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MEMOIES 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 iiiipendages, but in the more important char- 

 acter of having its thoracic legs simple, and not bifid, as in the Schizopoda." 



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



We will now describe in detail Palwocaris typus, restoring it so far as possible in our description 

 from the specimens received from Messrs. Lacoe and Carr, amountiag 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 ai'e no traces of a carapace, but 

 the head is phiinly distinct 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 Palceocaris is composed of the same number 

 of segments as in the Schizopoda, but as the moiith 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 antennae 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 half as long as the lirst ; third, moder- 

 ately long, considerably longer than tiie second ; flagella nearly equal in size, long and slender. 



The second antennse 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 tirst pair are two other 

 appendages like the legs, 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, tlie three distal joints forming 

 the greater part of tlie limb. The terminal (seventh 1) joint is very long and slender, and probably 

 ends in a 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 siiorter than the third joint from the end. 



The endopodites* are distinctly 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, i. e., 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. 1 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 



* I had regarded these appendages as breeding lamellae, but Dr. Kingsley suggests that they are endopodites, aud 

 though the joints are very iudistiuct, I am disposed to accept his correction, and will speak of them as endopodites. 

 We should, on general grounds, regard them as endopodites 



