILS. 4,7

at its base, the lower part barrel shaped, about twice as wide as
long, and tapering rather gradually into the serrate portion. The
free claw V" is broad, linear, and beset with numerous small teeth,
a few larger striated ones interspersed ; the first only is seen on each
chela, that on the fixed claw very near the angle ; that on the free
finger is more distant.*

c', c", Mandibles, &c.f — There are traces of two pairs of jaws, the
palpi attached or in close proximity, figured with the rest of the
carapace in Plate XV. fig. 2. One endognath is lying loose on the
left hand of that figure in a reversed position, and has the usual
curved striate teeth, but nothing can be determined of its shape.
On the opposite side two jaws with palps lie one over the other,
and a woodcut is added below, Fig. 2, to show in a diagrammatic
form the arrangement of these pieces with their appendages.

The outer jaw, g, shows the terminal serrate lobe, with at least
seven articulated arched teeth (the uppermost largest), and about

FlG- 2' * e ll This specimen is

Pterygotus pcror- A ^MRnRnin&^dHfeild^^ FA the same as that

- . , M figured in Plate

bles,0, A; palpi, . ••''Y^^^f:^ ll XV. fig. 2, but

c, h,i, &c. The '&£'' '^'~ ^^^\ with some parts

post-oral plate is ^^^r^ ' ^fef; - ' ^ omitted.

in situ. ,\7

three times as long as the breadth at their base, and sharp pointed.
The other, k, is pushed in advance of g; it shows a similar set, more
displayed, of curved striate teeth ; about five are distinctly preserved.
The filament c, I, which, from analogy with that of H. bilobus, is
presumed to be the palpus, appears to me to be connected with the
mandibular piece g, and to cross the two others, h, i, which seem to
form part of a branched palpus, and to belong to a second ectognath
(mandible or maxilla). But the connexion of these with the serrated
pieces g or k is not quite certain ; they must therefore be described

* In Pterygotus the large teeth are very nearly opposite one another in the middle and
outer portions of the forceps, and must have acted as cutting blades, not merely as
prehensile forceps (see Plate VI.)

f Discovered in this species by Professor Huxley. But he does not agree with me, that
there is sufficient evidence of the two pairs of jaws, one with a single, the other with a
branched palpus (see p. 23).

48 BRITISH FOSSILS.

provisionally as belonging to them. The filament c, I, consists of at
least four elongate sublinear joints, besides a basal one, or probably
two, which are short and obscure. The first of the long joints is
rather swelled and crenulate or spinose at the tip (at*) ; the next,
which is about four times as long as broad, shows some little
crenulation.

Of the branched filament (or pair of filaments) h, i, the junction
with the maxilla is quite obscure ; there are about three linear joints
to each, broader than those of the palpus c, L The detached fragment
m, if it belong to this specimen at all, would from its size correspond
to one of this pair (h, for instance, rather than V).

5. Swimming Feet, Plate I. figs. 13*, 14.— Fig. 13* is found at-
tached to the carapace, above described, which has the maxillae and
palpi, &c. attached. Fig. 14 lies loose in the same slab, and as it is
materially different from that of the other large Lanarkshire species
(P. acuminatus, Plate II.), belongs, no doubt, to this. The basal
joint (fig. 14) is less expanded in the lower part than in H. bilobus.
It is rudely trigonal, the sides convex but not equal, the forward edge
(14 a) being shortest, and the lower angle d produced. The neck
is rather broad, and the terminal lobe linear-oblong, with a straight
serrate edge. The teeth are fourteen, besides the small lower lobe
b, short and conical, and very obliquely set. The surface is closely
plicate (fig. 14 a) nearly all over.

The other joints, fig. 13*, are very obscure, but constitute a linear
swimming paddle, but little bent, like that of H. bilobus. The second
joint is lost, but the third (i) is linear, the fourth (m) triangular,
and the fifth (ca) irregular and obscure in the specimen. The
penultimate joint and terminal palette (p, d) are much distorted ;
but in a fine specimen of the carapace, with the swimming feet
(ectognaths) attached, and which was discovered by Mr. Slimon
since the plates were finished, the penultimate joint (p) is more
than twice as wide as long, with a strong process from its hinder
angle running upwards, and a deeply notched termination to
receive the terminal oval palette. This last is short and narrow, com-
pared with that of P. bilobus. (See woodcut, fig. 3.) The two ecto-
gnaths are very perfect ; they are attached at the outer angle, but
turned outwards in this specimen by decomposition of the attaching
muscles, so that the exterior margins are placed opposite to each
other, and the inner serrated lobes look outwards (the dotted lines

BRITISH FOSSILS.

49

show what was their original position).
is distinctly shown in this specimen.

The shape of the carapace

FIG. 3.

U

P. perornatus, carapace, and swimming feet ; one-third natural size.

Locality. — Lesmahago, Lanarkshire, with the last. Besides the
Pterygotus acuminatus, Plate II., this is the only large species
which occurs in the locality. It is not common. Mus. Pract.
Geology. Collected by Mr. R. Slimon.

P. perornatus, Yar. plicatissimus, Plate I. fig. 1 6.

This, which differs materially in the breadth of the segments, and
somewhat also in the manner of sculpture, must be regarded, till
more specimens are obtained, only as a variety. But it will very
probably be found a distinct species, in which case it is only
necessary to use the varietal name as a specific one.

The carapace (in fig. 1 6) is much compressed longitudinally, but

the true form would probably be a full semioval, as in the preceding
woodcut ; the position of the eyes is obscurely marked. The sur-

[1.] D

50 BRITISH FOSSILS.

face is covered with semicircular plicae, the curves of which open
backwards (contrary to the usual position over the rest of the body).

In front is seen the impression of the large ovate median lobe (a)
of the epistoma, shaped as usual, and behind are two radiated mus-
cular impressions (6) placed low down on the carapace, and towards
the median line, which impressions are probably the attachments
of the great swimming feet.

We have only space to figure one of the seven body segments :
the anterior six are probably thoracic, the last of these having a
large projecting hinder angle which overlaps the base of the seventh
(or first abdominal) segment. All the segments are conspicuously
broader in proportion than in H. perornatus, the second, third, fourth
fifth, instead of nearly five times as wide as long, being not above
three and a half times, and this difference is remarkable in the front
segment (c), which in H. perornatus is very transverse, seven times as
broad as long, but in this is only four times and three-quarters as wide.
It has very distinct anterior lobes, like those of the second segment.

The sculpture of the rings differs from that of P. perornatus in
having the plicae narrower and longer, the angular ones being less
than 90°, and even on the anterior margin they are not less than
semicircular.

Each segment except the first is crossed by a very distinct
impressed line, which bisects the anterior sculptured half, and is placed
in the second segment at the anterior third (in the first segment it
is absent), the rest have it very near the anterior margin.

The seventh segment is two and a half times as broad as long,
and has square, not produced posterior angles.

Locality. — Lesmahago. Mus. Pract. Geology. (Collected by Mr.
R Slimon.)

BRITISH FOSSILS.

PLATE XII. FIGS. 22-46.

PTERYGOTUS BANKSII.

P. parvulus, 4-5 uncialis, capite convexo, semiovali, vel parabolico,
ad frontem subangulato, oculis brevibus gibbis, ad dimidium capitis :
annulis trunci omnibus transversis, cauda expansa truncata biloba.

SYNONYM. Himantopterus Banksii, SALTER, Quart. Journ. Geol. Soc.
vol. vii. p. 32, also p. 99. and pi. 2. fig. 5. [fig. 6, is the caudal joint of an
Eurypterus]. Siluria, 2nd ed. p. 266. foss. 66. fig. 1.

Named in honour of Richard Banks, Esq., of Kington, Hereford-
shire, who has made rich collections of the Pterygoti of that locality,
and has generously relinquished the publication of his materials in
our favour. He has also presented to the Museum all his accurately
coloured drawings and notes.

" This small neat species, of which we have many specimens in
the Museum of Practical Geology, occurs with Pterygotus (P. gigas,
Plate VIII.), and spines both of Crustacea and fish, in the yellow
tilestone (Downton Sandstone) beds of Kington, Herefordshire. It
is there associated with the Platyschisma helicites and Lingula
cornea, Sil. Syst. These are the two species of shells which accom-
pany the fossils of Lesmahago above described, a good argument,
therefore, even without other evidence, for regarding these Lesma-
hago beds as the uppermost portions of the Ludlow rock." — Quart.
Oeol. Journ. I. c.

Description. — The full size must have been from four to five inches
long, but the specimens usually met with would probably not be
above three or four inches. One or two show the connexion of the
body rings with the head and appendages, fig. 42, or with the tail
joint (fig. 23). None are quite complete, and though we have nearly
all the parts, they are usually disjointed.

The carapace (fig. 22) is a broad semioval, its length as six to
seven, except when lengthened or shortened by pressure (figs. 25, 26).
It is regularly convex, a little angulated in front, smooth, and bears
the small oval eyes rather more than half-way up the head. They

52 BRITISH FOSSILS.

are much smaller than in H. bilobus, being not above one-fourth the
length of the carapace, and very convex.

The body is at first wider than the head and then tapers back-
wards. The first ring is very narrow (fig. 42), the second twice as
broad and with the usual dilated extremities ; the third, fourth, and
fifth strap-shaped, arched in the middle and direct on the sides so
that the segment appears much bent. The ends are truncate, in the
anterior rings widest behind, and in the posterior ones tapering
backwards.

Fig. 28 shows one of the hindermost rings, such as are seen in the
more complete specimen, fig. 23. The hinder rings become gradually
less transverse, the tenth only two and a half times wider than long,
and the penultimate about once and three-quarters its own length.

The caudal joint (telson) figs. 23, 38, 45, differs, in its expanded
form, materially from that of H. bilobus. It is about three-fourths
as long as wide, narrow at the base with two short ridges running
down from either angle ; then expanded with somewhat convex
sides towards the wide subtruncate apex ; the outer angles are
rounded off, the terminal notch shallow, and a short median keel
continued from it one-third up the segment.

The sculpture of the head is not known. On the body rings a
transverse lineation running into open plicae on the sides (fig. 43 a)
occupies the front margin for not quite half the segment ; a few
plicse are intermixed with the lines.

[On the caudal joint, fig. 46, a lineation, parallel to the outer
border (a) is distinct, but it is uncertain if this specimen be of the
same species ; it has a strong median groove down the under side,
and is less expanded in form than P. Banksiii]

The swimming foot, fig. 42, has a characteristic shape, the upper
joints (fourth and fifth) are rather narrow, and the penultimate (p),
instead of being simply conical as in H. bilobus, is ovate (more so
than in our figure), with the outer border especially convex. It is
notched above to receive the fifth joint, and below divided into very
unequal lobes. The terminal palette d is true oval, rather blunt
at its origin and more pointed at the extremity. It is nearly equal
to the penultimate joint in length, but considerably narrower.

Fig. 35 is a penultimate joint, probably of the same species.

Antennce. — Figs. 30 and 40 are presumed to belong to this species,
as they occur with them. They are remarkably slender and straight ;
the base is large and broad, suddenly attenuated into the shaft,
which is only a tenth of an inch wide, and three-quarters of an inch
long, beset with close small teeth, and furnished with three larger

BRITISH FOSSILS. 53

conical ones nearly straight, the central one as long as the width of
the shaft. In fig. 40, from the Ludlow Rock, the intermediate teeth
are a little longer in proportion.

The basal joints, fig. 29, are flask-shaped, much more elongate
in the neck than those of H. bilobus, and less swelled at the base.
[It is possible they may not belong to the species at all, but to
Eurypterus linearis, a species which occurs in the same beds ; we
do not yet know this joint in Eurypterus.] The base is subqua-
drate, quite rectangular on the outer upper margin : — the notch
for attachment of the other joints is immediately beneath this
angle, — and tapering into the long neck, which has a sharp ridge
posteriorly, and together with the terminal lobe equals the length
of the basal portion. The teeth are minute.

The post-oral plates, figs. 31 to 34, differ a little in shape from
figs. 41 to 44, but not specifically, unless the greater amount of
ornament in fig. 41 may be considered sufficient to separate it. The
shape is elongate oval, the greatest width at the upper third, the
base (6) subtruncate, the apex with a shallow obtuse notch. At
the lower fourth (a) is evidently a tubercle of attachment, and
such as occurs in a more linear shape in other species, Plate II.
fig. 4 a. [It is desirable to find out the post-oral plate of Euryp-
terus ; which is probably very similar.]

The sculpture is very conspicuous over the upper half ; it consists
of nearly straight or very slightly curved plicae arranged in arched
lines and ending abruptly against the outer margin. In the sand-
stone specimens the sculpture does not extend so far down, but it is
identical in structure.

Localities.— UPPER LUDLOW ROCK, Ludlow Lane, Whitcliffe
(and Batchcot ? fig. 46) ; Parian, exterior slope of the Woolhope
"V7 alley (Mus. P. G.) ; Kington, Herefordshire (Mr. R. Banks' cabinet).
PASSAGE-BEDS, Ludlow Railway cutting (Cabinets of Messrs. Light-
body and Marston, at Ludlow ; Museum Pract. Geol.), &Tc.

BRITISH FOSSILS.

PLATE XII. FIG. 47.

P. STILOPS.

P. parvulus, capite (parte antica solum asservata) 9 lineas lato, convexo,
quadrato, fronte {fraclo) producto ? lateribus rectis ; oculis ad angulos
externos fixis, magnis, turgidis.

This remarkable small carapace, the anterior part of which only
is preserved, has occurred to the assiduous search of Mr. R. Banks
of Kington.

Only the anterior part is preserved, and even of this the frontal
portion between the eyes is broken off; it was perhaps less promi-
nent than the dotted lines indicate. The forward position and round
form of the great eyes very much assimilate the species to P. acu-
minatus, and without doubt it belongs to the same section, or the
true Pterygotus.

The eyes are remarkably prominent and turgid, a slightly raised
fold of the carapace encircling them. A small tubercle, like that on
the same part in P. gigas, Plate XII., occurs on the median line of
the head, and rather nearer to each eye than their distance from one
another. As only a single broken specimen has occurred it is useless
to describe it further. There can be no doubt of the distinctness of
the species.

Locality. — Kington. Coll. Mr. R. Banks, of Kington.

BRITISH FOSSILS.

PLATE II. ; ALSO PLATE XIII. FIGS. 1-4 ; PLATE XV.
FIG. 1.

SECTION 2. — PTERYGOTUS.

PTERYGOTTJS ACUMINATUS.

P. magnus, 3-pedalis, elongatissimus, capite oblongo angulis quadratis,
oculis rotundis minoribus: segmentis corporis 12, quorum quinque anticis
transversis bicarinatis, reliquis subquadratis, penultimo oblongo; cauda
ovata in apiculum longum producta.

SYNONYMS. P. acuminatus, SALTER, Quart. Geol. Journal, 1855,
vol. xii. p. 29. fig. 4. P. maximus, id. p. 28. fig. 3. Slimonia (1856),
D. PAGE, Advanced Text-Book, p. 135. fig. 3.

That the two figures above referred to belong to one and the
same species is, I think, almost certain, and all the fragments in our
Plate II., &c., occur in juxtaposition, and are doubtless remains of
the same large Pterygotus, the finest of the four or five species
which were collected from Lesmahago by Mr. R. Slimon. Although
not so gigantic as those next to be described, P. acuminatus is
yet a very large species, and more elongated in all its parts than
any of the others. The head is nearly five inches broad and six and
a half long, and the seven hinder or abdominal rings, which are
different in shape from the anterior thoracic ones, are almost square
instead of transverse ; while the tail is ovate anteriorly, and behind
is drawn out into an apiculus equalling the anterior portion in
length.

The Head, Plate II. fig. 1., is oblong, with straight sides, except at
about the anterior third, where it is contracted so as to give it a
suburceolate shape ; the front is somewhat rounded, and as well as
the sides crenated, or rather tuberculated along the edge ; the eyes
are placed at the anterior angles, as forward as in P. anglicus, but
much smaller in proportion, oval, about six-tenths of an inch long,
and very prominent.

Of the body rings, which are twelve in number, including the
tail joint (telson), we have several good specimens. Of these the chief

58 BRITISH FOSSILS.

are figs. 10 and 11 in Plate II. The former is of the natural size,
a young specimen, showing the whole of the body rings ; the two
hinder ones are left out for want of room in the plate, but these are-
well seen in fig. 11. The rings are arched, and were probably
very convex, and both the front and back edges of the segments can
be seen in our compressed specimen ; the former as a segment of a
circle, the latter as its chord.

The lateral hinder edges of at least some of the segments are
produced (fig. 1 Qg) into short processes, and their margins are acute.

Six segments appear to be thoracic, and are more transverse
than the hinder ones, about three times as wide as long (the front
ones still wider), and each is marked at its hinder extremity by
two short keels* along the median space, not much raised above
the surface, and about a quarter of an inch long. The hinder
abdominal segments, of which fig. 10^ is the first, are destitute of
these median keels, and gradually longer in proportion to their
breadth till the tail-joint is reached. The first segment (a) is only
three-quarters of an inch long by one and three-quarters broad ; the
second and third (6, c) are much narrower, about nine-tenths long.
The fourth measures more than an inch in length ; the fifth one inch
and a quarter, but rather less in breadth, and narrowed posteriorly.
It is destitute of any central ridge or keel above or below. The
tail segment (telson) in this species is a large oval plate, terminated
by a long apiculus ; the length without the apiculus is two inches
and a half, and with it four inches ; the breadth is nearly one inch
and three-quarters, narrowing to the base, which is thickened,
(probably cylindrical,) the rest being much depressed. On the
upper surface a strong carina arises near the origin of the joint,
and continues to the tip of the apiculus. The lower side is flat-
tened, or but gently convex at the base. The margin of this tail
joint is closely serrate or tuberculate in a double line near the base
(like that of the margin of the head), running into a single line of
distant long tubercles below and along the apiculus.

This kind of double tuberculate border is conspicuous down the
sides of the head, the tubercles being elongated, while on the
arched front border there are three or four rows.

The ornamentation of the body rings is quite minute, and is
but rarely seen in our specimens. It is confined to the anterior
border of the segments ; the plicae are small, equal, and rather
prominent.

* The first pair is seen in fig. 10, pushed back over the second, and is the best indi-
cation of the boundary of the segment a.

BRITISH FOSSILS. 59

Appendages.

Antennce, Plate II. figs. 2, 3. — The position of these serrated
organs is settled by their mode of occurrence in the species previously
described. The fragments, figs. 2, 3, being the largest chelae in the
stratum, and, occurring also with this large species, probably belong
to it. The teeth are narrow, lanceolate, shorter than the width of
the shaft, turned a little backward, and closely striate. The three
primaries are rather more than their own length apart, and the
last rather more remote from the terminal tooth, which is curved
upwards nearly at a right angle. The secondary teeth are sharp-
conical, and five or six in each interspace. The shaft is rather
broad, its outer edge quite straight, and at the tip, which is blunt
and abrupt, strongly punctured for a short distance. The free
claw, fig. 2, has the usual contraction at its base.

Oral Appendages. — From a number of fine specimens from
Lesmahago, found since the plates were engraved, some excellent
additions have been made to this species ; these will be given in
woodcuts. They render, I think, unnecessary some of the argu-
ments used further on to prove the existence of two pairs of jaws
with their palpi, but as those refer to the evidence as it stands in
the plates, it is thought better to retain them.

Epistoma, and labrum. — A piece answering to the shape of this
organ in another species (see Plate III. figs. 2, 5), and of size
suitable to that of P. acuminatus, occurs with it at Lesmahago.
It is specifically different in the great length of the central lobe (6),
which projects forward a long way beyond the side lobes or wings ;
or we may consider these latter as contracted (a). The whole piece
is transverse, instead of rudely triangular, and the sculpture con-
fined to the anterior border. The median lobe (6) is pyramidal,
not sagittate, at the base ; its tip is broken off.

Half the natural
size.

The occurrence of this more perfect specimen renders it un-
necessary to suppose that Plate XV. fig. 3, should represent the

60 BEITISH FOSSILS.

central lobe of this organ. Nevertheless, it has the expanded
sagittate base usual in this section of the genus, and from this
base extends a narrow lanceolate piece, ridged along the centre,
and shelving (to pass under the lateral lobes) on the sides. These
contract near the tip, which is again expanded a little and then
forms a cordate pointed lobe. The piece is one inch and three-
quarters long, and half an inch wide at its broadest part (below
the middle). I do not know to what species it can be referred.

There is yet a third and very large plate found in the same
stratum, which, from its shape and structure, appears likely to
belong to an allied species, and differs from both the above described.
A woodcut (fig. 6) is here given of it, half the natural length. It
is keeled along the middle, and rounded near the tip.

PIG. 6.

Portion of Epis-
toma.

Post-oral Plate (Metastoma), Plate II. fig. 4. — This plate is seen
in situ (Plate XV. fig. 1, g\ and sometimes occurs of large size,
above three inches long. The form is broad-linear above, then
contracted at the lower fourth to half the width ; this lower por-
tion also has parallel sides, is rounded below, and furnished with
a strong central keel, which is probably the line of its attachment
to the head. The upper end is deeply bilobed, the lobes elliptical,
and the notch very narrow ; except the raised keel along the
hinder portion the entire plate is flat, the upper portion marked
with large and rather obscure semicircular plicse, which are seen
occasionally scattered over ull the plate. The elongated form of
this organ, compared with that of the preceding species, corre-
sponds with the longer shape of the head ; and it may, perhaps,
guide in determining what the form of the carapace of other
species was, where only the metastoma is preserved (as in P. punc-
tatus, Plates VIII., IX.)

EndognatJia (Mandibles, &c), Plate XIII. figs. 1-4, Plate XV.
fig. 1). — These were omitted by accident from Plate II., but are
very important for understanding the structure of Pterygotus, since
they appear to indicate that the animal possessed two pairs of

BRITISH FOSSILS. 61

masticating organs (exclusive of the serrate bases of the swimming
feet) as before indicated for P. perornatus.

Fig. 1 in Plate XIII. occurs with the fragments of the species,
and probably belongs to it, as its form is so elongated or compressed
laterally (compared with those figured on Plate VII., which belong
to a broad-headed species). The length from the serrate edge a b,
to the end of the basal process /, is no greater than the breadth of
the serrate margin a b. The general form is broad-falcate, the pro-
duced base / squareish, and the insertion of the palpus c very near
the serrate margin. This is beset with curved narrow teeth, six or
seven of which are distinct in the upper half, and there are numerous
smaller ones below. The teeth are articulated with the margin,
not mere processes of it, as in the serrate base of the ectognath.

Figs. 2, 3, 4, however, belong certainly* to P. acuminatus.
Fig. 3 shows the endognath a, seen only in part, with a simple
palpus attached c d, of which only two joints are preserved ; the
lowest c broad and almost urceolate (not shortened, as in Plate VII.
fig. 9), and about as long as wide. The second d is narrower; minute
plicse cover the base of both joints. Beneath this, and apparently
attached to a distinct plate e, pressed closely upon a, and sculp-
tured like it, is another and broader palp, of which only the basal
joint is visible ; and we must refer to a more perfect specimen
(fig. 2, 2 a) for other details of this appendage.

In fig. 2 the endognath a is seen to have a straight edge above,
with which the serrate margin forms an obtuse angle (about 120°).
It is rather suddenly contracted where the teeth begin ; they are
very oblique, narrow, conical, with a rounded base, and straighter
than those of the separate specimen, fig. 1 (the latter is, however,
as before said, probably the same species).

The first two joints of the single palpus c d are quite distinct,
and c in fig. 2 a shows a toothed distal edge, such as is seen in the
joints of fig. 4. The second palpus (probably attached to the crushed
second maxillary piece) shows obscurely three or perhaps four
broad joints at base, / g, and then divides into a pair of jointed
styles h i k I, with tubercular or spinose joints.

Fig. 4 explains this second appendage, it has a broken and
obscure basal portion a (which may be part of the serrate basal
joint ?) followed by three broad joints bed, the second (&), being

* As Prof. Huxley has described Plate XV. fig. 1, in detail, I need only refer to it
here (see p. 22.) It shows, I think, the single and branched palpi; but only one
mandibular piece, -with teeth, is visible on each side.

62 BRITISH FOSSILS.

transverse, c and d are nearly square, thickened at their ends,
which are ornamented by a crest of spiniferous tubercles. Similar
tubercles occur scattered over the surface, and particularly on the
outer edges and down the middle. They are also in parts orna-
mented with minute plicae parallel to their length. It is not quite
certain if c and d are single joints, or two styles parallel to one
another and pressed closely together, d is probably a pair of joints,
as besides the crested spiny edge, it is furnished with a pair of thick
curved spines (like those of the succeeding joints) on each half.
efgin. the longer filament are of less diameter, successively shorter,
but still thickened at their ends, and furnished with thick curved
spines three or four in number ; the terminal joint Ti, I, in both fila-
ments is a strong simple curved spine, without a striated surface or
any serrations to the border. These terminal joints are not well
' seen in the large specimen figured in PlateXI V., but the proximal
joints are more perfect.

The position given to the palpus in this plate, XIII., with the
spiny crests directed forwards, is in conformity with the position of
the much larger spines in P. punctatus, fig. 9.

It is difficult to prove the existence of two separate maxillary
pieces from any of these specimens (Plate XIII. fig. 2, affording the
best evidence on this point). But it seems pretty clear that there
were two palpi on each side, one simple, the other branched from
near its base : — the number of joints before branching cannot be
stated with certainty. If only two filaments be admitted on each
side, the alternatives will be — a single mandible with a branched
palpus, — or two mandibles each with a simple palpus. We have

fortunately met lately with a specimen (fig. 7), tolerably perfect,.
and showing the basal serrate joint, with six simple joints follow-
ing ; the terminal uncinus is lost. There must, therefore, be two
jaws, one of which has a simple palp : the other most probably a
branched one.

BRITISH FOSSILS.

Lastly, we have a very perfect head of the species, here given,
j. 8, which shows the palps in situ, and there is so strong a

FIG. 8. /
P. acuminalus ; j
rather more than j
one-third natural
size. Lesmahago. |
Mus. Prac. Geol. \

Specimen show-
ing both first and
second pairs of
palpi, a, b, and the
swimming foot c.

divergence between the front filament a, and the lower one 6, as-
to render it probable they are not mere branches of the same palp.
6 is far more imperfect than a. c, is the swimming foot (ectognath)
in situ.

Swimming Feet, figs. 5 to 9. — The great basal joints of these organs
are squarer in outline and^their serrate edges placed more vertically
(i.e. more parallel to the general direction of the plate) than in P.
bilobus, or P. anglicus, Plates I., VII., in order apparently to accom-
modate their shape to the elongate form of the head, The terminal
joints, too, of the limb are less expanded and more linear than in the
above-mentioned species.

The size of the largest fragments would give about four inches-
and a half for the length by two inches and a half broad. The great
subquadrate basal joint occupies full two-thirds of the length ; it is
straight along the inner margin, rather square at the outer and
upper angle, rounded on the outer side, and has the notch for the
attachment of the remaining joints deep. On the lower third, behind
which the breadth lessens, the basal margin is convex. The entire
joint is thickened, and most so from the notch obliquely upwards ;
a ridge runs along the convexity, and another near the straight
inner edge. The terminal serrate portion is narrow-oblong, and set
very obliquely on the rhomboidal neck, from which it is obscurely
divided. Its upper (forward) margin is strongly arched, and the

€4 BRITISH FOSSILS.

straight serrate edge furnished with fourteen teeth, besides a pro-
minence on the very small hasal lobe. The uppermost tooth is
minute, the second largest of all, but not greatly larger than the
rest ; all are short-conical, tolerably equal in size, and a little curved
as well as set obliquely, pointing backwards.

The remaining joints, figs. 7, 8, 9, are well exhibited in three or
four specimens, of which fig. 7 shows the impression of the upper
side (see for comparison Plate VI. fig. 1.) Figs. 8, 9, are impressions
of the lower surface (see fig. 2 of the same plate).

Basignathite. — The second joint b is very narrow, almost linear,
and fully three times as wide as long ; the third (or ischygnathite) is
linear (?) on the under surface (fig. 8 i) but greatly produced forwards
on the upper (fig. 7), so as to touch, by its projecting boss, the fifth
joint. The general form is rudely trigonal, or rather trapezoidal,
the upper straight edge being only about half the breadth of the
lower, which is sigmoid, and near the boss tumid.

The fourth joint (merognathite) is spherical- triangular before and
behind, but on the lower side (fig. 8) it is produced into a long
straight process which fits the inner angle of the bend of the limb ;
a deep notch on the forward edge receives the condyle of the fifth
joint. The outer or front margin is very convex, almost gibbous,
and forms the prominent forward angle of the foot, which is more
strongly bent than in any other species.

The fifth joint (carpognathite) is narrow-linear on the upper side,
but much broader beneath, about seven lines long by ten or eleven
"broad, with a rounded boss anteriorly about midway along the joint,
and a deep sinus at the hinder edge to admit the great process from
the—

Sixth joint (prognathite). This is broad-linear, or oblong, (the
sides straight and parallel) not quite twice as long as broad, exclu-
sive of the lobes above and below. 'The upper lobe is rounded,
fitting into the posterior concavity on the margin of the preceding
joint, the lower lobes are unequal, the hindermost being largest and
most pointed, the forward one rounded and shorter, the notch deep,
rather wide and straight edged at the point of attachment of the
last joint (d).

(d.) (Dactylognathite.') This is two and a half times as wide as long,
contracted at the base, widest above its middle part, and ending in
a blunt point. The margin of this and the preceding joint are
minutely serrate.

Locality. — Lesmahago, an abundant species. Collected by Mr. K.
Slimon. The specimens are all in the Museum of Practical Geology.

BRITISH FOSSILS.

PLATE I. FIG. 17.

EUBYPTERUS LANCEOLATUS.

GEN. CHAR.* ETJRYPTERUS, Dekay, 1826. Body as in Pterygotus, with
12 segments, eyes subcentral, antennae without chelae.

E. elongatus, postice attenuates, articulis 12, quorum 10 transversis,
pemdtimo oblongo ; caudd acuta producta, ad basin tumida.

SYNONYM. Himantopterus lanceolatus, SALTER, in Quart. Journ. Geol.
fe'oc., 1. c., p. 28, fig. 5 (tail joint).

Perfect, except the carapace, which, when the plate was engraved,
was supposed to have resembled that of P. acuminatus. It is,
however, almost certainly an Eurypterus, from the elongate-linear
caudal joint, but the shape of the swimming feet is more linear
than usual in the genus. It is here figured because of its associa-
tion with the Pterygoti in my former notice.

Body two and a half inches long, by three-quarters wide in the
broadest part, which is about the fourth segment ; from thence it
tapers very gradually to the last. The anterior segment is narrow
(short), not above one-fifth as long as wide, with its ends recurved ;
the next, not much broader, is straight posteriorly. The last thoracic
ring (sixth) is three and a half times as wide as long, with the
posterior angles a little produced ; from thence the joints are larger
and less transverse, the tenth being onty half as wide again as long.
The penultimate joint is about as long as wide, but narrowed
posteriorly.

The terminal joint (telson) is three-quarters of an inch long and
only two-tenths wide ; it is regularly conical and acute, has a
median keel (apparently tumid at the extreme base) nearly all the
way down, and also one along each edge.

* For remarks on the generic character of Eurypterus, see pp. 35. 38. It differs
from Pterygotus chiefly in the subcentral eyes, but also by the want of the large chelai
to the antennae.

It is hoped to illustrate this genus in a future monograph, meanwhile the reader is
referred to the Quart. Journ. Geol. Soc., vol. xv., for information on the species.
[1. E

66 BRITISH FOSSILS.

The sculpture is rather obscure, strong on the anterior half of
each segment, and faint over the rest ; the borders are smooth.

Swimming Feet. — These are the only appendages found with the
present species ; they resemble those of Pterygotus bilobus, and,
when laid back, reach the end of the fifth segment. The third
joint is very obscure ; the fourth trigonal with the longer side
outwards, and but little convex ; the fifth irregular, its produced
outer edge overhanging the oblong penultimate joint.

This latter (cT) is about twice and a half as long as wide, rather
broadest at the bilobed end, the notch deep ; lobes rather acute,
the inner much exceeding the outer in size. Terminal palette ovate,
its length (measuring from the notch) equal to the penultimate
joint without the lobes. Margins minutely crenate.

Locality. — Lesmahago ; only one specimen known. (Museum of
Practical Geology.)

BRITISH FOSSILS.

PLATES III. TO VII.

PTERYGOTUS ANGLICUS.

SPEC. CHAR. P. gigas, 6-8 ? — pedalis, capite transverse, antice angus-
tiori truncato, segmentis corporis transversis, penultimo percarinato (subtus
carina brevi subcentrali), vix expanse, cauda ovata breviapiculata, carina
mediana paullo elevata.

SYNONYMS. P. anglicus, AGASSIZ (1844), Poissons Foss. Vieux Gres
Rouge, pi. 1 ; M'CoY in LYELL (1855), Elem. Manual, 5th ed. pp. 419,
420 (restored). SALTER in MTJRCHISON'S Siluria, new edition (1859),
foss. 21, fig. 1, restored ; Trans. Brit. Assoc., 1856, Rep. Sections, p. 75.
Palteocarcinus alatus (AGASSIZ olim) fide PAGE, in Trans. Brit. Assoc.,
1855, vol. xxiv. Rep. Sections, p. 90.

The liberality of Lord Kinnaird and of the officers of the Watt
Institution, Dundee, has placed at our disposal a magnificent series
of this well-known species, including most of the fragments from
which Agassiz drew up his original description. We have also
to thank Colonel James, Director of the Ordnance Survey, and
Mr. David Page, of Edinburgh, for their kind co-operation.

Until the carapace, Plate III. fig. 1, was obtained, no very com-
plete notion could be formed of the probable size of the fossil. It
was a less elongated species than P. acuminatus, but taking the
proportions of the head and the widest body rings as a guide, and
comparing these with such species as P. bilobus, the entire length
could not have been less than six, and from the size of the epistoma
and some other parts probably reached eight feet in length ! There-
are no living Crustacea which can match this in bulk.

And it was apparently of considerable thickness, almost cylindrical ;
the crust, however, appears to be very thin and paper like, and only
thickened where requisite for the attachment of strong muscles, as
in the swimming feet ; or along the ridges and margins, — the ser-
rated parts of the mouth, &c.

The carapace, now first described from a young specimen, mea-
sures six inches and a half long and fully nine inches wide at the
broad base, but narrows considerably towards the front, where it is
less than five inches and a half broad.

E2

68 BRITISH FOSSILS.

Our figure shows it compressed a little obliquely, but, allowing
for this, it is not far from the true shape, and it is probable that
not much of the margin is lost on the right-hand side, while enough
remains of the other to indicate that the outline was somewhat
curved. Two other specimens in Lord Kinnaird's cabinet show the
curved outline. The eyes are distinctly visible on each side, and are
as large as crown pieces.

The head must have been considerably more convex than at
present, since in our flattened specimen it is corrugated all over ; it
is sub-pyramidal in shape, truncate or but slightly arched in front
between the eyes, and concave posteriorly. The side margins (so far
as visible) and the front are strongly crenate, but not tubercular ;
the general surface appears smooth or minutely punctate, but not
anywhere marked by plicae. The eyes occupy the outer angles of
the head ; they are oval, an inch and a half in the largest diameter,
and about an inch broad. The lenses are rather large, about eight
rows in one-tenth of an inch, and in this pressed specimen are
rhomboidal rather than hexagonal, at least in arrangement ; this
may be due to pressure only.

The entire head, compared with that of P. acuminatus, is broad
and short, and much narrowed in front, so as to be intermediate in
shape between that square-headed species and the forms with
semioval carapaces. The eye is much larger in proportion.

Epistoma and Lalrum, Plate III. figs. 2-5 (6 ?). — This piece,
which is the epistoma or under side of the front of the head, occurs
in tolerable plenty, and is the portion formerly supposed to be the
carapace itself (see p. 6). From a very perfect and large specimen in
the British Museum, a reduced figure (fig. 5) is added, which justifies
the inference above drawn as to the great size of the animal. The
figured specimen, 2, is the same as that figured by Agassiz, and is
nearly three inches from back to front, but we have other specimens
which measure four inches and a half long, and were probably
-sixteen or eighteen inches wide.

The " seraphim," as the piece is called, is straight or only sinuous
in front, but broadly wedge-shaped behind ; its extremities are un-
known, unless fig. G be the lateral termination on one side. It
consists of a central arrow-shaped piece and two widely-expanded
wings or lateral lobes which project backwards nearly as far as the
shaft or central lobe, forming with it the broad salient angle of the
posterior margin. These lobes are not, however, united with the
shaft but overlap it with thickened edges on each side, giving it an
appearance of contraction in the middle ; it is, when detached, a

BRITISH FOSSILS. 69

linear piece, somewhat dilated at the base, convex along the median
line, deflexed at the sides, and expanding at the base into a
broad arrow-headed plate, the point acute, subtending a variable
angle (generally about sixty degrees), and reaching nearly to the
front. This portion is divided from the general surface by sutures,
but not quite separable. The apex of the central lobe is expanded,
rounded, and marked with radiating plaits. As in all other parts
of the crust the plicse which closely cover the surface are transverse
and but little curved in front, but become semicircular further back,
and then semi-ellipses, and even cones, closely tiling over one
another. It is this feather-like arrangement, combined with the
shape, which must have suggested the term " seraphim." The ex-
treme margin is smooth. The plicaB on the arrow-headed central
piece of the labrum follow the same order from before backwards,
and become elongate and prominent along the central ridge, forming
tesselloe rather than scales.

Body Joints, Plates IV. and V. — The segments of the thorax and
abdomen may easily be arranged in their right order, from com-
parison with those of the preceding more perfect species. Plate IV.

FIG. 9.

Pterygotv.8 ang-
licus, from the
second to the
ninth body ring;
one-fifth the na-
tural size.

Lowest beds of
Old Red Sand-
stone, Tealing,
Dundee. This
specimen is in
the Museum of
the Watt Insti-
tution, Dundee.

\.

70 BRITISH FOSSILS.

represents all the anterior segments we had observed when the
plates were engraved. But since their completion, a cast (agreeing
very nearly with the figures in Plate III.) of a line specimen of the
anterior body rings, and nearly a foot wide, has been sent up by
our correspondent, Mr. W. Miller of Dundee. It is from a new
quarry at Tealing, Forfarshire. The specimen is in the Museum
of the Watt Institution, Dundee, and a woodcut, one-fifth the
natural size, is given of it in p. 67. From the second to the ninth,
the segments are all united, and the anterior ones have slipped
a good deal over one another so as not to present quite their full
dimensions.

1st Segment. — This appears to be wanting both in the Tealing
specimen, and in the specimens figured in Plate IV. It was, pro-
bably, narrower than all the rest and had the outer posterior angle
much rounded off.

2nd Segment. (Woodcut, No. 9). — This is five times as wide as
long, somewhat arched in the middle, and much bent forward at the
sides, with indications of lateral processes a, a, similar to those in
the third segment. The lateral edges are very oblique : forming an
angle of about 70° with the posterior edge.

3rd Segment, Plate VI. fig. 1. — This is Agassiz's figured specimen
in his Table A, upper right-hand figure. It is four and a half times
as wide as long, our largest specimen above ten inches wide. The
posterior angles are rounded off, the anterior produced into lobes an
inch in length, a a. The lateral edges are less obliquely truncated
than in the second segment.

4th Segment. — Wanting in our plate ; it is the largest and broadest
of all in the Tealing specimen (woodcut 9) ; its sides are less oblique
than in the third segment.

5th Segment, Plate IV., fig. 2. — Fully five times as broad as long,
the sides are nearly rectangular, not oblique, the posterior angles
very little rounded, the anterior not (?) produced. Our largest speci-
men measures more than a foot wide and two inches and a half long.

6th Segment, Plate IV. fig. 3.— Of the same shape as the fifth,
but only four times as broad as long.

Of the remaining rings, figs. 5, 6 show imperfect fragments.
They gradually taper backwards, as indicated by the dotted margins,
and become thus narrower in proportion to their length, but exhibit
no other difference, as we learn from the above perfect specimens, as
far as the ninth.

Plate V. fig. 1, can scarcely be any but the tenth segment. It is
about once and a quarter as wide as long, the sides straight, and
the posterior angles a little produced.

BKITISH FOSSILS.

The llth segment, tigs. 3, 4, suddenly changes shape, it is half
oval, with both ends truncate, and its length is rather more than
three-fourths of the width. The base is contracted, the sides curve
boldly outwards, and again contract at the produced and hooked
posterior angles. The segment is thus much broadest behind. We
have both upper and under surfaces, the former is carinated all the
way down by a strong median ridge, wider and less prominent at
first, then sharply elevated and covered with coarse squamse. The
under side, fig. 3 6, has no median ridge except for its middle
third, and this, which begins by a gentle elevation, ends abruptly
rather more than two-thirds down. It is closely covered with large
squamae, and probably indicates the place of the anal opening. The
lateral and posterior margins are also bordered with tubercular
squamse, largest and most conspicuous on the sides. Our finest
specimen is three inches and three-quarters long, and four inches
and a quarter wide behind the middle, where the width is greatest ;
at its upper end it is only two inches and a quarter broad.

In the same beds, near Forfar, penultimate joints occur, which
are probably of the same species, but show a marked difference
from those in the plate. An upper and under side is here figured.

A the upper side,
and B the un-
der, showing
the anal ridge
a. Base of
Old Red Sand-
stone, Leys-
mill, Forfar-

72 BRITISH FOSSILS.

The former is destitute of any carina ; on the latter an abbreviated
(anal ?) ridge exists, but on the posterior third only (exactly as in
P. gigas, Plate VIII. figs. 6, 7). The proportions also of these joints
are different from that of the corresponding part in Plate V. figs. 3, 4,
being greatly more transverse ; two-thirds as long as wide in fig. 1 ,
and about three-fifths in fig. 2. This proportion is not very different
from that of P. gigas, though the shape is so different. May these
not be differences of sex, instead of indicating a second species?
The ridge (a), supposed to be anal, is present in all the species, either
subcentrally or on the hinder edge of the segment.

Telson, Plate V., figs. 5, 6. — The tail joint (12th) is a broad oval,
contracted at its base of insertion, widest posteriorly below the
middle, and shortly apiculate at the tip. It is but little carinate on
the dorsal view, fig. 5, and flat or with a very slight median ridge
below fig. 6. In a specimen six inches long the apiculus does not
project half an inch from the general margin, which is squamate and
serrate, but not strongly so. The apiculus itself is not serrated.

Sculpture.

The whole of the body rings are ornamented with a similar
sculpture, although not equal in size or distributed exactly in the
same way over all the segments. Curved plicae, like those which
occur on the epistoma, occupy the anterior half of each body
segment, and are from one to two lines wide, in open semicircular
curves upon the middle parts and anterior angles of the segments,
but on the front edges they are nearly straight lines and much more
crowded.

This arrangement is nearly uniform for the first five or six rings,
the plicae ceasing rather abruptly about the middle of the segment.
In the hinder ones they cover a larger surface, Plate V. fig. 1, and on
the under sides of all the segments (Plate IV. figs. 5, 6), they also
occupy nearly all the surface, though more sparingly placed on the
posterior half. On the llth segment, the plicse reach down along
the central keel, but are absent from the outer angles, and on
the under side, fig. 3 a, they occupy a still smaller area ; while on
the caudal joint only a small portion near the base or insertion of
the joint is marked by them.

In the hinder rings, the tenth and the two last especially, the
sculpture on the dorsal side is more angular; the plicse being
longer and narrower than even on the ventral side, where it is
usually more angular than on the upper surface. As inattention

BEITISH FOSSILS. "73

to this point might mislead in comparing with other species
(P. gigas, for instance, Plate VIII.), it is of consequence to note
this difference in the ornamentation of different portions.

Appendages.

Antennae, Plate VI. figs. 4, 6. — They were of great size. Plate VI.
fig. 5, shows the largest we have seen, but a somewhat smaller size
(fig. 4) is not at all unfrequent. There are four joints, including the
free terminal claws.

Of the first articulation only short fragments remain, it is nar-
rower than the second, which is linear, scarcely contracted at either
end, and in the largest specimen must have been four inches and
a half long and one inch and a quarter broad. The penultimate
joint, which is produced into the fixed claw of the chela, is rather
suddenly swelled, and increases in width outwards to the insertion
of the terminal joint. The produced portion is fully four inches
long, rather narrowed at its insertion (so as to be a little fusiform),
and thence tapering to the abruptly curved tip, which bends up at
a right angle, and is frequently half an inch long and pointed. The
opposed free claw is of the same shape, but more equal in breadth,
generally longer, fig. 2, than the other, but sometimes the two are
nearly equal (fig. 1). Occasionally the moveable joint is largest,
fig. 6, and overhangs the other considerably.

It is difficult to say which was anterior, but from the curvature
probably the free joint was forward, as in our figure. Each half of
the forceps similarly armed with about four primary and ten or
eleven secondary teeth, three or four between each pair of primaries.
These are set on at right angles, or rather pointing a little forward
on the fixed finger, but on the moveable claw decidedly backwards.
They appear to have been much compressed, and were so long that
when the chela was closed they shut side by side like the blades of
a pair of shears ; and they are placed opposite to one another as if
for the purpose of cutting as well as seizing. The middle pairs are
longest, sometimes measuring half an inch. The pair next outwards
from these are nearest in size, and the outermost and innermost
pair (when the latter are present) are smallest.

The shape of the large teeth and of many of the smaller is ovato-
lanceolate, constructed just above the immediate base, and then
expanded into a lancet form, and longitudinally striated, the strise
radiating a little from the base on the forward edge. Some of the
smaller teeth are simply conical, and the stria tion of all is about
equally coarse.

74 BRITISH FOSSILS.

Endognatks, Plate VII. figs. 4 to 7. — There are five or six specimens
in the Scotch collections more perfect than that figured by Agassiz
(middle left-hand figure), and of larger size, fully four inches and a half
long. The palpus, c d e, was probably five or six inches in length,
and of considerable thickness. Some fragments even indicate a still
larger size for the jaw.

The mandible is of an oblong form, the front and back margins
nearly parallel. The serrate termination of the lamina scarcely at
ail expanded into a lobe, and the posterior or basal portion (p)
which occupies nearly half the entire length is produced obliquely
backwards at a wide angle. This portion is straight in front and
only slightly sinuous along the hinder edge, which shows traces here
and there of striae perpendicular to the edge, probably due to the
insertion of muscular fibres.

The serrate edge is nearly straight and very oblique forming an
angle of about 120° with the front margin. There are about twelve
strong teeth, of which the upper six or seven are free, lanceolate,
curved, and dilated below, with a constriction as if articulated, and
the remainder are connected so as to form ridges upon a thin plate.
Minute intermediate ridges occur between these. The posterior
angle of the serrate edge is produced a little into a small lobe b,
covered with deep punctures as if for the insertion of stiff hairs or
setse. The upper edge is not at all expanded or overhanging as in
P. acuminatus, the teeth starting at once from the upper angle in
a line continuous with the front margin (this is not the case with
fig. 7, in which there is an overhanging lobe).

The general surface of the mandible is covered with obscure plicse,
which become distinct and large along the front margin, which is
thickened ; the rest of the lamina is rather flat, the base is thin and
almost membranous at the edge.

The palpus is long and stout, directed straight outwards, and
consisting of at least five, and probably more joints, of which the
basal one (c) is more than twice as wide as long. The next (cZ)
unceolate and thickened at the distal end, rather longer than wide.
The third takes an elongate form, but is still broad, and its end
thickened and somewhat bilobed (e). The next (/) is still longer
in proportion, swelled, and a little crenulate or spiny at the tip
(compare with Plate IX. fig. 7.) We have no more joints, but
in Agassiz's figure the succeeding joint, the fifth, is clearly shown.

The surfaces of all these joints are covered with transverse plicae.

Maxilla ? fig. 7. — It is probable that fig. 7 indicates a second pair
of endognaths, since the proportions of the plate are so different,
fig. 7 being considerably longer before the insertion -of the palpu

BRITISH FOSSILS. 75

thafi fig. 4, and having an overhanging rounded lobe in front above
the insertion of the teeth. Some specimens agreeing with this in
proportion have the basal lobe of the palpi broader.

Swimming Feet (Ectognaths), Plate VI. figs. 1 to 3, Plate VII.
figs. 1 to 3. — The large basal joints of these organs are among the
most characteristic parts of Pterygotus, and were at first supposed
to be the mandibles or maxillae, as they are most frequently found
detached from the other joints of the limb. Agassiz figured a
portion as a part of the tail flap, and we reproduce his original
specimen, Plate VII. fig. 3. It will be best to describe this portion
first. It is the —

Basal Joint (Coxognathite), Plate VII. figs. 1 to 3. — These are six
inches and a half and even seven inches long ! and not less than three
inches broad, gently curved (flask-shaped) convex, with the outer
or forward edge thickened, and concave on the inner or hinder side,
with the large basal portion almost orbicular, but narrowing into
the neck, and the terminal lobe again somewhat broadened and sub-
rhomboidal, with the serrate border placed obliquely to the general
direction of the entire joint.

The teeth are twelve in number, gradually longer from behind
forwards, the first often five lines long, and three broad at base.
They are conical, a little curved and grooved down the middle, but
not at all articulated to the base. Being set on a straight margin
and regularly increasing in size forwards, they present a serrate
edge along the points, rounded oft" a little behind into a very small
basal lobe 6. There are the same number of teeth in young as in
mature specimens.

Large tubercular plicae cover the whole surface, except the inner
thin margin of the terminal lobe, and these are concave everywhere
to the border, except towards the inferior angle behind the attach-
ment of the foot (Plate VII. fig. 2 c), where they present their
convex side to the margin ; and hence this portion is easy to
identify, even in fragments.

The limb beyond the large basal joint is very suddenly contracted.
The point of attachment for these is very conspicuous, as a deep
notch in the foliaceous base, about half way up on the outer side,
and from this point to the upper angle of the serrate tip is the line
of greatest convexity. The basal edge is rounded below, but angular
where it joins the inner margin.

The other joints of the limb are represented in Plate VI. figs. 1, 2 ;
and we are able to give a more complete account of them in this
than in any other species ; fig. 1 represents the upper and fig. 2 the
lower surface of the limb.

76 BRITISH FOSSILS.

b. The second joint (basignathite) is transverse, more than twice
as wide as long, and furnished anteriorly with a large rounded boss
occupying the exterior third of the joint (see fig. 2), broken off from
the limb and left attached to the coxal segment in fig. 1 at 6*. Its
hinder articulating border is somewhat concave, its inferior angle
rounded and produced.

i. The following joint is subtrigonal with rounded sides on the
upper surface, and with an obtuse angle projecting over the centre
of the following joint, but on the under surface it is rhomboidal,
more than twice as wide as long, and with the distal and proximal
edges nearly parallel (ischygnathite.)

m. The fourth joint is trigonal, the outer edges wide, convex,
and forming the angle of the limb, terminating in a rounded process
extending half way down the following joint. On the upper side,
fig. 1, the distal articulating edge is produced ; on the under side,
fig. 2, deeply emarginate to receive a process from the fifth joint
c a. The inner side of this joint (merognathite\ which is rather
a difficult one to describe, is much narrowed, and terminates in an
acute angle opposed to the wide basis of the outer margin.

c a. Of the next joint (carpognathite] it is equally difficult to give
a clear idea ; its shape is irregular. It is somewhat crescentic on the
upper surface, its outer side much the longer, and its distal margin
oblique, nearly straight for the greater part of its length, but the
outer angle truncated, and the inner notched. On the under side it
follows the shape of the preceding joint, and has a prominent
median process above to fit into the notch of it. Its distal margin,
too, on this surface is sinuous, and less oblique than on the upper side.

p. (and fig. 3.) The penultimate joint (prognathite) is flattened (to
form with the last, d, a swimming palette.) Our largest specimen
measures two and a half inches in length, by one and a half at its
broadest part. It is somewhat quadrangular, but one-third broader
below than above. Its outer edge is perfectly straight, longer than
the inner, and terminating above as a narrow rounded lobe, behind
which is a deep emargination, continuous with the curved outline of
the inner margin. The latter is produced inferiorly into a subtri-
angular lobe (3 c), broader than the superior process of the outer
margin above described. The rest of the inferior border (d) is
nearly straight, and forms almost a right angle with the straight
outer margin.

d. The terminal palette (dactylognaihite) is broadly ovate, twice as
long as broad, its apex rounded, its outer margin quite regular ; the
inner a little flattened above, leaving room for the play of the
palette against the penultimate joint, as in the swimming crabs.

BRITISH FOSSILS. 77

The surface of the great basal joint is nearly covered with large
plicse or squamse, the convexity of which is outwards over the
lower and hinder half, and inwards along the front margin. The
other joints are more strongly ornamented, the plicse coarsest on the
exterior margin; on the three or four terminal joints they are only
obscurely visible except on the margin.

The margins of at least the two last segments are beautifully
crenulated all round, with appressed serratures ; these are largest
at the apex and inner edge of the terminal swimming palette.

Metastoma, Plate VI. fig. 7. — The only piece which remains to
be described is this large oval plate, deeply notched at the broader
anterior extremity, regularly rounded on the sides, and very slightly
truncate at the posterior end. These plates are sometimes four
inches long and three broad, and are oval, the greatest width being
less than half way from the notched end; flat on one side and
of but slight convexity on the other, except at a point on the median
line about one-third distant from the smaller end, where there is a
prominence (probably the point of insertion). They are more
covered with sculpture than in the species previously described.

FIG. 11.

Packets of eggs or ovisacs (Parka decipiens). No. 1 is from a specimen in the
cabinet of Lord Kinnaird.

(Parka decipiens, Fleming. See Siluria, 2nd ed. chap. 10.) These
occur too often with Pterygotus not to be suspected as part of its

78 BRITISH FOSSILS.

structure, and are found with the P. anglicus in Forfarshire and
Perthshire ; also, with P. ludensis at Kidderminster, and P. proUe-
maticus at Ludlow.

Four fine specimens lent us by Dr. Balfour, of the Botanic Gar-
dens, Edinburgh, show clearly that the bodies in question cannot be
referred to seed vessels or receptacles, or indeed any other portions
of a plant. There is no trace of a style on any of the carpels of the
supposed fruit, nor of a leafy involucrum below it.

They are rounded masses, one to two inches broad, and composed
of numerous oval or hexagonal areee, a line or two in diameter,
which are now flat, but appear as if they had been compressed from
a nearly globular shape, not crowded over each other, but arranged
in nearly one plane so as to form a disk.

A long pedicle, fully a line broad, is attached near the centre of
the disk so formed, or sometimes nearer its margin ; and from the
point of attachment the surface of the general enclosing membrane
is radiated or plaited to the margin, but only on one side of the
disk. The plaits are depressed lines, dichotomising and inosculating
a little, but seem to have no reference whatever to the arrangement
of the ova, which they cross without being interfered with by them.

The appearances presented would be best explained by the sup-
position of the fossils having been membranous disks of only a
moderate thickness, and containing a single series of ova in the
thickness of the disk. They are not superimposed one on the other,
as they would have been had they been contained in a pyriform sac,
but set at equal short distances apart, as if kept in their places by
the membrane of the disk that enveloped them.

Localities. — LOWER OLD KED SANDSTONE, Balruddery, Perth-
shire ; and Leysmill near Arbroath, Reswallie, Tealing, Carmylie,
and other places in Forfarshire. The specimens are chiefly in the
collections of Lord Kinnaird, Mr. Powrie, and of the Watt Institu-
tion, Dundee. One or two are in the Museum of Pract. Geology.

BRITISH FOSSILS.

PLATE XIV. FIGS. 1 TO 13 ; PLATE IX. FIG. 18 ?;
PLATE XII. FIGS. 1 TO 5 (AND 6 ?).

P. LUDENSIS.

P. major, segmentis carports omnibus transversis, decimo bis quam longer
latiore, penultimo subquadrato vix expanso, supra carina percurrenti;
cauda ovali breviapiculata obtusicarinata : super/icie toto pi ids curvatis
simplicibus ornato.

Under this name I would now describe, witli but little doubt of
its specific distinction, the fragments of a fine species very abundant
indeed in the transition beds of Ludlow, shown as they are in the
railway cutting near that town. All the specimens are in the
cabinets of Mr. Lightbody and his son. The same species is found
at Trimpley near Kidderminster, and we are indebted to Mr. G. E
Roberts for the means of illustrating some points not clear in the
specimens at Ludlow.

The materials consist of several body rings of large size, Plate
XIV. fig. 2, 3, 4, 11 ; a fragment of the caudal joint, fig. 12; the
epistoma ; a specimen, fig. 1, showing nearly all the body joints and
telson in position, but a good deal obliterated ; the serrate bases of
the swimming feet, figs. 8, 9 ; mandibles with palpi, figs. 5, 6, 7 ;
antennae, fig. 10 ; and to these must be added certain figures in
Plate XII., showing the antennae, figs. 1, 2 ; the post-oral plate,
fig. 3 ; the bilobed (abdominal ?) appendages, figs. 4, 5 ; and possibly
the portion of the swimming foot, fig. 6 ; together with the imper-
fect caudal joint in Plate IX. fig. 18. The two last may, however
belong to P. gigas, a species very nearly allied, and to which for
some time I believed the whole of the specimens referable. Again,
there is so much resemblance in certain points to the Scotch species,
P. anglicus, that it requires nice discrimination to separate the three
forms. The characters of the antennae, and also of the caudal
joint, will, I think, be sufficient. And if subsequent observation

80 BRITISH FOSSILS.

should tend to show that this " Tilestone " species is the opposite
sex of the P. gigas, it will still have been worth while provisionally
to separate them.

Body Joints. — The complete specimen, Plate XIV. fig. 1, shows
that the body was not greatly elongated, the segments being all
rather widely transverse, the seventh, for instance, being fully four
and a half times as wide as long ; the eighth and ninth are gradually
narrower, but the tenth still shows a width two and a half times
greater than the length, while in P. anglicus the corresponding
joint appears so have been no more than one and a half times the
length (see Plate V. fig. 1).

The penultimate joint is squareish, or rather inversely conical, not
much expanded below. It is about one-fourth wider than long (as
in P. anglicus), and this at the hinder part only. A strong central
keel runs down its whole length, covered with large squamse, and
the margins are similarly ornamented.

If the caudal joint, Plate IX. fig. 18, be of this species, it has lost
the terminal apiculus. It is nearly elliptical, the base truncated-
It is fully four inches long.

The sculpture of the body rings consists of open semicircular
squamse, flattened along the anterior border and more convex
behind, occupying the anterior half of the segment in the front
rings, and more in the hinder ones, till, in the eighth and ninth,
they nearly cover the segment. On the sides they are more elon-
gate, and, as in other species (P. gigas, for instance, Plate VIII.
fig. 5), those on the upper side are more elongate and pointed than
those on the lower. All the plicae are prominent and sharp-edged.
There are very few intermediate ones, Plate XIV. figs. 2, 11, but the
surface of the cuticle is generally roughened between the plicae.
Some segments show the plicae very large, fig. 2, and must have
been at least fourteen inches broad. Other specimens in the Ludlow
Museum show four or five rings overlapping, and some are sub-
cylindrical, and with sharp edges. The caudal joint (twelfth) is
broad-oval and shortly apiculate, less abruptly so than in P. angli-
cus, which, too, has a less regularly oval form, the greatest breadth
being below the middle. It is marked all the way down dorsally
by a strong carina covered with broad squamse, and the edges are
also squamate, in two or three rows. In the specimen from Trimp-
ley, fig. 12, the sides are marked by oblique radiating interrupted
lines.

Epistoma and Labrum (not figured). — This plate is as large as
that of P. anglicus, Plate III., and nearly like in all its parts to it.

BRITISH FOSSILS. 81

' Antennas, Plate XII. figs. 1,2; Plate XIV. fig. 10.— These re-
semble in general form those of P. anglicus, but have a more slender
shaft, tapering more quickly, and narrower and more conical teeth.
The teeth are intermediate in form between the species above men-
tioned and P. problematicus, the central one being long-lanceolate,
and the secondaries narrow, conical, and with coarse striae The
base of the fixed claw, Plate XIV. fig. 10, is furnished with a set of
stiff spines, as in P. problematicus, but the whole chela is propor-
tionably much shorter.

Endognaths, Plate XIV. figs. 5, 6, 7. —Of these there seem to be
two pairs, as in P. anglicus, and of very similar shape. The one
pair (fig. 5) resembles in all respects Plate VII. fig. 5, except that it
has the teeth more bent down. The joints of the palpus, like those
of P. gigas, have a squamose ridge along each side, and the ends of the
joints are bilobed. The second joint is three and a quarter times as
long as broad. This is nearly the proportion in P. anglicus, where
it is three times the breadth.

The other pair of jaws (fig. 7) have their anterior margin more
curved, and the teeth set on a more convex edge than in P. anglicus.
The first tooth a is set more backward, thick, and curved at its base,
and all are more curved than in the Scotch species.

The Post-oral Plate (Plate XII. fig. 3) may belong either to this
or to P. gigas.

Base of Swimming Foot, Plate XIV. figs. 8, 9. — These portions
are verv characteristic in all the species. In this the shape most
nearly resembles that of P. gigas, Plate IX. fig. 8, and the teeth are
short and blunt, as in that species, but the neck is shorter. From
P. anglicus, the shorter form, the short neck, blunt teeth, and con-
vex upper lobe (a) overhanging the teeth, distinguish it ; but the
sculpture raised into thick, prominent, boss-like plicse is almost
identical. The lower edge is tuberculate, and even spinous ; our
figure does not show this part. A little comparison of this specimen
with Plate VII. fig. 2, will show that both in the upper or front
edge (ft), and on the lower or hinder edge (6), the terminal lobe is
more prominent in P. ludensis. We do not know the other joints,
unless Plate XII. fig. 6, be the penultimate one. It has exactly
the form of that of P. gigas.

Thoracic? Appendages! Plate XII. figs. 4, 5. — The nature of these
is not understood, nor do these specimens show the characteristic
irregular base. But they differ specifically both from the similar
appendages in P. problematicus, Plate XII. fig. 16, and from the
more perfect one figured in Plate XIII. fig. 16, by their deep ter-

[1.] F

82 BRITISH FOSSILS.

minal notch. The outer edges are thickened, and the substance of
the whole appendage is thick. The lateral plicae run down in
oblique rows on the inner (?) surface, becoming more and more linear,
till they become straight lines like the pennse of a feather ; and on
the outer side, impressed distant converging striae cut up, as it were,
the whole surface into narrow bands, the terminations of these bands
being serrated projections in P. problematicus, but in this species
they come to an even edge on the notched border.

Ovisacs (?), Plate XIV. figs. 13, 13*.— The egg-packets (Parka),
found in plenty with this species at Trimpley, show the membranous
veil in several cases. The ova are of considerable size, generally
oval, and placed a little apart in the younger packets, fig 13, but
they become hexagonal or polygonal, from mutual pressure, in the
older ones, figs. 13*.

Localities. — Base of the OLD RED SANDSTONE, at Ludlow
Railway Station (abundant) ; at Trimpley, north of Bewdley, as-
sociated with Ptemspis Banksii. (Mr. G. E. Roberts' Cabinet.)

BRITISH FOSSILS.

PLATES VIII AND IX.

PTEEYGOTUS GIGAS.

SPEC. CHAR. P. maximus, 6-7 pedalis (?), capite haud truncate, semiovato ;
oculis anticis rotundis ; segmentis corporis ut in P. anglico, — penultimo
expanse emarginato, insuper piano, subtus carina mediana postica : cauda
rnagna ovali, crista elevata centrali (apice emarginato ?).

SYNONYM. P. problematicus, BANKS, Quart. Journ. Geol. Soc., vol.
xii. pp. 93, &c.

For some years a large Pterygotus has been known in the beds of
Downton Sandstone (Uppermost Ludlow Rock), worked for building
purposes at Kington, Herefordshire, and a description of many of its
parts was given by Mr. R. Banks, of Ridgbourne, in the Quarterly
Journal of the Geological Society for 1856. Since his description
was written, he has continued to labour assiduously to collect the
fragments, and has been fortunate enough to discover nearly all the
parts of this fine species. He has generously placed these fragile
specimens in our hands, and presented a series of excellent drawings,
which were formerly exhibited at the Geological Society.* In the
paper quoted above, the fragments were all considered to belong
to the P. problematicus of Agassiz, a species for which there is un-
fortunately very scanty material, but which, as originally described
(see below, Plate XII.) is a Ludlow Rock species identical with one
of the Kington fossils, but not apparently with the principal and
largest of them, here described, and which in many respects is very
like P. anglicus.

P. gigas has, in common with the latter species, the open scale-
like sculpture on the body rings, and the thick tubercular scales on
their margin ; the shape of the epistome and head is very similar,
but the latter is rounded and not truncate in front. The penulti-
mate body ring is wider and has a short keel on the upper surface
only (while P. anglicus has one on both sides above and below), ana

* See Quart. Journ. as above, note to p. 97. It ought to have been named after him,
had not a much smaller Kington species been already distinguished by his name.

F 2

84 BRITISH FOSSILS.

the tail joint or telson appears to be emarginate instead of pointed.
But if this character should be deceptive, there can be no doubt of
the specific difference, since this joint is furnished with a most re-
markable elevated crest or ridge nearly half an inch high, which is
quite absent in the Scotch species.

As the fragments indicate a species of the largest size, the above
specific name will not be inappropriate. The size of the chelate
antennae exceeds that of any known species.

There are two species in the Kington beds, P. gigas and P. pro-
blcmaticus, and it was of course possible that some of the parts,
assigned to the former might belong to the latter species. The
subsequent discovery of nearly all the parts of P. problematicus
shows that in this instance the fragments have been rightly
collocated.

Head or Carapace, Plate VIII. fig. 1. — Nearly semioval, convex,
the width three inches and three quarters at the broad base, probably
greater than the length. The specimen being imperfect behind, the
true length is not known, but the portion preserved is three inches
and a quarter long. The eyes are very large, three quarters of an
inch long, oval and prominent beyond the margin. They are placed
very near the anterior end, and the space between them on the
margin is about an inch and three quarters, while between the
convex inner edges of the eyes it is about an inch and a half. The
anterior border is arched and very slightly angular in front, with a
crenulate edge. The sides are convex (their margin not visible).

In the centre of the carapace, and forming an equilateral triangle
with the eyes, is an elongate tubercle. The general surface appears
somewhat rugose.

Epistoma, fig. 2.— The proportions of this plate and its sculpture
are very like those of P. anglicus ; and the specimen figured indi-
cates this part to be quite as large as that in Plate III. fig. 7.
The plicae on the upper or front portion (a) are crowded, and
but slightly curved ; those further back are semicircular or even
semioval, while those near the apex of the side lobes are narrower
and pointed as in the cognate species. Similar but smaller plicae
occur down the centre lobe, which does not appear to have promi-
nent elongate scales, nor is it convex as it is in P. anglicus. Its
base c is broad and spear-shaped.

Body Rings. — The anterior body rings, fig. 3, bear the squamae
only on their front half, and these are less curved and less crowded
than in the corresponding segments of P. anglicus. The edge of
the plicae is thickened. Figs 4 and o must represent large segments

BRITISH FOSSILS. 85

from a portion of the body further back than fig. 3, for the squamjB
cover the whole lower surface of the segment (fig. 5), and the greater
part of the upper side (fig. 4). They are greatly more convex than
in the Scotch species, the posterior ones especially being parabolic
or even pointed in form, frequently three-tenths of an inch long and
broad. Fig. 5 shows the closely squamate lateral edges of the
segment, which are convex and rounded in the forward portion and
sharply keeled behind. The front margin in both of these segments
is contracted, for articulation with the previous joint, and has a
broad groove running along its whole length. The hinder angles
are a little produced.

Penultimate segment, figs. 6, 7, 8, 9, and Plate IX. fig. 15. — This
joint is much wider than long, in the proportion of four inches and a
half to two inches and a half ; some specimens must have been fully
five inches long, and therefore nine or ten broad. The segment is
widest and flattest at the hinder end, the margins are compressed
and keeled, except at the thickened and contracted base, and the
angles (fig. 9) pointed and produced. The upper surface (fig. 7) is
gently convex, but without any ridge, while the lower (?) fig. 6 has
a short thick keel extending half way up. It terminates on the
hinder margin of the segment, which is rather deeply notched at this
point. The surface is thickly covered with plicae, both above and
below, ' but they are much more prominent on the lower (keeled)
surface than on the other, where they are mere surface markings
and often obliterated. They cover the whole of the segment, but
are less thickly placed towards the hinder margin, at least on the
under side (fig. 6). The margin itself is tubercular.

The squamate keeled lateral borders are ornamented with several
(about four or five) rows of oblique thick plicae, more prominent and
larger on the lower side ; these are continued from about the ante-
rior fourth of the segment, where the keel commences, to the pointed
hinder angle. Similar, but still larger, plicaB cover the central keel,
Plate IX. fig. 15a, and numerous shallow folds run obliquely back-
wards from the sides to the keel.

Telson or Tail- Joint, Plate IX. figs. 16, 17.— The dimensions of
this joint give the best indication of the size to which the species
grew ; its length was full five inches and the width four and a
half. The largest specimens of this part in P. anglicus, Plate V.
fig. 5, are rather longer but narrower. The general shape was that
of a broad and pretty regular oval, but truncated at the base, and
emarginate at the apex.* The underside, fig. 156, is flat, except

* Plate IX. fig. 15, is the only specimen which shows the apex. Perhaps there nay
have been a short central apiculus, as in P. anylicus.

86 BRITISH FOSSILS.

at the origin of the joint, while it is somewhat convex ; the median
line is even concave. Oblique folds or lines, like those on the pen-
ultimate segment, occur on the forward half. The upper side is also
flattened, but furnished along its whole length with a great central
keel, rather thick at its origin, but becoming narrower and more
elevated (six-tenths of an inch high in the centre), and then de-
creasing towards the tip.

Sculpture as in the preceding segment. The blunt ridge of the
central keel is covered with small squamate plates, and the margins
have four or five rows of oblique elongate ones. The general surface
is bare of plicae, except near the base, where they are numerous
and prominent both on the upper and under sides.

Appendages.

Ghelate Antennae, Plate IX. figs. 1, 3. — Fragments only are
yet found ; the large base of the fixed claw, fig. 1, is about five inches
long to the first tooth (in the largest P. anglicus it is not more than
three inches and a quarter), and one inch ten lines broad (nearly of
equal breadth throughout). The articulating edge (a) is long and
oblique, the joint narrowing considerably into the serrate claw. Of
this portion (6) there is but little preserved, but it shows the chela
to have had broad (probably subovate) cutting teeth, as well as
numerous close set smaller ones. These last are short-conical near
the base of the fixed claw, and coarsely striated parallel to their sides,
the striae branching from above downwards. Further out (as shown
in the separate specimen, fig. 2, which may be the free claw) the
smaller teeth are lanceolate and narrow, and the striae parallel.
These striae are very closely set, much more so than in any other
species. These teeth appear to have been irregular in size, and much
crowded ; a third specimen (fig. 3) shows three kinds, — the small
lanceolate one a, larger subovate secondary ones 6, and one a great
striate tooth c* apparently the median one (see Plate VI. fig. 5),
which is coarsely ribbed, and is besides serrate on the inner edge.

The endognath has somewhat broader and shorter teeth than that
figured in Plate VII. ; and the second maxillary piece is more curved
anteriorly. Mr. Banks' cabinet contains both.

Of the palpi (Plate IX. fig. 5-7) only fragments are left. Fig. 5
shows four joints connected, but all compressed in a direction
perpendicular to their length. Their diameter is half an inch, and

* A similar tooth (?) has heen figured in P. problematic™. See Quart. Geol. Journal,
vol viii. pi. 21. fig. 26.

BRITISH FOSSILS. 87

their proportions may be compared with those shown in Plate VII.
fig. 4 The second joint d is rather longer, and the third e not
quite so long as in P. anglicus. The other figured fragments are
less distorted ; fig. 6 shows the fourth joint fully one inch and a
half long, with the tip expanded and bilobed. In fig. 7, one of the
lobes bears a fringe of spines. All the joints show elongate squamse
on their outer side.

Svjimming Foot, Plate IX. fig. 4-9. — The great basal joint,
fig. 8, with its serrated tip, closely resembles in form and sculpture
that figured in Plate VII., the chief difference being the greater
width of the foliaceous base, and the more backward position of the
notch at the point of attachment for the succeeding joints. The
serrate terminal lobe, figs. 4 and 9, has broad stout teeth, as usual,
thirteen in number, slightly curved, the uppermost broader and
shorter than the rest, the lowest b a rounded lobe as broad as the
two preceding teeth taken together. The teeth are shorter than in
P. anglicus, especially the upper ones, so that the outline of the
serrate edge is more curved. The perfect specimen is only three inches
and a half long by two and three-quarters broad, but fragments
indicate a size equal to the largest specimens of the Scotch
species.

Of the other joints of the swimming foot only two or three
•specimens (fig. 10-12) have occurred. Fig. 30 shows the upper
surface of the right-hand swimming foot, with two complete joints :
the fourth (m) and fifth (GO), with a portion of the great penulti-
mate joint p*. The latter joint is better shown in another frag-
ment, fig. 10, which is in close juxtaposition, and has a fragment
of the fifth joint ca attached to it.

The fourth and fifth joints closely resemble those of P. anglicus
(see Plate VI.), but the form of the penultimate or propodite is as
usual characteristic. It is oblong, two inches and a half in length by
one and a half broad, and is but little broader at one end than the
other. The upper or proximal end is deeply bilobed, as in P. punc-
tatus, the lobes being apparently equally prominent, and the distal
or outer end is trilobed ; this is partly seen in fig. 10, but much
better in fig. 1 1, where the outer lobe a is pointed and prominent,
the middle one rounded and shallow, and the inner c truncate :
the last forms nearly a straight line ending in a sharp angle against
the straight inner margin.

Both outer and inner margins of the penultimate joint are serrate
with elongate appressed squamse, and the surface of the preceding
joints (the fourth especially) has close and rather elongate plicse.

88 BRITISH FOSSILS.

Of the terminal palette we have no trace ; its probable shape is
given in the dotted outline.

Only the metastoma, fig. 13, remains to be described. It is
greatly like that of P. anglicus, Plate VI., and chiefly differs in the
more contracted base, and large open plicae of the surface. The
notch is somewhat deeper. It may have been smooth over the
hinder portion, as in Plate XII. fig. 3, which is the same or a closely
allied species, and may be noticed here, though possibly it belongs to
P. ludensis, above described.

Plate XII. fig. 3. — This post-oral plate, in its anterior portion, a
good deal resembles that figured in Plate IX., the notch being a little
less deep only. The shape is much more elongate than in P. anglicus,
the length being as seven to four ; the width is greatest at the anterior
third, and the general shape ovate. The plicae are large and open,
and are confined to the anterior portion about the notch.

The basal joint of the swimming foot (fig. 6), found at the same
locality, is in almost every resp.ect like that of P. gigas, having
the teeth broad and short.

Locality. — Downton Sandstone (UPPERMOST LUDLOW Rock) of
Kington, Herefordshire. (Cabinet of Mr. R. Banks, of that place.)
Some specimens, presented by that gentleman, are in the Museum
of Practical Geology. Plate XII. figs. 3, 6 are also specimens in the
Museum, collected by Mr. A. Marston, of Ludlow. They were found
at the Ludlow Railway Bridge, in the passage beds at the base of
the Old Red Sandstone.

BRITISH FOSSILS.

PLATE XII. FIGS. 7-16, 20, 21 ; AND PLATE XIV.
FIGS. 16-18.

P. PEOBLEMATICUS.

P. magnus, segmentis corporis ornatissimis, — plicis minutis creberrimis
inter majores mixtis (segmento ultimo transverse, nee expanso, subtus
carina brevi mediana ?) : antennis dentibus longis, rectis, remotis.

SYNONYM. P. problematicus, AGASS., in Sil. Syst. (1839), p. 606, pi. 4.
figs. 4, 5 (? Sphagodus pristodontus, AG., tooth only, ib. fig. 6). STRICKLAND
and SALTER, Quart. Journ. Geol. Soc., vol. viii. pi. 21. figs. 1, 2 ; Siluria,
2nd ed. pi. 19. figs. 4-6.

As this is the principal, if not the only species in the true Upper
Ludlow Rock which has the usual semicircular ornamental plicae, it
is to this that the name problematicus should be given, and, fortu-
nately, on one of the minute original fragments figured in the
" Silurian System," the small intermediate plicae are to be seen
marking the species more definitely.

The large chela, figured as above under this name, by the late
Mr. Strickland and myself, proves to be really an appendage of
this same species, at least it is always associated with it in the same
bed. Again, the antennary portions, fragments of body rings, bases
of the swimming feet, post-oral plate, &c., figured on Plate XII.,
are all found in the Whitcliffe, Ludlow, or other localities of the
Upper Ludlow Rock, and clearly differ from the corresponding parts
in P. punctatus, the only other large species occurring with them,
as well as from those just described, which are characteristic of the
beds of passage above the top of the Ludlow series. P. problematicus
may now, therefore, be considered an established species, and the
cabinets of our Ludlow friends, Messrs. Cocking and Marston, have
furnished many of the materials. It occurs, too, in plenty, as Mr.
Lightbody's researches show, in the transition beds beneath the Old
Red Sandstone, Plate XIV. ; and Mr. J. Harley, to whom we are

90 BRITISH FOSSILS.

indebted for much valuable help, has been fortunate enough to
detect its fragments far up in the cornstones of the Old Red itself,
a higher limit than the genus had been known before to attain.

[If the large fragments from the transition beds above quoted,
and figured on Plate XIV., be of the same species, as the sculpture
indicates, the body segments attained a very large size, nearly three
inches from back to front. As it is possible these may belong to a
different species, I will describe these portions first.

Carapace (T), Plate XIV. fig. 16.— A fragment, three inches by
two and a half, has the surface sculptured, unlike the body rings,
i.e., much more finely marked, and without the regular increase in
size and curve of the plicae backwards. The anterior ones are
nearly as much bent as the hinder ones though smaller — all are but
slightly prominent, and are covered by numerous smaller plicse.

Body Rings, Plate XIV. fig. 17. — One of the broad abdominal
rings, two inches and three quarters from back to front : the articu-
lating front margin is rather deeply concave, and its edge is
obscurely striate longitudinally (like fig. 3). The plicse are very
numerous and close-set, not so large as in P. anglicus, or so straight
on the forward edge, where, however, they are very closely packed.
They are more open posteriorly, and cover more than half the seg-
ment, interspersed with very numerous minute semicircular plaits.

Another piece (fig. 14) is here considered as belonging to this
species, but it only shows the interspersed plicae over part of the
surface : and it quite possibly belongs to P. ludensis, or even to a
new species.

Penultimate Joint, Plate XIV. fig. '.18.— Of this we have only
the lower surface ; and as the plicae are restricted to the upper
portions, and only a few small ones are interspersed, it is possibly
not P. problematicus, but of the same species as fig. 15, mentioned
above. The width is greater than that of the same joint in P. an-
glicus or P. ludensis, being three inches and a half, while the
length is only two and a quarter, (or as fourteen to nine,) which is
about the proportion in P. gigas. The joint is not expanded
posteriorly as in that species, and the plicse are semicircular, not
pointed, on the lower side.]

In the true Ludlow rock but few body joints have been met
with, the two best are figured from Mr. J. Harley's collection, viz.,
Plate XII. fig. 20, must be one of the thoracic rings, and fig. 21,

BRITISH FOSSILS. 91

probably the tenth or last but two of the segments. Both show
the minute interspersed plica3 very clearly, and these small plicae
extend over nearly all the segment, while the larger ones are
confined to the anterior half.

Telson, as yet unknown, as also is the epistomian plate.

Antenna, Plate XII. figs. 7-1 0.— Fig. 10 is most probably part of
the stem, and shows the large and small plicae in perfection. Figs.
7 to 9, the large characteristic chelaB, which can scarcely be con-
founded with any other species, the teeth being so much elongated.
Fig. 7 is the fixed claw, with a widely expanded and largely dentate
base.* The shaft is parallel-sided (not tapering as in P. ludensis),
and the teeth long-lanceolate, the large one being much longer than
the diameter of the shaft, (in fig. 7, fully three-quarters of an inch
long,) the secondaries three or four on each side of it, with small
teeth interspersed, all linear-lanceolate, erect and remote, not
crowded at their bases. In the fixed ranms they are either erect
or (fig. 8) point forward a very little.

The striae on the teeth are very fine and close, f oblique some-
what on the great tooth, and more direct in the smaller ones. In
P. gigas and P. ludensis they are coarser, and the teeth broad.
The great terminal mucro is as broad and long as the primary
tooth, or even longer, and is bent at right angles to the shaft.

Swimming Feet, Basal Joint, Plate XII. figs. 11-14. — Several
fragments have been found of the great basal joint, and one
tolerably perfect from the Whitcliffe, Ludlow, fig. 11. It shows a
wide-expanded basal lobe, and the whole extent of the serrate tip,
with the usual number of teeth (thirteen, or rather twelve in this
specimen) ; and in fig. 14, the upper tooth being obsolete. Fig. 13 a,
from Ludlow, shows the full number.

The lobe in front of the teeth is arched and thickened in all the
specimens, (a character in which this species differs widely from
P. anglicus,} and the second tooth is more than twice the breadth
of any of the others, conical, and but little curved ; the remaining
teeth are long, straight, narrow, and separated by about their width
from each other in large specimens. These elongate teeth are very

* See P. ludensis (Plate XIV. fig. 10) for a similar chela.

•f See also Strickland's figure, quoted above. There is one lanceolate fragment (2 i)
in that figure, here reproduced, fig. 9*, -which is striated finely like the teeth. It
is serrated all down one side. Its nature is quite doubtful ; but it is associated with the
antenna ; and as the large primary tooth in P. gigas (Plate IX. fig. 3) is serrated posteriorly,
it is possible this may be the case in one of the chelae of the present species. There is
a small conical uncinate appendage in the same figure, Geol. Journ., that is yet un-
explained.— Quart. Journ. Geol. Soc., 1. c.

92

BRITISH FOSSILS.

distinctive of the species. I believe I am not mistaken in referring
Agassiz's figure of the Sphagodus tooth to this portion.

Metastoma (Plate XII. fig. 15, Plate XIV. fig. 19) is cor-
date-ovate, narrower at the bilobed end, and has its greatest
width below the middle (our figure does not express this well),
becoming angulated at that point. The notch is deep, the lobes
rounded (the base is broken off), surface marked with open squamae,
but only near the upper end and about the notch. This post- oral
plate is the broadest of any species known.

Fig. 1 6 is a plate of the same nature as those found with P. lu-
densis, and is possibly a thoracic or abdominal appendage, though,
as no species are known with any such attached, its nature is quite
doubtful. The small crenate fragment, fig. 17, probably belongs
to it ; a similar piece is attached at c to fig. 16. [The entire form is
better seen in P. arcuatus, Plate XIII. fig. 16, viz., a lobed broad
emarginate plate (d), in the wide notch of which is attached the
truncated sub-oval plate a, &.] A more perfect specimen is here
added in a woodcut, showing the thickness of the plate on the one
side of it. The obscure converging lines ending in serrations on the

FIG. 12.

Pterygotus problemati-
cus, Ag., thoracic or
abdominal append-
age ? nat. size.

Comus Wood, Ludlow,
in Upper Ludlow Hock
(Cabinet of Mr. J.
Harley, King's Coll.)

border are exhibited on one surface ; on the opposite, the oblique
close plicse running into parallel lines towards the margin, very
like the segments of a feather.

The base a a is much extended on each side, and in this respect
seems to be different from the figure above quoted, Plate XIII.,
which probably belongs to P. arcuatus.

Localities. — • UPPER LUDLOW ROCK, Whitcliffe, and many
places near Ludlow (Ludlow Museum and Museum of Pract. Geo-
logy 5 Cabinets of Messrs. Lightbody, Cocking, J. Harley, and
A. Marston.) Kendal, Westmoreland (Museum of Pract. Geology).

BKITISH FOSSILS.

93

Ludlow Bone Bed, Ludlow : Downton Sandstone of Bradnor Hill,
Kington. (Mr. R. Banks' Cabinet.) BASE OF OLD RED SANDSTONE,
Ludlow Railway Station (Museum of Pract. Geology). Cornstones
of Hopton Gate (Cabinet of Mr. J. Harley).

One of the most widely spread species ; it is probably this which
occurs in the Upper Llandovery Rock or " May Hill Sandstone" of
the Obelisk, Eastnor Park. A woodcut of it is subjoined.

EIG. 13.

Pterygotus problemati-
cus, Agass. ? frag-
ments of ectognaths.

Eastnor Park, Malvern
(Cabinet of Sir W.
Jardine.)

BRITISH FOSSILS.

PLATE XIII. FIGS. 8, 12, 13, 15, AND 16.

PTERYGOTUS AECDATUS.

SPEC. CHAR. P. major, segmentis arcuatis, plicis semicircularibus
parvis, nee squamulis minutioribus intermixtis.

The name is applied to a large and fine species, of which several
fragments occur in the Lower Ludlow Rock of Leintwardine, along
with the more common P. punctatus, Plates X., XI. It is clearly
distinct from that species, but except for the total absence of any
minute interspersed plicae, the body segments might be easily mis-
taken for those of P. problematicus, to which it is closely allied ;
and with it, in the same beds of Lower Ludlow Rock, occur
antennce (fig. 8), the obscure appendages (fig. 16), swimming feet,
maxillse, and other oral apparatus, differing specifically from those
of P. problematicus, and yet more distinctly separated from the
portions of P. punctatus, found in the same beds. Of these frag-
ments the body segment must receive the name, the other pieces
being only provisionally arranged with it. They all resemble the
corresponding parts in the Upper Ludlow species.

Body Segments. — Fig. 1 2 is clearly, from its shape, the second
body segment, seven inches broad and more than one inch and a
half deep. It is curved, and more oblique laterally than in P. anyli-
cus, the sides forming an angle of 65° with the base. The anterior
edge is much more sinuated than the posterior, owing to the deep
excavation to receive the first segment; but the central part is
strongly arched forward on both margins. The lateral anterior
process a is broken off, but enough remains to show it was pro-
minent. The sides are oblique, inclined forward at an angle of 80°
from the posterior angle, which is rounded off. The margin is
crenulated, the prominent minute sculpture confined to the anterior
third, but continued more faintly over a large part of the segment.
(The sculpture in the thoracic segments of P. punctatus, Plate X.

96 BRITISH FOSSILS.

though not carried over a much larger part of the surface, is far
more prominent and remote).

A specimen, crushed longitudinally (fig. 13), shows that the
species was rotund in section, as in P. punctatus and others.

Antennce.^ In all probability Plate XIII. fig. 8, represents the
antenna of this species. Its resemblance to those of P. problema-
ticus is very close. The shaft is linear, the long end turned abruptly
up, and the teeth straight, narrow, and remote, as in that species ;
but the chela is much more slender, three inches and a half to four
inches long, and the larger central tooth is scarcely longer than the
diameter of the shaft itself; while the secondary teeth, some of
them at least, approach it more nearly in size. The tooth at the
base of the large terminal mucro is appressed against it, and the
mucro itself (Plate XI. fig. 3) is sometimes oblique. All the teeth
are finely striate, the striae tending obliquely backward on the
principal teeth. There are numerous sharp, conical, minute teeth
between the secondaries.

Endognaths (Maxillce .?)— Most probably Plate XIII. fig. 15,
represents the first or second pair of these organs, and it is pretty
clearly referable to P. arcuatus, and not to P. punctatus, which
has much shorter and blunter mandibles. (Plate XI. fig. 6.)
It is elongate, or even falcate, the upper lobe a greatly convex, the
posterior portion (/) drawn out laterally instead of backwards ; the
surface closely sculptured all over. The teeth are not oblique,
straight, and conical as in P. punctatus, but lanceolate and curved,
and directed outwards. About ten or eleven are free, the rest con-
fused, either in a horny plate or mixed with setas. In this parti-
cular, and in the production of the lower lobe b, it resembles
P. punctatus, but the great curvature and elongation of the plate
distinguish it.

Base of Swimming Foot, Plate XL fig. 10. — Most probably, from
the very convex form of the anterior edge, and the greatly elongate
teeth, this belongs rather to the present than to P. punctatus.
[Plate XIII. fig. 14«, may, perhaps, represent this part in the latter
species.]

Post-oral Plate, Plate XV. fig. 5.— Found at Leintwardine, by
Mr. Alfred Marston. It differs from the corresponding plate in all
the species, having the lobes of the apex narrow, and nearly their
own width apart, the sinus between them being very wide and
shallow, instead of a simple deep notch. The plate is cordato-
lanceolate, for the upper two-thirds it is oval, the greatest width

BRITISH FOSSILS. 97

being rather below the upper third 5 the base is rather suddenly
contracted, and tongue -shaped.

Thoracic (?) Appendage, Plate XIII. fig. 16.— This has been
already alluded to (p. 92), as probably belonging to the species. It
is more perfect than any other specimen, though only the impression
of one side. The large ovate terminal plate a b, shows well the gra-
dation between the ordinary plicae and the long lateral plaits, the
middle line is bare of any ornament. At the apex are seen two or
three of those impressed lines, which are so much more conspicuous
on the opposite surface, and which seem to divide the plate into
laciniae, a. The plate is indented at its basal end, corresponding to
the central depression (ridge in the cast) of the preceding joint. This
joint is very irregular in shape, the lobes on one side, d, being single,
on the opposed side c double. Both are marked with minute plicae
near the edges.

Locality. — The above-mentioned fragments have all successively
come to light during the active researches of the Ludlow geologists
in the quarries of LOWER LUDLOW ROCK at Leintwardine, parti-
cularly in one at Church Hill. There are many new Crustacea to be
described from the same quarry, of one of which the head portion
has been accidentally introduced into this plate. Plate XIII.
fig. 17- See also p. 25, suprct.

BRITISH FOSSILS.

PLATES X., XI., AND PART OP XIII.

PTEEYGOTUS PUNCTATUS.

P. magnus, (5-6 pedalis?) capite (?), segmentis omnibus squamulis

remotis prominulis ornatis, — in articulis posticis per totum annulum sparsis ;
chelis antennarum elongatis ; palpis longi-fimbriatis. Pedibus natatoriis
articulo terminali elongate, penultimo expanso.

Of this very large and distinct species various fragments have
from time to time come to light, and have been communicated by
our friends Messrs. Lightbody, Cocking, and Marston, of Ludlow,
and especially from the cabinet of H. Pardoe, Esq.

They are from the quarry at Leintwardine, Shropshire, in the
Lower Ludlow Rock, where many fine starfish and other rarities
have been newly discovered. (Siluria, 2nd edition, p. 140.)

There is evidence of at least three, if not more, of the thoracic
rings. The hinder segments were decidedly longer in proportion to
their width than in the P. anglicus or P. gigas. We have also the
swimming paddles, which, without the great coxal joints, were
seven inches long, expanded in the penultimate joint and attenuated
at their tips ; of the mandibles, the palpi of which are strongly
fringed with long curved processes, and of antennae, witli slender
pincers at their terminations, and armed with numerous small
conical teeth. As all these parts present distinctive peculiarities
from other species, and as the tuberculatiou on the various speci-
mens found in this bed agrees in character, it is fair to combine
them as a single species, and figure them all upon one plate.

Of the carapace or eyes we have yet no trace. But the epistoma
(fig. 1) presents us with a singularly neat character for the species.
The upper portion of this organ is broadly sagittate or spear-shaped as
in other species, and offers a wider basal angle than that of P. angli-
cus, but the outer portion, which is quite straight and linear, (instead
of being clavate,) is bilobed at the tip ; and from the deep terminal
notch a raised central line is continued nearly all the way up the

100 BRITISH FOSSILS.

linear portion, and terminating in a slight prominence. The whole
piece is smooth.

Of the first body ring a fragment an inch and a half long and
one inch wide is figured (Plate X. fig. 2). It is the semi-circular
sweep of the outer edge of the segment, where it fits into the
scooped out portion of the succeeding (second) one. The rounded
margin a is serrated, the serrations pointing backward. The
sculpture is very minute, prominent, and confined to the forward
half, except a few marginal plica3 on the hinder edge. All are longer
than wide. Fig. 2a shows them magnified. Fig. 3 is without much
doubt the second thoracic segment. It is wider at the sides than in
the middle, and turns up abruptly at the forward angle to form the
characteristic process. Fig. 4 appears to be a larger specimen of
the third ring, it has the same characters of ornamentation. In
both the central portion is less arched than in P. anglicus or
P. arcuatus, and the sides less oblique and minutely crenulate.
A narrow (articular ?) furrow runs along the middle portion of the
anterior edge, followed by a convex ridge, which is bounded by a
row of prominent minute tubercles extending a good way out, and
nearly to the lateral margins. Behind this the anterior third of
the segment is occupied by the sculpture, which is much more pro-
minent and tubercular, and less scale-like than in the large Scotch
species.

The occurrence of this line of tubercles enables us to connect with
the species some very curious fragments, one of which is here
figured (fig. 8) with one or other of the body rings. When first
viewed the piece appears quite anomalous, the extended ends giving
the general form much the aspect of the epistoma, but a closer
examination shows that it has an upper surface b, and the impres-
sion of the lower side c, each with the sculpture pointing backwards,
and with no room for a median lobe. Of the epistoma we have
now obtained specimens (fig. 1, as above described), and it remains
therefore to explain this piece as one of the body rings, obliquely
pressed, (probably the exuviated crust only,) the angular edge being
indicated at a, and one surface (the inferior) c, being less disturbed
and altered in shape than the other, b. The dotted lines will give a
notion of what was probably the complete form. Fig. 9 is probably
a similar fragment. Figs. 10 and 11 have as yet no explanation.
Fig. 7 shows the true outline of another ring, which has been com-
pressed vertically in the rock, instead of laterally. These specimens
of course give the true idea of the convexity, which was very great.
The form was almost cylindrical.

BRITISH FOSSILS. 101

Of the intermediate rings we have very few fragments, but several
hinder rings, which must have been near to the extremity both from
their form and their being quite covered with the elongate tuber-
cular plicae.

Plate IX. fig. 7, from the cabinet of Mr. Marston, represents
probably the penultimate ring. It is two inches and a quarter long
by two inches at its truncated extremity, which is rather wider than
its base. The shape is thus nearly square, the sides are but very
slightly (perhaps not at all) curved, nor is the base a contracted or
the distal end 6 expanded or produced, as in P. anglicus. The edge
is crenate. Plate XIII. fig. 5 is from the Upper Ludlow Rock.

The caudal joint (telson) is yet wanting and should be sought
for, as in all probability it was not unlike that figured on Plate VIII.
fig. 1 1 has possibly something to do with it.

Mr. J. Harley, of King's College, has found a small specimen,
doubtless of this species (Woodcut, fig. 14), since the plate was
finished. It has the second to the sixth rings united, and the
pyramidal form of the front ring is very marked.

Fm- 14' From Lower Ludlow

Anterior body rings of U~ >— Rock, Leintwardine.

Pterygotus punctatus. I In the collection of

The first segment (____ ^=z== =====--_ J Mr. J. Harley.

lost.

Appendages.

Antenna;.— Of these great pincer-like organs only two chelae have
been found, one three inches and a half long, but these are quite
different in proportion from that of P. anglicus. The shaft is much
longer and slenderer, being quite eight times as long as wide, and
not much thicker at the origin than near the tip. The teeth are
much shorter, the central one is as long as the diameter of the chela
itself, and placed beyond the middle ; two other primaries nearly
equal in size and a secondary tooth are outside it, while only minute
teeth with a single primary near the hinge occur on the proximal
half. As many as twenty of these small conical teeth may be
counted in the inner half, and eleven or twelve on the outer. The
primaries are broad-conical (not ovate), striated and directed back-

102 BRITISH FOSSILS.

wards, and are not crowded at their bases by the smaller teeth
which vary much in size, but are all of them more or less conical
in shape like the larger ones. The terminal mucro is lost in both
the specimens ; a few tubercles occur on the shaft near the end,
fig. 2 a.

Endognaths and Palpi, figs. 5-8, and Plate XIII. figs. 9-11. —
There are several specimens and they present some strong characters
for the species. Plate XIII. fig. 9, and Plate XI. figs. 7 and 8,
show portions of the palpi, and fig. 5 an endognath with its entire
palp attached, and in the proper position in respect of the great
swimming foot c. From this specimen it would appear that the
remarkable spines of the palpus were directed forward. Figs. 8, 9,
show the great size these appendages obtained.

The teeth of the maxillary piece (fig. 6 a a*) are small, short,
and obliquely conical, not curved, and as in some other species
striate ; there are about seven distinct, and six smaller ones, which
last are either connected by a horny plate (as in P. anglicus,
Plate VII. fig. 5 6), or are confused with setse ; the state of pre-
servation does not permit us to decide which. The margin near
the teeth is punctate, indicating the presence of hairs or setse. In
some specimens the teeth are narrower and sharper.

[Fig. 10, though found in the same bed, must evidently belong to
a distinct species, and has been already referred to P. arcuatus.
Fig. 11 is probably a second pair of jaws (endognaths), as already
indicated in other species.]

Palpi. — The great palpi (of which fig. 6 only shows the base at
b, and fig. 5 a nearly perfect one in situ) are broader at their base
than the length of the serrate border a. They consist of only five
joints, all except the basal one bearing (a pair ? of ) curved processes,
while the terminal one, g in fig. 8, might even be considered as
an additional joint.* The specimen (Plate XIII. fig. 9), obtained
since Plate XI. was completed, shows all the joints complete,
and these resemble Plate XL fig 7. in their elongate form.
Fig. 5 has much shorter joints and may very possibly belong to a
different pair of maxillae. In this figure, the first joint is very
broad and large, subquadrate, tapering but little, rather longer
than broad, and bears apparently no curved process. Its edge is
spinose, fig. 6 6. The third, fourth, and fifth are, in figs. 5 and 8,

* Although the specimens from Church Hill look as if there were only a single process
to each joint, yet, as in the palpus of this species, figured in Plate XIII. fig. 11, there is a
pair of these organs, it is most likely all the other specimens had two. In this view the
two processes/ g, would belong to the terminal fifth joint.

BRITISH FOSSILS. 103

not very different in size and nearly square, while in fig. 7 the
proportions are longer. All have the great curved spines placed
about the middle of the joint.

In the perfect palpus (Plate XIII. fig. 9) the proportions of the
joints are as follows. The basal one is smaller than the second,
about two-thirds its length, and of a roughly triangular or trape-
zoidal shape, the base smallest. The second is longest — half as long
again as its breadth ; the third and fourth much shorter, the
fifth only half as long as broad, and bearing one curved spine at its
outer angle, and the other (g) at its tip. The second, third, and
fourth joints are subcylindrical, convex on their outer margin,
and bear the curved spines about the middle of the joint.

The terminal articulation (</), if it be a separate joint, consists
only of the curved process ; but it is probably only the opposite
spine of the fifth joint, seen obliquely, and in this view there would
be five joints only to the palpus, each joint bearing a pair of pro-
cesses, as is certainly the case in Plate XIII. fig. 11.

The processes themselves are directed obliquely outwards and
forwards ; they are long, curved, sabre-shaped, and much com-
pressed, fully three times as long as the width of the joints, to
which they are attached by a swelled base. They are striated
longitudinally, the striae, eleven or twelve in number, sharply im-
pressed, not continuous except near the tip, but interrupted alter-
nately (Plate XIII. fig. 10) for wide spaces, so that the number of
striae appears little more than half what it really is. Nor are the
striae quite parallel to the sides, for they abut obliquely against the
concave side towards the tip of the process. Here and there some
striae are stronger than the rest.

Near the base of the processes the striae are still more interrupted
and run into short impressed lines or puncta.

Plate XIII. figs. 5, 6, 7, 11, and 18.— These are from the UPPER
LUDLOW ROCK. Fig. 1 1 is a very perfect joint of the palpus, with
both spines attached ; and figs. 5 and 6 show the characteristic long
plicas ; fig. 7, part of a chela probably of this species. Fig. 6 at least
would answer best to one of the long joints of the antennae ; it is
but a cylindrical fragment of the proximal end, and has the
contraction which is visible in the corresponding joint of P. anglicus,
Plate IV. fig. 4 c. At this part the plicae are very numerous and
small; in the body of the joint they are large, prominent, and
elongate, and with the channel-like depression and its bounding
ridges, fig. 6a, magnified. They are somewhat unequal in size, and
set at more than their diameter apart from one another.

104 BRITISH FOSSILS.

Plate XIII. fig. 18. — There is one other fragment in the "Upper
Ludlow to which a place cannot be yet assigned, and yet belongs
apparently to P. punctatus. It is a long strap-shaped piece, two
inches and a half long and half an inch broad, and narrowed and
rounded at one if not both ends. At 6 it is imperfect. The sur-
face shows the peculiar long tubercular plicae of the species, at least
near the base (a) and the opposite end b, and the margins are
deeply incised by short slits forming nearly square serrations (like
those on the edge of the carapace of a crab). This is not exactly
the structure of any part of the margin of Pterygotus, the usual
ornament being that of prominent superficial plicae or tubercles.
The terminal (?) portion b differs in not having (so far as the impres-
sion shows) this serrate edge, but only a thickened crenate margin,
and is probably a distinct joint, or may even be accidentally placed
where it is. The surface shows elongate plicse of various sizes,
rather thickly scattered.

The Metastoma (Tlate XL fig. 4) is nearly three times as wide
as long, widest above the middle, and tapering backwards with
straight sides from this point to the blunt posterior extremity ;
the anterior end is broadest, rounded, and not even emarginate ;
much less bilobed as in other species. It is thus quite different in
•shape from that of any other species ; its long oval form, blunt
ends, and straightened sides enable us to recognize it at once. It
occurs three inches and a half long ; and in specimens of this size,
the width is one inch and a quarter.

The Swi/mmiTig Feet (Plate XL figs. 12-15) are very different in
proportion to those ofP.anglicus, the terminal joints occupying a con-
siderably greater length, and being abruptly wider than the rest. Of
the great basal joint (co in fig. 5) but little is preserved, but a larger
specimen, fig. 12, shows it to have been roughly squamose, especially
along its basal edge, the narrow squamae projecting as small spines,
the rest of the surface is closely imbricated with smaller plicse.
PI. XIII. fig. 14, is very possibly the serrate inner lobe of this joint.
The second joint b is large in proportion to the rest, and widens from
the base to its truncated apex. The third i is subtriangular, the blunt
apex of the triangle being anterior, and the edge articulating with the
next joint nearly straight or but slightly curved. The fourth joint,
on the contrary, is an obtuse triangle, of which the broad base is
forward and moderately arched, but not projecting as in P. anglicus.
It contracts rapidly behind, where it has a narrow deep notch to
receive the articulating process of the next joint. This, ca, is the
fifth, a remarkably short wide articulation, almost buried in the

BRITISH FOSSILS. 105

concave edge of the great penultimate joint, and curved to follow
the convex border of the triangular fourth joint. It is marked by a
strong transverse ridge. All these joints may be seen in figs. 5 and
13, but in a far less perfect state than in the fine specimen, fig. 13, pre-
sented by my young friend Mr. R. Lightbody, jun., of Ludlow. The
penultimate joint p is very large, nearly three inches long, and about
half as broad. It is oblong, with two rounded unequal lobes, and
deeply notched at each end (the distal notch at the end being the
deepest), so that the joint overlaps the proximate joints at either
end. The hinder margin of the joint is more convex at first, then
somewhat excavated, while the anterior margin is straight, or nearly
so : the hinder lobes at both ends are larger than the anterior
ones, the proximal one, which overlaps the small fifth and fourth
joints, being broader and rounder, and the distal one, which abuts
against the terminal palette, being long and narrow.

The terminal joint (d) is very long, nearly three inches by nine-
tenths of an inch wide, elongato-lanceolate, but rounded at the tip, its
anterior margin a little convex, and plain-edged half way down, the
posterior slightly concave and rather strongly serrate, — the serrae
are shallower on the anterior margin, and deepest round the tip.

Locality. — Church Hill, Leintwardine, in LOWER LUDLOW ROCK ;
Whitclifie, Ludlow, UPPER LUDLOW ROCK ; Kenda], Westmoreland ;
fragments in UPPER LUDLOW ROCK.

J. W. S.
January 22, 1 859.

[1.] H

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74 SE. Part of Shropshire, Montgomery, and Denbigh.

75 NW. Part of Caernarvon.

75 NE. Part of Caernarvon, Merioneth, and Denbigh.
75 SW. Part of Caernarvon.

75 SE. Part of Merioneth.

76 N. Part of Caernarvon.

76 S. Part of Caernarvon.

77 N. Part of Holyhead Island.

78 N W. N. part of Anglesea, and part of Holyhead Island.
78 NE. E. corner of Anglesea.

78 WS. S. of Holyhead Island and of Anglesea, with part
of Caernarvonshire.

78 SE. Part of Anglesea on Menai Straits, NE. of Caer-

narvonshire, and W. of Denbighshire.

79 NW. Part of Flint, Denbigh, and Caernarvon.
79 N E. Part of Flint, Cheshire, and Lancashire.

79 SW. Part of Flint, Caernarvon, and Denbighshire.

79 SE. Part of Cheshire, Flint, and Denbigh.

80 SE. Northwich.

80 SW. Chester, part of Cheshire.

81 NE. Part of Derbyshire and of the West Hiding of York

shire.

§1 SE. Part of Derbyshire and of N. Staffordshire.
2 NW. Chesterfield, part of Derbyshire.

82 SE. Mansfield.

82 S W. Chesterfield, part of Derbyshire.

N.B.— An Index to the Colours and Signs employed on the Geological Survey, price 5s.

The price of the Quarter Sheets is now uniformly 2s. 6d., with the exception of 57 N W . 76 N , and 77 N E . »

which are 1*.

LIST OP THE PUBLICATIONS OF THE GEOLOGICAL SURVEY, ETC. — continued.

HORIZONTAL SECTIONS,

Illustrative of the Survey's Geological Maps.

These Sections are drawn to a scale of six inches to a mile, horizontally and vertically, and describe in detail the Geologj
of the Country over which they are drawn. Descriptions are engraved on each plate, thus rendering each Section a coucisi
Report on the 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 coloured in accordance with the Maps. Sheets 1 to 55, price 5s. each.

VERTICAL SECTIONS,

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

These Sections are arranged, in the form of Vertical Columns, to a scale of 40ft. to an inch, and illustrate such details a
it is impossible to give in the Horizontal Sections above described. In the Coal Measure Sections, for instance, the Thicknes
of each Bed of Coal, the Mineral Structure and Thickness of the Strata with which they are associated, and the kiud am
Amount of Ironstone, are given in the greatest detail. Sheets 1 to 25, price 3s. 6d. each Sheet.

MAPS OF IRELAND.

On the one-inch scale.

WICKLOW includes Sheets 36 (NW., NF., SW., and SE.) and 41 (NW., NE., SW.)
WEXFORD includes Sheets 41 (NW.. NE., SW-, and SE.). 46 (NE. and SE-), 47 (NW-, NE., SW-, and SE.), 52 (NE.)

53 HW.and NE.)

WATBEFOBD includes Sheets 45 (SE.), 48 (SW. and SE.), 51 (N W., NE., and SE-), and 52 (NW-, N E-, and SW.)
Pi-ice 2s. 6d. each Quarter-Sheet.

BOOKS Published under the Superintendence of the Geological Survey and Museum of Practical Geology.

REPORT on CORNWALL, DEVON, and WEST SOMERSET. By Sir II. T. DE LA BECHB, F.R.S. &c. 8vo. 14*.
FIGURES and DESCRIPTIONS of the PALEOZOIC FOSSILS in the above Counties. By PEOFESSOB PHILUPS, F.R.J

8vo. (Out of print.)
THE MEMOIRS of the GEOLOGICAL SURVEY of GREAT BRITAIN, and of the MUSEUM of ECONOMIC GEOLOG-

of LONDON. 8vo. Vol. I. 21s. ; Vol. II. (in 2 Parts), 42s.
BRITISH ORGANIC REMAINS. Forminga portion of the Memoirs of the Geological Survey. Decades I. to IX., wit

10 Plates each. Royal 4to. 4s. 6d. ; or royal 8vo. 2s. 6d. each Decade.— Other DECADES are in the Press.

RECORDS of the SCHOOL OF MINES and of SCIENCE applied to the ARTS. Vol. I. Part I. Inaugural and IntroductOT
Lectures to the Courses for the Session 1851-52. Royal 8vo. price Is. 6d. cloth. Vol. I. Part II. On the Geology of tli
South Staffordshire Coalfield. By J. BEETE JUKES, M.A., F.R.S., £c. (2d Edition). Vol. I. Part III. On the Mines <

, , ..., .

Wicklow and Wexford. Ey WAMINGTON W. SMYTH, M.A., &<;. Vol. I. Part IV. Statistics of the Produce of Coppe
Tin, Lead, and Silver from the Mines of the United Kingdom, with the Exports and Imports of these Metals, froi
1848 to 1852 inclusive. By ROBEET HUNT, F.R.S., Keeper of Mining Records.

CATALOGUE of SPECIMENS in the Museum of Practical Geology, illustrative of the Composition and Manufactui
of British Pottery and Porcelain. By Sir HENBY DE LA BECHE, and TEENHAM REEKS, Curator. Svo. 1£
Woodcuts. Price Is. (Out of Print.)
A DESCRIPTIVE GUIDE to the MUSEUM of PRACTICAL GEOLOGY, with Notices of the Geological Survey of ih

United Kingdom, the School of Mines, and the Mining Record Office. By ROBERT HUNT, F.R.S. Price 6d.

A DESCRIPTIVE CATALOGUE of the ROCK SPECIMENS in the MUSEUM of PRACTICAL GEOLOGY. B

A. C. RAMSAY, F.R.S., Local Director, H. W. BBISTCMV, F.G.S., and H. BAUEBMANN. Price 6d. (2d Edition).

CATALOGUE OF THE CONTENTS OF THE MINING RECORD OFFICE. Price 6rf.

Memoirs of the Geological Survey and of tbe Museum of Practical Geology.

"MINING RECORDS." MINERAL STATISTICS for 1853-1854, embracing the produce of Tin, Copper, Lead, an

Silver for both years ; of Iron ; of Coals and other Minerals for 1854 ; tho Exports and Imports ; the Populatio

employed, and a List of the Collieries of the United Kingdom. By ROBEET HUNT, F.R.S., Keeper of Minin

Records. Price Is. 6d.
The IRON ORES of GREAT BRITAIN. Part I. The IRON ORES of the North and North Midland Counties of Enijlaui

(Out of print.) Part II. The Iron Ores of South Staffordshire. Price Is.
"MINING RECORDS." MINERAL STATISTICS for 1855 and 185fi, embracing Tin, Copper, Lead, Silver, Iron, Coals, Zin<

Salt, and other Minerals produced in the United Kingdom. 'Iheir Exports and Imports, ic. By ROBEET HUM:

F.R.S., Keeper of Mining Records. Price Is. Cd. each.

" MINING RECORDS." MINERAL STATISTICS for 1857. Pricels.M.
On the TERTIARY FUJYIO-MARINE FORMATION of the ISLE of WIGHT. By EDWAED FOBBES, F.R.S. Illu

trated with a Map and Plates of Fossils, Sections, &c. Price 5s.
On the GEOLOGY of tho COUNTRY around CHELTENHAM. Illustrating Sheet 44 by EDWAED HULL, A.B., F.GJ

GEOLOGY of PARTS of WILTSHIRE and GLOUCESTERSHIRE (Sheet 34.) By A. C. RAMSAY, F.R.S., F.G.S
W. T. AVELINE, F.G.S., and EDWAKU HULL, B.A., F.G.S. Price 84.

These Maps, Sections, and Books may be obtained at the Museum of Practical Geology,
Jermyn Street, London.

A'.L.-To prevent the confusion arising from different titles, as above, all further publications will appear under fli
general title of "MEiioitts OF THE GEOLOGICAL SUBVEY, and of tho Museum of Practical Geology," the icoro
" Monograph*," " Decades," " Mining Records," " lleports" d~c. behiy employed as subordinate titles, as in the leu
works of the Uit.

Jan. 12,1859. RoDEBiCK I. MrEcnisoN, Director-General.

f • v .