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I.—ON THE GAMPSONYCHIDA, AN UNDESCRIBED FAMILY OF FOSSIL
SCHIZOPOD CRUSTACEA. PL. TU, FIGS. 1-4; VIL, FIGS. 1, 2.

READ APRIL 21, 1855.

By A. S. PACKARD.

The opportunity of examining at my leisure about a dozen specimens of Palcocaris typus of
Meek and Worthen, kindly afforded me by Messrs. R. D. Lacoe and J. C. Carr, has enabled me to
work out some characters of this genus not mentioned by the original describers. The study of
these specimens has induced me to compare the genus with Gampsonyx, and the result has led to
the formation of a family or higher group for the genera, which should probably stand at the base
of the Schizopoda, while also serving to bridge over the chasm existing between the Thoracostra-
cous suborders, Synearida and Schizopoda. !

Paleocaris was first described by Messrs. Meek and Worthen, in the Proceedings of the
Academy of Natural Sciences of Philadelphia (1865, p. 48), from specimens occurring in clay-stone
concretions in the lower part of the true coal measures, at Mazon Creek, Morris, Grundy County,
Illinois. Afterwards,in the third volume of the Reports of the Geological Survey of Tlinois, 1868,
the same authors figured the fossil, and expressed themselves as follows regarding its affinities:
“Hence it would seem to present something of a combination of decapod (macrouran) and tetra-
decapod characters. That is, it possesses the caudal appendages, anteriorly directed thoracic legs,
the antenne (some of the specimens appear, also, to show basal scales to the outer antenna) and
general aspect of a macrouran, with the distinct head, divided thorax (without a carapace), and seven
pairs of thoracic legs, of a tetradecapod. We have not been able to see its eyes, but from its other
decapod characters, and its analogy to Gampsonyx, which is said by von Meyer to have pedun-
culated, or at any rate movable, eyes, we are strongly inclined to believe that our fossil will be
found to agree with Gampsonyx in this character also.

“Tt therefore became a matter of interest to determine to which of the subclasses, Decapoda or
Tetradecapoda, it really belongs. That it belongs rather near Gampsonyx, though not to the same
subordinate section (Schizopoda), there can be little doubt. Hence these two forms apparently fall
naturally into the same family. Professors Jordan and von Meyer seein to have regarded Gamp-
sonyx as a Tetradecapod, connected with the Amphipoda, but also possessing macroural decapod
aftinities. Professor Dana, however, regards it as a low type of Macrura, belonging to the section
Schizopoda. He and Dr. Stimpson, to whom we sent sketches of our better specimens of Paleo-
caris, concur in the opinion, judging from all its characters yet known, that it is a low embryonic
type of the Macrura, in which the carapace is not developed.

1 We have not seen Burmeister’s memoir ‘‘ Ueber Gampsonychus” (Abh. d. naturf. Ges. in Halle, ii, LOL, 1855),
but Zittel (Handbuch der Paleontologie, p. 670) quotes Burmeister as stating that he regarded it ‘'as the representa-
tive of a special group of Crustacea, which unites in itself some of the most essential features in the organization of
the Stomapoda and Amphipoda.”

S. Mis. 154——17 129

130 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

“Generically, it is separated from Gampsonyx, figures of which (cuts C and D) we have added
for comparison, not only in the nature of its caudal appendages, but in the more important char-
acter of having its thoracic legs simple, and not bifid, as in the Schizopoda.”

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Fic. 1.—Gampsonyx fimbriatus. After Jordan and von Meyer. From Meek and Worthen.

We will now describe in detail Paleocaris typus, restoring it so far as possible in our description
from the specimens received from Messrs. Lacoe and Carr, amounting in all to about a dozen, of
which ten were kindly loaned by Mr. Lacoe. Dr. Kingsley has also obligingly drawn a restoration
of the fossil from the specimens sent him for the purpose. There are no traces of a carapace, but
the head is plainly distinet from the rest of the body. It is rounded in front, with no traces in my
specimens of a rostrum, and is apparently composed of two segments. The body, seen sidewise, is
suddenly arched or bent at the articulation of the thoracic and abdominal regions, as in stoma.
pods and shrimps, and of the usual proportions. All the segments behind the head are free, and
are fourteen (seven of which are abdominal) in number, counting the telson as one. There are
thus sixteen segments, the head composed of two, the thorax of seven, and the abdomen of seven.
The body thus has apparently the same number of thoracic and abdominal segments as in the
existing Stomapoda. It is probable that the head of Palwocaris is composed of the same number
of segments as in the Schizopoda, but as the mouth parts have not been preserved, this point must
remain undetermined. The thorax, in its general shape, as seen from above, is of the normal shape,
as seen in existing Stomapoda. The abdomen is much narrower than the thorax, with the basal
segments short, and the penultimate one longer than broad, widening out a little on the hind margin,
and excavated behind to receive the base of the telson.

The first antenne are about one-half as long as the body, with the scape long and slender,
three-jointed (unless what I regard as the basal joint consists, as appearances suggest, of two);
first joint long and slender; second, as thick but only one-halfas long as the first; third, moder-
ately long, considerably longer than the second; flagella nearly equal in size, long and slender.

The second antenne with the scape three-jointed, the basal joint long; second and third, of nearly
the same size and length; flagellum thick at base, long and slender, entire antenna nearly half as
long as the body of the animal.

Of the thoracic feet, six pairs can be detected, while in front of the first pair are two other
appendages like thelegs, but whether they are gnathopods, like those of other Schizopoda, or thoracic
feet, it is difficult to judge. Each thoracic foot is long and slender, the three distal joints forming
the greater part of the limb. The terminal (seventh ?) joint is very long and slender, and probably
ends in @ single claw. The penultimate joint is about two-thirds as long as the terminal. It is
thickened towards the end, and is perhaps a little shorter than the third joint from the end.

The endopodites* are distinetly preserved ; those on the last four pairs of legs are long, narrow,
lanceolate-oval, acute at the end, each side of the endopodites being alike, 7. ¢., one not being more
convex than the other. If extended, the endopodite would reach out to near the middle of the
terminal joint of the limb. I think I can detect eight pairs of endopodites—six at least— one on
each thoracic leg and one on each of the gnathopods, if such they are. This would tend-to show
that the first two appendages behind the head are true gnathopods, like those of existing Schizo-
pods, especially Petalophthalmus.

There are traces of a pair of abdominal legs to each of the seven segments. To the rather

“Thad regarded these appendages as breeding lamellw, but Dr. Kingsley suggests that they are endopodites, and
though the joints are very indistinct, I am disposed to accept his correction, and will speak of them as endopodites.
We should, on general grounds, regard them as endopodites

{ON THE GAMPSONYCHID A. 131

thick and long basal joint of each were probably attached two slender rami. ‘The entire limbs
were about one-half as long as the thoracic legs (see Lacoe’s No, 404°). There were at least five
pairs (and | think traces of a sixth) besides the last pair. The end of the abdomen, with the telson,
and last pair of legs are as’described and figured by Meek & Worthen. The telson is large in
size, broad and short, somewhat triangular, being broader at the base than at the end. It is some-
what spatulate in form, being well rounded at the end, and much shorter than the inner rami of the
appendages associated with it. Its end is fringed with coarse sete. In the last abdominal ap.
pendages, the outer ramus is broader than the inner, with a deep longitudinal crease, or impressed
line, which fades out on the onter third, or extends to the end of the basal joint. The second, or
distal joint, is fringed with fine sete. The suture between the two joints is externally indicated by
two sete larger than the others, and somewhat curved. ‘The inner ramus is somewhat shorter than
the outer; the end well rounded, and fringed with sete. It reaches to the second joint of the
longer outer ramus.

Total length of the largest specimen 33™™.

Total length of the best preserved specimen 25™™ (Lacoe’s No. 404°), This specimen gave us
the following measurements :

Length of Ist antenne (estimated) 8™™.

Length of 2d antenna (estimated) 10-11™™,

Length of last thoracie leg (exopodite) 8™™.

Length of endopodite 4™™,

Length of telson 3™™; width 1.5™™,
Length of outer ramus of last pair of abdominal feet 4™™.

It should be observed that the endopodites are in part represented in Meek and Worthen’s
figure, but not referred to in their description. They are also partly represented in their copy of
Jordan and von Meyev’s figure of Gampsonyx fimbriatus. Inthe latter, there is also present what is
apparently a large, coarsely spined, mandibular palpus, somewhat like that in the male of the exist-
ing deep-sea Schizopod Petalophthalmus armatus described by Willemoes-Suhm.* In the females,
however, the palpus is small and unarmed. In the figure of Gampsonyx referred to, the thoracic
legs themselves, irrespective of the endopodites, are represented as biramous, and the two rami are
drawn as of nearly equal length. It is probable that there has been a mistake in drawing the
legs, as in none of the existing Schizopods, such as Mysis and its allies Euphausia, Gnathophausia,
Petalopthalmus or Chalaraspis, are the legs thus thrice divided. It is to be hoped that the fossil
itself will be examined anew with regard to this important point.t

It is sufficiently evident, however, that Gampsonyx and Palgocaris are closely allied forms, and
as first suggested by Messrs. Meek and Worthen should fall into the same family, which may be
called Gampsonychide. ‘Lhe principal character which separates this group from all other Schizo-
pods is the entire absence of a carapace.

It is worthy of notice, however, that the size of the carapace is very variable in the Schizopods,
and in the genus Petalophthalmus there is a great discrepancy in the two sexes. In the female it
covers the entire thorax, while in the male it is remarkably small, subtriangular, leaving the two
hinder thoracic segments entirely exposed, as well as the sides of the two segments infront. Inthe
large size and oval-lanceolate shape of the endopodites, both of the gnathopods (maxillipedes)
and thoracic feet, the Gampsonychide‘agree with Petalopthalmus, in which they are large and broad.
In the shape of the telson and the comparative size and proportions of the last pair of abdominal
appendages there is a close relationship in the Gampsonychide to the Schizopod genera Petalo-
phthalmus and Chalaraspis, especially the latter genus, in which the telson is rounded at the end,

*On some Atlantic Crustacea from the Challenger Expedition, by Dr. R. von Willemoes-Suhm. Linnean Trans-
actions. Zoology, vol. i, p. 28, 1874.
+No light is thrown on the nature of the limbs by the thirty specimens of Paleocaris scoticus described by Mr.
B.N. Peach trom the lower Carboniferous rocks of Scotland. Nor were eyes with certainty detected in his specimens.
“ For instance, although in most of the specimens there occur small oblong bosses just in the place where their eyes
should be, were they decapods, figs. 10-10d, yet the facets of the cornea have been looked for in vain. This is unfor-
tunate, as it prevents one from saying with certainty that these are the eyes, though there is a strong presumption in
favor of their being so. No sessile eyes have been observed on the carapace, neither has a trace of anything been
observed that could be construed into such.”—Trans. Roy. Soc. Edinburgh, 1882,"p. 86.

132 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

while the two rami are more as in Petalophthalmus, though broader. The other biramous abdominal
appendages in the Gampsonychide are truly schizopodal.

Fic. 3a.—Telson of Peta-
lophthlamus¢.

Fic. 3.—Petalolphthalmus armatus<.
$

Fic. 4b. — Third
perce of Peta-
ophthalmus 9.

Fic, 4.—Petalophthalmus armatus?. This and Fig. 3 after W.Suhm.

Fic. 4a.— Second gna-
thopod of Petalophthalmus
9. 1, breeding lamella.

Classifying the Schizopoda by the carapace, modifying Willemoes-Suhm’s table by throwing
out the Nebaliadew and substituting the Gampsonychida, there would seem to be three groups, as
follows:

Ly Oarapace absent :--< Sars kocsis s toh San seme wele nates eiciae eee Seen aieecemaan aaen wenn ane (Gampsonychide).
Il. Carapace free, varying in 81z6_-- << 22 scase sere cena ee eee (Gnathophausia, Petalopthalmus and Chalaraspis).
TIL. Carapace fastened. to the thorax: 5222-- en. -se eee oe one ee aes (Mysis, Lophogaster and Euphausia).

But I should agree with Willemoes-Suhm that this is not a natural genealogical classification,
and throwing out the Nebaliad, which, as we have endeavored to show, belong to a distinct order
of Crustacea, the families of Schizopods may be enumerated thus (after adding the Gampsonychide
to von Suhm’s table), all having seven abdominal segments :

Carapace absent, six pairs of thoracic legs... 60.2. - cons sec ncs cence sascwsevsweccnce=se=nesesaess I Gampsonychida.
Carapace well developed, six pairs of thoracic legs... ooo. coco ek ncn s cece womens eon eesnesnesse Il Myside.
Carapace well developed, eight pairs of thoracic legs..........-..---- ------ --- 20+ eee eee eee eee Il Euphausiide.
Carapace well developed, four pairs of thoracic legs...... 2.22... 222+ 22-2 eee ee een ne eee eee eee IV Chalaraspide.
Carapace well developed, seven pairsof thoracic legs:........----.--------+- +--+ seee-+----------V Lophogastrida.

When we compare the Gampsonychidw with the Synearida (Acanthotelson), we see that both
groups have the same number of body-segments, and that both lack a carapace; and thus, while
the Gampsonychidw are the ancestors of living Schizopods, the group as a whole probably de-

ON THE GAMPSONYCHIDZ. $33

scended from Acanthotelson, which is thus a truly synthetie form, standing in ananeestral relation

to all the Thoracostraca, while it also suggests that the sessile-eyed and stalked-eyed Crustacea
may have had a common parentage.

Explanation of Plate III."

Fig. 1. Palwocaris typus, M. & W. restored, enlarged four times. (The front of the head is partly conjectural
and though stalked eyes probably existed, no attempt Las been made to restore them. )

Fig. 2. Palwocaris typus, seven thoracic segments, showing the disposition of the endopodites, x8 (Lacoe’s 404D).

Fig. 3. Palewocaris typus, dorsal view of one side of three thoracic segments, showing the basal joints of the en-
dopodites (endop), and exopodites (erop), enlarged.

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HI—ON THE ANTHRACARIDA, A FAMILY OF CARBONIFEROUS MACRU-
ROUS DECAPOD CRUSTACEA.

READ APRIL 21, 1885.

By A. 8. PACKARD.

Having been kindly favored by Messrs. R. D. Lacoe and J.C. Carr with the opportunity of
examining their collections of nodules from Mazon Creek containing Anthrapalamon gracilis Meek
and Worthen, I have been able to discover some features probably not shown in the specimens
examined by Messrs. Meek and Worthen. The newly observed characters are the carapace with
its rostrum, showing that the American species in these respects closely resembles the European
ones figured by Salter, the founder of the genus. Moreover, our specimens prove the existence of
five pairs of thoracic legs, while the antennae of both pairs are almost entirely shown. The fact
that the first pair of thoracic feet were scaicely larger than the succeeding pairs, suggests that
Anthrapalemon cannot be placed in the Eryonidie, but should form the type of a distinct group of
family rank, none of the existing Macrura, so far as we are aware, having such small anterior
legs. Other characteristics which we ahall point out confirm this view.

The genus Anthrapalemon, a Carboniferous fossil, was first described by J. W. Salter in the
Quarterly Journal of the Geological Society of London (xvii, 529, 1861), The name given to the
fossils has, the author remarks, ‘only a general signification, and is not intended to indicate a
real relation to Palemon.” He also remarks that ‘‘the genus is not to be confounded with any of
the Liassic or Oolitic ones published by von Meyer, Miinster, &c. . . . It is broader than the
general form of the Astacidie, or than Glyphea and its Liassic allies, but much narrower than Hryon.”
Salter’s type-species is Anthrapaleamon grossarti Salter.* With this species the American A.
gracilis is congeneric. A closely allied English form, A. dubius Prestwich, is referred by Mr. Salter
to the subgenus Palwocarabus, a name even less fitting than Anthrapalemon. Concerning the
other form provisionally referred to Antbrapalemon by Mr. Salter (his Fig. 5), we will remark
in a supplementary note to this article.

The only American species we have seent is Anthrapalemon gracilis Meek & Worthen, first
described in the Proceedings of the Academy of Natural Sciences of Philadelphia, 1865, and

_ redescribed and figured in the second volume of the Geological Survey of [linois, and again in

the third volume.

Mr. Salter figured the carapace aud rostrum, as well as the abdomen of the European species ;
while the specimen figured by Meek and Worthen evidently did not possess the carapace, but
showed perfectly the telson and neighboring pair of abdominal appendages.

The specimens loaned us by Mr. Lacoe enable us to give a more perfect description and illus-
trations of this important type; and I am indebted to Dr. J. 8. Kingsley tor the restoration and

*In his Handbuch der Palieontologie, Zittel mentions Pseudogalathea Peach, from the carboniferous of Scotland.
We have not yet seen Mr. Peach’s article.
tDr. J. W. Dawson has described and figured, the carapace of Anthrapalamon hillianum, from the Carboniferous
of Nova Scotia. Geol. Mag., iv, new ser., p. 56, fig. 1, 1877. Also figured in his Acadian Geology, 1878.
135

136 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

details, which he has so faithfully drawn. I am inclined to think that the body was actually
broader than Dr. Kingsley has drawn it, and that tlie lateral spines of the carapace were visible
from above; but I leave it as an open question.

The carapace is of the same length as the urosome (abdomen) or slightly longer, being from
two-thirds to three-fourths as wide as itis long. Itis very thin and delicate, and many specimens
have none. The sides are regularly curved, and unarmed behind the middle, but on the anterior
third are seven distinet, sharp lateral spines, the seventh being three times as large as the others
and situated on the anterior outer angle of the carapace. I cannot with certainty distinguish any
spines between this last-mentioned spine and the rostruin.* Casts of the latter are distinctly seen
in two specimens (Lacoe’s 200pp and 200mm) to be small, triangular, short, and acute. The
rostrum itself is pretty well preserved in one specimen (Mr. Lacoe’s No. 200)). It is rather long,
stout, strong, acute, situated between the first antenna, and extending as far as the middle of the
third joint of the scape of the latter. In another specimen (Lacoe’s 20000, 200nn) the rostrum is
fairly well preserved ; it is long and slender, and about half as long as the carapace; also as long
as the abdomen is wide in its narrowest part.

In only a single specimen is a side view of an apparently folded carapace preserved. The
entire rostrum is long and straight, slender and acute, originating in the anterior third of the
carapace, the entire rostrum being about half as long as the carapace itself. (Pl. VII, figs. 3. 3a.)

Along the sides are numerous sharp spines. Whether there was, as in the other form (A.
grossarti), a series of dorsal spines our specimens do not distinetly show. Behind the base of the
rostrum a median ridge extends to the posterior edge of the carapace. The lower edge of the
carapace is serrate on the anterior third, as in all the other specimens. On the surface of the
carapace an apparently false or superficial suture passes out laterally from the anterior third, and
another impressed line, better marked, from the posterior third, extending half-way to the edge
of the carapace. The surface of the carapace is seen to be finely shagreened, but scarcely tuber-
culated, as in the European A. grossarti.

Of eyes no traces are visible in any of the specimens except one, and Iam inclined to the
opinion that they were either wanting or very small, and concealed under the front edge of the
carapace. At the same time it should be observed that in none of the fossil macrurous Crustacea
from the Carboniferous are the eyes preserved. It may also be borne in mind that in the deep-
sea Pentacheles sculptus 8 vith no corneal area was to be detected, and in Willemesia and the fossil
Eryoniscus the eyes are entirely wanting.t So far as we can decide, the front edge of the carapace
is not excavated at ‘.e point where we should look for eyes or eye-stalks, but, on the contrary,
seems to be quite regularly convex. Still, additional specimens are needed to clear up the exact
nature of the front edge of the carapace.

In most of the specimens the thin, delicate carapace has not been preserved. When it is
absent the five thoracic segments are distinetly marked, of about the same length. In front of
these are three cephalic segments, making eight segments in all apparent in some specimens.

The first antenne are large and long; the scape three-jointed, first joint long, the second about
one-half as long as the first and of about the same width; third joint a little longer, but smaller,
than the second; the two flagella are a little longer than the scape, the inner one about half as
thick and evidently only half as long as the outer one. (Lacoe, No. 2007.)

The second antenne are, with the scape, considerably stouter than those of the first pair; first
joint short and stout, but longer than broad; second very short, oblique at the end, and consid-
erably shorter than the third joint, which is about as long as thick; the flagellum is very long and
slender, multiarticulate, at least as long as the carapace, and directed back ward, as in Pentacheles;
there is an antennal scale present, but its outlines are very indistinct.

The five pairs of legs are preserved (Nos. 200pp, 200"); they are all of nearly equal size, the
first pair apparently being no larger than tie others, in this respect differing from Galathea and the
existing Galatheidea, Of the first pair of limbs there are in one specimen (200d) traces of nearly

* Dr. Kingsley has, however, detected a spine at this point and inserted it in his drawings, as seen in the plate,

t After this paper was written the specimens were sent to Dr. Kingsley to be drawn; among them the specimen
with traces of an eye. He has drawn in the eye; and on examining the specimen again, I think that he is right in
representing the eyes. It was apparently large and well developed.

aly

ANGLIA AD
My
1G. 6a.—Eumunida picta, end of abdomen enlarged.

va

Fic. 7.—Anoplotus politus Smith.

RECENT DEEP-SEA GALATHEIDEA. After S, I. Smith.

S, Mis. 154—To face page 137. .

ON THE ANTHRACARID A, ikaw

the entire limb, @. e., at least the first and second joints; the third joint could not have been of
large size, a feature distinguishing the Bryonidze as well as Astacids and the higher Macrurans
in general. The first and fifth pair seem to be of about the same size; the third and fourth pair
of legs are a little larger than the others and but little longer than the width of the carapace. — It
is untortunate that uo specimens have yet been found with the first pair of limbs entire, but the
fact that the two basal and perhaps the third joints are no larger than those of the other pairs of
feet indicates that this form differed from all the fossil and recent Eryonidi, and is a character of
so much importance as to forbid our regarding Anthrapalemon as a member of that family; the
only other alternative being to consider if as a type of a distinet family. Of the four hinder pairs
of legs the three terminal joints of the limbs (these affording the diagnostie characters) are pre-
served, and the proportions are much as in the four hinder pairs of thoracic legs of the existing
deep-sea Pentacheles; of the three joints the proximal and middle ones are long and slender, the
inner one longer than the outer of the two; the distal (terminal) joint is rather short and pointed,
and apparently chelate. Meek and Worthen remark that the legs are not divided; whether they
meant that the legs are not divided as in the Schizopoda, or simply referred to the terminal joint
alone, does not appear, but in the specimen before us (No. 200pp) the last joint appears to he
chelate, since what seems to be the smaller inner finger is partly but tolerably well preserved, the
crust or derm itself being preserved. Yet we may be mistaken.* In Meek and Worthen’s figure,
the terminal joints are drawn as undivided. If this is the case, they resemble the four hinder
legs of Munida, Eumunida, and Anoplotes.

The abdomen is rather short and broad, as in the Galatheide, and consists of seven segments,
counting the telson as the seventh.

The general appearance and relative size of the telson, together with the last pair of abdominal
appendages, is much as in the Eryonidie, with some important differences. The telson, unlike that
of any other Macruran, fossil or recent, so far as [am aware, is differentiated into three portions ;
the basal central piece is somewhat polygonal, a little longer than broad; it is separated by a
distinct suture from a small triangular terminal piece which forms the apex of the telson. Between
the outer half of the entire telson and the inner ramus of the uropoda is a large broad lobe which
is fringed with sete. At first ] regarded it as a subdivision of the inner lobe of the last uropoda or
abdominal feet, but no instance among the Decapoda is known to us in which the Jast pair of
uropoda have more than two lobes or divisions, and I have therefore been inclined to associate the
innermost of the three setiferous lobes with the telson, and to regard the telson as divided into
two median and two lateral lobuiar setiferous portions. Whether the two lobes belong with the
telson or uropoda I will leave for the present an open question. The only group in existence in
which the telson is so remarkably differentiated is the Galatheidee. In Munida the telson is
divided by sutures into four pieces, the two terminal ones lobate and edged with setie of the same
size as those of the uropoda. In Eumunida of Smith the telson is “short and broad, more or
less membranaceous, and divided by a transverse articulation, so that the distal part may be
folded beneath the basal part.” In Anoplotus politus, like the foregoing, a deep-sea Galatheid,
“the telson is stiffened by eight distinct calcified plates; a broad median basal plate, with a small
one on either side at the base of the uropod, and a small median one behind it, and between a pair
of broad lateral plates, still behind which there is a second pair, which meet in the middle line and
forin the tips and lateral angles.” Professor Smith’s figures of Munida, Eumunida, and Anopotus
are here reproduced from electrotypes kindly loaned by Professor Baird, U.S. Fish Commission.t

From the nature of the differentiation of the telson in the Galatheidee [ am inclined to believe
that the telson of Anthrapalemon is subdivided in somewhat the same manner. If so, we cannot
refer the genus to the Eryonid, and we would therefore regard it as the type of a distinet family
which may thus be briefly characterized :

Family Anthracaridw: Body rather broad and slightly flattened ; first antennw with two long
— *In none of the six Scottish Carboniferous species of Anthrapaliemon described by Mr. B. N. Peach, do either of
the thoracic limbs appear to be chelate.

t Preliminary report on the Brachyura and Anomura dredged in deep water off the south coast of New England,
by the U. S. Fish Commission, in 1880. By S. I. Smith, Proce. U.S. Nat, Museum, 1883, June 18.

S. Mis. 15418

138 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

flagella; second antenne long, without a seale; the first pair of thoracie legs no longer than the
four succeeding pairs; the fifth pair of legs as long and well developed as the others; carapace
ovate, smooth, without transverse impressed lines, with a long, acute rostrum; with lateral spines
on the anterior half; abdomen rather broad, nearly as much so as the carapace; the telson broad
and differentiated into two median pieces, the basal piece with broad, rounded membranaceous
lobes, one on each side, fringed like the two rami of each uropod, with long sete.

After the foregoing paper was written, and an abstract published in the American Naturalist
for September, 1885, I sent the specimens to Dr. Kingsley to be drawn, and on their return he
made the following criticisms, which are here quoted :

“From the characters shown in the specimens before me, Anthrapalemon apparently has
nothing to do with the Eryonidw, but belongs rather to the Schizosomi of Stimpson. The thoracic
structure, antenne, sternum, and telson are all paralleled in that group. The telson is much like
that of the Porcellain crabs. The absence of the distal pedal joints of the legs renders its family
uncertain. It may belong to some of those existing in the fauna of to-day. It certainly shows no
features which would justify the creation of a new family for it.”

While I should hardly agree with the view that Anthrapaleemon belongs to the Schizosomi,
since Porcellana is a brachyuran, with a broad, round cephalothorax and small abdomen,
folded beneath the body, the differentiation of the telson is some what as in Porcellana, —=
as will be seen by reference to Fig. 7, copied trom Milne Hdwards.* On the other hand, I
have erred in regarding it as closely allied to the Eryonida, as defined by Zittel in his Wi
Handbuch der Palaeontologie. Having already drawn attention to the highly differen- | Fre.7.—
tiated telson of the Galatheidee, | am now much inclined to regard the Anthracaridze Abdomen
as more nearly related to this group. The resemblance to the Galatheidie is seen in the °! Percel-
general shape of the body, the proportions of the carapace with its sharp rostrum, and leue
the proportions of the abdomen with its broad telson and uropoda. The firsf pair of antenne differ,
however, from those of the Galatheidiw in having two well-developed flagella, and the first pair of
legs are much smaller, while the fifth pair are larger in proportion; the last pair of uropoda are
more as in the Glypheide and Astacidi, the outer ramus being divided into a long basal and short
broad distal segment.

It seems to us, from what we now know of the characters of Anthrapalieemon, as we have
worked them out, that it cannot be placed in any known family of Decapoda. We should now be
inclined to place the Anthracarid:e nearest the Galatheidee, most of which are deep-sea forms.
It is not improbable that they were the forerunners or ancestors of the Galatheidie.t That the
family is a synthetic group is shown by the resemblance of its telson to that of Porcellana, a
3rachyuran. It certainly does not belong among the Palinuridee, nor, on the other hand, among
the Glypheide.

In Zittel’s valuable Handbuch der Palwontologie (Bd. 1, 2d Abth., Lief. iv, p. 682), Anthrapa-
lemon is placed among the Peniwidie, but its characters appear to be such as to forbid such an
alliance. Paleontology is an inexact science, but the attempt to seek the natural position of
extinct forms leads us to examine their remains more closely, to make further explorations for
more perfectly preserved specimens, while the final resuit is to lead us to enlarge our concep-
tious as to the affinities of existing types of life. It seems to us better to establish new groups for
Paleozoic forms of uncertain positions than to crowd them into groups of highly specialized
modern forms. Yet this tendency may be carried too far. Whether we have erred in the present
instance we leave to the judgment of those who, with a special knowledge of modern Crustacea,
also possess both critical skill and broad views in dealing with natural groups.

Nore ON THE PALAOzOIC SHRIMPS (Caridide).

The form provisionally referred to Anthrapaleemon by Salter (his fig. 5, Quart. Journ. Geol.
Soe. London, xvii, 1861), occurring in the Carboniferous beds at Lanarkshire, Scotland, which has

*Crustacés, pl. 22, fig. 7.

| After writing the foregoing remarks I found I had overlooked Professor Dana’s opinion, expressed on p. 350 of
his Manual of Geology, 3d edition, where, after referring to the British species of Anthrapalemon, he adds, ‘“ but the
broad flattened carapax indicates a nearer relation to Aiglea and Galathea than to Paleemon.”

ON THE ANTHRACARID®. 139

been copied into geological text-books as representing Authrapalemon (see Dana’s Manual of
Geology, fig. 686 A), does not belong to that genus or the group it represents, but is evidently
one of the true shrimps or Carididie. The carapace and serrated rostrum, as well as the shape of
the abdomen, the form of the last pair of uropoda, and the telson, all indicate genuine prawn-like
affinities. It may be named Archicuris salteri.

The other Carboniferous shrimps are Crangopsis soliates (Salter, Quart. Journ. Geol. Soc. 533,
fig. 8, 1861). This appears to be a genuine Caridid; it is from the subcarboniferous beds of
England. (As synonyms of Crangopsis Salter are Palwocrangon Salter, non Schauroth, and Ure
nectes Salter. (See Zittels Paleeontologie.)

Pygocephalus cooperi, of Huxley, from the Carboniferous beds near Manchester, Hugland, is a
doubtful form, which he refers ‘either to the decapodous or stomapodous group of the class.’
(Quart. Journ. Geol. Soc., xiii, 363, 1857; xviii, 420, 1862). Professor Dana (Manual of Geology,
3d_ edit., p. 350) regards this form as a Schizopod.

No Carboniferous Carididie have as yet been discovered in America. The oldest known
macrurous Crustacean, however, is American, the Palwopalamon newberryi, described by Mr. Whit
field (Amer. Journ, Se., 33, 1880), from the Upper Devonian of Ohio.

Explanation of Plate IV.

Fig. 1. Anthrapalwmon gracilis, M. & W., restored, enlarged 5 times.

2. cn i) a carapace and eyes, X j.

3. be ee ee carapace flattened, seen from above x 34.
4 i Ly Hf part of first thoracic leg, x 4.

Ly, Uh LG ML four basal joints of the fifth leg, >< 4.

6. es - a telson and last pair of uropoda, x | to 4.

All the figures on this plate drawn by Dr. J. S, Kingsley.

MEMOIRS NAT. ACADEMY SC,,VOL. III

PLATE IV

(" :

xa * = i Ae toe \ " y\)
NY AN Ii

J S.Kingsley, del. a : ; Julius Bien & Co. lth

ANTHRAPALA-MON GRACILIS.

WFAN 197

NATIONAL ACADEMY OF SCIENCES.

WO ia. LT.
FIFTEENTH MEMOIR.

ON THE SYNCARIDA, A HITHERTO UNDESCRIBED SYNTHETIC GROUP
OF EXTINCT MALACOSTRACOUS CRUSTACEA.

S. Mis. 154——16

EC

a. Pe BAY cot

L—ON THE SYNCARIDA, A HITHERTO UNDESCRIBED SYNTHETIC GROUP
OF EXTINCT MALACOSTRACOUS CRUSTACEA. PLS. I, IL

READ APRIL 21, 1885.

By A. §S. PACKARD.

For a long time I have been desirous of examining into the relationship of the singular group of
Carboniferous Crustacea represented by the genus Acanthotelson of Messrs. Meek and Worthen, as
it has seemed to be a remarkable connecting link between the Edriophthalmata (or Tetradecapoda)
and the Decapoda (in the older sense). An unexpected opportunity has been offered in a large
series of specimens, which, without solicitation on my part, has been generously offered me by
R. D. Lacoe, esq., of Pittston, Pa., and J. C. Carr, esq., of Morris, Ill. Mr. Lacoe’s collection was
a very rich one, comprising over forty nodules, each containing a usually well-preserved Acantho-
telson. Although additional specimens are much to be desired, especially such as may show the
eyes and their nature, whether sessile or stalked, a point still unknown, the eyes not having been
with certainty identified, and also to better show the nature of the abdominal appendages, it seems
to us that enough characters have been preserved to allow us to present a tolerably accurate
account of the essential features of the group.

The genus Aeanthotelson was first proposed by Messrs. Meek and Worthen, in 1860,! and the
species described as A. stimpsoni M. & W. A second species, A. eveni, was described by the same
authors in 1868.% Additional facts were stated and figures given in the Report of the Geological
Survey of Illinois, III, Paleontology, 1868. The specimens we possess enable us to amend and to
add to their original descriptions; but in doing so we wish to bear witness to the care and ability
displayed by the authors in the examination and illustrations of this form. The genus is referred
with doubt by the authors to the Isopoda, who also refer to its resemblance to some of the lower’
types of macroural Decapods. They remark: “ From all the specimens of this genus now known
it is evident that, in the nature of its anteunie, as well as in the forward direction of all its thoracie
legs, and to some extent even in the nature of its caudal appendages, it differs from the Tetra-
decapoda, and approaches some of the lower types of the macroural Decapoda. In the possession
of seven distinct thoracic segments, without a carapax, however, as well as in the form of all its
thoracic and abdominal segments, it agrees with the Tetradecapoda, particularly with the Isopoda,
which have but one pair of the abdominal appendages styliform, instead of three, as in the
Amphipoda. One specimen of A. stimpsoni (represented by fig. B, p. 549) also appears to show
the eyes (marked I in the cut) to be sessile, though remarkably prominent. If they are sessile, this
must be conclusive evidence that it must be a Tetradecapod. Until other examples, showing more
clearly the nature of its eyes and some other parts, can be examined, we leave it provisionally
where we first placed it with doubt, in the Isopod group of the Tetradecapoda.” (P. 550.)

The following Sescup tion, while embracing the more general chee ous C a of the Sette to

a Prceediige ade my of Natural Sciences, Philadelphia.

2 Amer, Journ, Sc., 2d ser., xlvi, 28, 1868.
123

124 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.
which Acanthotelson belongs, also without doubt comprises the generic and specific characters.
We will first give a description of the fossils themselves, based on the material we have had for
examination, and then endeavor to point out those characters which we suppose to be the essential
features of the group to which the genus belongs, and also to indicate the probable affinities to
the other divisions or suborders of Malacostraca. It may be as well to say that, after examining
some forty specimens, we are unable to distinguish between Acanthotelson stimpsoni and event, and
are inclined to believe that the former is the young of the latter species.

In Mr. Lacoe’s No. 501) the head is well preserved; the first arthromere or segment is considerably
shorter than any of the succeeding ones; it is slightly less than two-thirds as long as the succeed-
ing arthromere; it bears in front a well-marked, small, triangular rostrum, which is acute at the
tip, and is about two-thirds as long as the segment itself; the edge of the rostrum is considerably
raised, especially at the base. The front edge of the segment on each side of the rostrum is also
margined with an elevated ridge. The surface of the segment is rather full and convex on each
side, but not so decidedly so as the second segment. The second arthromere is about as long as
those succeeding, though not quite so long as the sixth arthromere; on each side is a low boss-like
swelling, situated obliquely, and prolonged in an oblique direction to the anterior outer edge.
The second segment is distinctly separated by an impressed line from the first, but there is not a
true articulation between them, so that the first and second cephalic segments may be said to be
consolidated and to represent the carapace of the Schizopoda. The three succeeding segments
have a transverse, uninterrupted, smooth ridge situated in the middle on the third, but in the fifth
segment near the hind margin. The sixth and succeeding segments are smooth and even. The
body is of even width to near the telson. The lower edges of the segments are evenly rounded,
those of the hinder abdominal segments are more acutely rounded.

We have been unable to detect any positive traces of the eyes, nor can we state whether they
were sessile or stalked, though if they were present and sessile we do not see why they should not
have been preserved in some of the specimens (particularly 501° and 406°),"

The first pair of antennze seem to arise directly from each side of the small, short, rudimentary
rostrum. The scape is three-jointed, and not very long and slender; second joint not so thick,
and about one-fourth shorter than the first and twice as long as thick ; third joint long and slender,
considerably longer than the second. The scape bears two flagella, which are long, slender, mul-
tiarticulate branches of unequal length, of which the inner is the thicker and shorter, the outer
flagellum much slenderer and longer, the entire length of the antennie being one-half that of the
second or outer pair. The second pair of antennae have also a three-jointed scape (which is not
accurately represented in Meek and Wortheu’s figure). The basal joint is short; second joint shorter
than the first, with two unequal internal spines; third joint slightly longer than the second and
much smaller; there are traces of a small antennal scale; the flagellum is long and slender, its
entire length about half that of the body.

There are twelve pairs of feet (506*,°), a pair to each segment situated between the head and
penultimate uromere or abdominal segment; these, with the caudal pair of appendages, make in all
thirteen pairs of legs. .

The number of arthromeres or body-segments is sixteen, counting the head as consisting of two
when seen-from above, and the telson as a rudimentary arthromere, so that there are thirteen
arthromeres between the head and telson, each of them bearing legs. There is no apparent dis-
tinction, as regards the segments themselves, into cephalothorax and abdomen (urosome), but there
are two cephalic, nine thoracic segments, and seven abdominal, counting the telson as the seventh.
The first seven pairs of (thoracic) legs are much alike in appearance, reminding us of those of Peta-
lophthalinus and Gnathophausia; these are succeeded by five pairs of abdominal appendages, which
are about half as long and large as the thoracic legs. The first pair of thoracic legs (which do not
seem to be mandibular palpi) are considerably larger (broader and longer) than the succeeding
ones. It is composed of six joints; the first and second rather narrow; the third broad, with, ac-
cording to Meek and Worthen, “ three” spines on the “ under side” (these were not to be seen in
my specimens, though undoubtedly existing there ); fourth longer than the third, with three spines;

‘Before going to press I received from Mr, Lacoea very large specimen, his No. x4, in which are two large smooth
concavities, one on each side of the base of the head; it is possible that these are sessile eyes.

ON THE SYNCARIDA. 125

fifth joint thicker than the fourth, thickening towards the distal end, with four spines, the fourth
spine the largest and as long as the joint is thick ; the sixth about two-thirds as thick as the fifth,
with two remote spines on the under side and ending in two spines, one of them very large and
stout (there is possibly a third small spine). In Meek and Worthen’s figures the spines are errone-
ously drawn on the outer side of four joints; we find that the spines are situated only on the two
penultimate joints; the terminal claw is not represented by Meek and Worthen. The succeeding
Six pairs are all about the same size and length, being large, well developed, long, and slender,
about one-half to two-thirds as thick as the first pair (406°), with no traces of a gill; the second
pair are a little stouter than the others and apparently spined on the penultimate joint; the sev-
enth pair the slenderest and nearly as long as the first pair; the three basal joints are long and
slender, the third very distinct, long, and slender; fourth joint long, slightly swollen in the mid-
dle; fifth equal to the sixth in length, but slender, slightly thickened towards the distal end; the
sixth somewhat longer than the fifth, ending in a point; none of the terminal joints appear to be
chelate.

The abdominal appendages are distinetly biramous and schizopodal in their appearance. Each
apparently consists of a small, narrow, jointed limb and a larger exopodital branch (or gill| ; see
406%»), We can see traces of the first two pairs. In another specimen (501%) the first three pairs
of abdominal legs are to be plainly seen; the exopodital or respiratory and swimming ramus is
sessile, lanceolate-oval, and broad, thickened on the hinder (?) edge. In Mr. Carr’s specimen No.
1 are distinct traces of a biramous append ige on the fourteenth and fifteenth (penultimate) seg-
ments; and in his No.3 there are to be seen the traces of the second—fourth pairs of abdominal feet
with doubts rami, the hinder ramus the smaller and narrower. In an abdominal foot (in Lacoe’s
No. 406) the second joint is narrow, lanceolate-oval, rounded at the tip, from which arise a series
of long slender sete, about twelve in number, which form an oar-like appendage equaling in size
the basal joint; total length of the limb 14.5" (the basal joint 8"™, the row of sete 6.5"™"=14,5™™),
These legs remind us somewhat of those of Squilla, as do the first thoracie pair, from their being
larger than the others and armed on the under side with stout spines.

The telson is very long and slender, narrow, acute, the end very slender, with long sete on
each end; it is a little longer than the caudal feet (aropoda) on each side of it. The caudal feet,
or sixth pair of uropoda, are divided into two long, large, acute rami (endopodite and exopodite)
arising from a small, short basal joint (Carr’s No. 1). The two rami are of nearly the same size
and length, both edges of each branch being setose (the sete are not so numerous and close as
represented in Meek and Wortheu’s figure).

Of forty specimens examined, the total length of the largest example, including the eaudal
appendages, but not including the antennwe, was 75™™ (Lacoe’s No. 55"); another still larger
(No. y*) was 85™™ in length; a specimen received from Mr. Carr was 55™™ in length.

In a specimen of A. event, 45™ in length, 1 made the following measurements: Width of
the body, 6-7" (in Lacoe’s 501”: Width of first cephalic segment, 5.5°"; of second segment, 6";
length of first and second head-segments together, 6""; length of rostrum, L""; length of sixth seg-
ment, 3.5"") ; length of first antennw, about 12"; ie igth of second antenne, 26°"; length of first pair
of feet, 20°"; greatest width of fifth joint of first feet, 2°"; length of abdominal feet, 18-19"; length
of telson, 13"°; length of caudal appendages, 12"",

Many of the specimens are preserved flattened out, showing the back, with the legs spread
out symmetrically on each side; others are preserved lying on their side, with the body somewhat
arched, and then they present a shrimp-lke appearance, though on a superficial examination
reminding one of an Amphipod lying on its side,

The foregoing remarks apply to the larger specimens described by Meek and Worthen as
Acanthotelson event. I cannot with certainty point out any distinctions from A. stimpsoni M.& W.,
the first-described species; the smaller specimens, which might be referred to the latter species,
are evidently the young of A. event M. and W. Hence the specific name should be Stimpsoni.

The characters of this Crustacean are such as to forbid our referring it to any known group ;

we therefore suggest that it forms the type of a suborder of thoracostracous Crustacea, which we

would designate as the Syncarida.
What we should regard as the differential characters of the group Synearida, to which Acantho-

126 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

telson belongs, are the sixteen free segments of the body, which are homonomous or of uniform
size, the first and second, however, being soldered together; the absence of a true carapace; the
seven pairs of schizopod-like legs, the first pair spined and raptorial, slightly reminding one of
those of Squilla; the second pair also spined; the antenn of both pairs are long and slender, the
two flagella of the first pair being very unlike any sessile-eyed or edriophthalmatous Crustacean ;
the six pairs of abdominal feet, which are long, slender, and with a general resemblance to those
of the Schizopoda; the broader, oar-like swimming ramus, ending in long sete. Any doubts as to
the macrouran affinities of the Synearida are removed by an examination of the long, acute telson
and last pair of abdominal appendages; the Sarin are biramous, the divisions flattened from
above downwards, so that they with the telson serve, as in schizopods and shrimps, for propelling
the body backwards when the animal is disturbed.

We should regard the Synearida as the lowest group or suborder of Thoracostraca, but much
nearer the Schizopoda than the Cumacea; they form a connecting link between the Amphipoda and
Thoracostraea, but at the same time in Gietr most essential characters stand much nearer to the Schi-
zopoda than the Amphipoda; the lack of a carapace, even a rudimentary one, and the homonomous
segmentation, causing them to bear a resemblance to the Edriophthalma, which they would not
otherwise present. The Syncarida may be regarded as the homotoxial equivalents of the Decapoda,
Schizopoda, or Stomapoda. To the Isopoda, Acanthotelson presents superficial resemblance, due
to the slightly vertically compressed body and the homonomous segmentation. The Edriophthalma
(Arthrostraca of some late authors) are defined by Claus as “ Malacostraca with lateral sessile
eyes, usually with seven, more rarely with six or fewer separate thoracic segments, and the same
number of pairs of legs, without a carapace,” but this definition does not express those differences
in the form of the antenne, the thoracic legs, and abdominal appendages, especially those of the
end of the urosome or abdomen, which are characteristic of the sessile-eyed Crustacea as distin-
guished from the Thoracostraca.

From the Isopoda, in which the body is usually broad and vertically flattened, with seven free
thoracic segments, while the abdominal legs are lamellar and closely appressed to the short abdo-
men, our Acanthoteson plainly differs in the long bi-flagellate Decapod-like first antenn, in the
long homonomous segments of the abdomen, and the schizopodal abdominal feet, and especially the
Schizopod-like telson and last pair of feet, adapted, as in the shrimps, for striking the water from
above downwards.

The Amphipoda are, in general, characterized by their laterally compressed body, with lamel-
late gills on the thoracic feet, and an elongated abdomen, of which the three anterior segments
bear the swimming feet, while the three posterior bear posteriorly-directed feet, adapted for
springing (Claus). Now, if Acanthotelson is not an Lsopod, still less should it be regarded as
related to the Amphipoda. The first antenne are entirely unlike those of any known Amphipods,
the latter having a very short accessory flagellum; the second antennwe of Acanthotelson are
strictly decapodous in appearance and very different from those of the Amphipoda, whereas in
Gammarus the scape is as long as the flabellum. Although there are seven free thoracic segments
in Acanthotelson as well as in Gammarus and other Aimphipoda, those of Acanthotelson are not
compressed any more than in the Schizopoda, and there are no traces of epimera; on the contrary,
the free edges of the thoracic and abdominal segments are much as in the Schizopoda and Caridea.
The thoracic appendages of Acanthotelson are, on the whole, like those of the Stomapoda and
Schizopoda. We cannot detect any traces of mouth-parts, mandibles with their palpus, or maxilla;
but the thoracic legs do not present any close resemblance to those of the Amphipoda, the first
pair being as much, if not more, like those of Squilla than any Amphipod with which we are
acquainted, while the three posterior pairs, which are in form and size like those in front, entirely
differ from those of Gammarus and most other normal Amphipods, in which the basal joint is very
large and triangular. Turning to the abdomen, the difference in that of Acanthotelson from that
of the Amphipods is still more marked. The first five pairs of uropoda, or abdominal appendages,
are, in Acanthotelson, all formed apparently on the same plan, not essentially different from those
of Schizopods, while the last pair are flat and on the same plone as the telson and intimately asso-
ciated with the latter; in short, these parts are formed on a truly macrurous plan and most approach
those of the Schizopods, in which the telson and rami of the last pair of feet are narrow and more

ON THE SYNCARIDA. 127

or less acute at the end. There is nothing in the structure of the urosome and its uropoda in
Acanthotelson to remind us of the same parts in the Amphipoda.

Excluded from the sessile-eyed Crustacea, and foreed to place Acanthotelson in the Thoraéos-
traca, we are confronted by the lack of a carapace and the homonomous segmentation of the body.
These are essential fundamental characters, but still the nature of the appendages and telson is
such as to forbid us from rejecting the Synearida from the ordinal limits of the Thoracostraca.
We are compelled, therefore, to regard the group as a suborder standing near or at the base of the
Thoracostraca, not far from the Stomapoda and Schizopoda, and with appendages closely homol-
ogous with those of these two groups. The Synearida, from their lack of a carapace, and from the
well-formed dorsal arch of the seven thoracie segments, we are obliged to consider as an annectant
or synthetic group, pointing to the existence of some extinet group which may have still more
closely connected the sessile-eyed and stalked-eyed Crustacea.

NOviIcE OF ACANTHOTELSON ? MAGISTER (n. sp.).
Pl. Il, Figs. 4,5.

I have received from Mr. J. C. Carr, for examination, a specimen from Mazon Creek, collected
at the same place as the nodules containing the Acanthotelson, showing the remains of a crustacean
closely similar to, if not generically identical with Acanthotelson. Unfortunately the head and anten-
ne are not preserved sufficiently well for description, so that the following account should be regarded
as provisional, until better-preserved specimens are found. As seen by the photograph (PI. I, figs.
4,5), the animal was of the same general shape as in Acanthotelson; when it died the body was
curved on itself, so that the two longer antenne crossed the end of the abdomen with its append-
ages. The abdomen in its dorsal aspect, with the telson and last pair of uropoda, are tolerably
well preserved. The faint traces of the head, unless we are mistaken, show that it was of the
same general shape as in Acanthotelson, There are traces of two pairs of antenniwe; one fragment,
the innermost, showing traces of six joints; and there are faint impressions, not showing the joints,
of two long autenne, which are about half as long as the body. There are no traces of any thoracic
or abdominal appendages except the last pair of uropoda.

Description.—Body very broad, being nearly twice as broad as the largest Acanthotelson eveni,
M.& W. The penultimate abdominal segmentis a little more than one-half as long as the terminal
segment. The last segment is very large and square, the sides nearly even, not narrowing poste-
riorly, and it is the broad square shape of this segment which will readily enable one to separate
it from the previously described species of Acanthotelson. The telson is stout, broad at the base,
and rather short, much shorter than the uropoda appended to the same segment. The terminal
uropoda are broad and stout, with no traces of set. The basal joint is broad, triangular, but a
little longer than broad; the outer ramus is of moderate length, ensiform, and slightly longer than
the telson; there is only a fragment of the inner telson left in the fossil, which, however, shows
that it was considerably narrower and smaller than the outer pair.

Probable length of the whole body, not including the antenni or telson, 70",

Length of penultimate abdominal segment, 5™™,

Breadth of penultimate abdominal segment, 12™™,

Length of terminal abdominal segment, 10™™,

Breadth of terminal abdominal segment, 11™™,

Length of telson, 10™™; breadth at base, 2™™,

Length of basal joint of last pair of uropoda,4™™; breadth, 3.5™™,

Length of outer ramus of last uropod, 11™™; breadth, 2",

Explanation of Plate I.

Fig. 1. Acanthotelson stimpsoni M. & W., restored, enlarged twice.

Fig. la. Acanthotelson stimpsoni M. & W., head and antennx seen from above, enlarged twice.
Fig. 1b. Acanthotelson stimpsoni M. & W., first thoracic leg x %. ‘

Fig. le. Acanthotelson stimpsoni M. & W., sixth thoracic leg x#.

Fig. 1d. Acanthotelson stimpsoni M. & W., telson and last pair of uropoda x #.

Fig. 2. Acanthotelson ? magister Pack., x}. All the figures drawn by Dr. J. S. Kingsley,

128 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES.

Explanation of Plate Il.

Fig. 1. Acanthotelson stimpsoni M. & W. :
Fig. 2. Acanthotelson stimpsoni M. & W., reverse of fig. L.
Fig. 3. Acanthotelson stimpsoni M. & W.

Fig. 4. Acanthotelson ? mggister Pack.

Vig. 5. Acanthotelson ? magister Pack., reverse of fig. 4.

From photographs taken by Mr. Robert L. P. Mason.

Note on an additional specimen.—Since this memoir was sent to the printer I have received a larger specimen from
Mr. Lacoe, labelled ‘* Braidwood, Ill, Q'”, which, exclusive of the antenne and telson, measures about 82", There
are traces of four pairs of thoracic feet which are long and slender and bent backwards from the head, reminding us
of the four hinder legs of an ordinary shrimp seen from one side. There are traces of the antenna, better preserved
than in the original specimen. There appear to be a pair of large antenni, the scape composed of three large joints,
the second and third smaller and together equalling in length the basal joint; these antenne appear each to bear a
large antennal scale, resembling those of the Macrura, and reaching as far as the middle of the third antennal joint.
The characters shown by this specimen lead me to refer if to a genus distinet from Acanthotelson, for which the
the name Belotelson (the entire name, Belotelson magister) is proposed, Additional] specimens are much desired to
complete our knowledge of its affinities.

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