1885.] Geology and Paleontology. 791i 
existing between the thoracostracous suborders Syncarida and 
Schizopoda. 
Palæocaris was first described by Messrs. Meek and Worthen 
in the Proceedings of the Academy of Natural Sciences of Phila- 
delphia, 1865, p. 48, from specimens occurring in claystone 
nodules in the lower part of the true coal measures, at Mazon 
creek, Morris, Grundy county, Illinois. Afterwards in the third 
volume of the Report of the Geological Survey of Illinois, 1868, 
the same authors figured the fossils and expressed themselves as 
follows regarding its affinities : “ Hence it would seem to present 
something of a combination of decapod (macruran) and tetra- 
decapod characters. That is, it possesses the caudal appendages, 
anteriorly-directed thoracic legs, the antennze (some of the speci- 
mens appear also to show basal scales to the outer antennz), and 
general aspect of a macruran, 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 pedunculated 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 becomes a matter of interest to determine to 
which of the subclasses, decapods or tetradecapods, it really be- 
longs. 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. Professor Jordan and Mr. Meyer seem to have 
regarded Gampsonyx as a tetradecapod, connected with the Am- 
phipoda, but also possessing macrural decapod affinities. Profes- 
sor Dana, however, regards it as a low type of Macrura belong- 
ing to the section Schizopoda. He and Dr. Stimpson, to whom 
we sent sketches of our better specimens of Palezocaris, 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. s 
“ Generically it is separated from Gampsonyx, figures of which 
(cuts Cand 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.” | 
In our specimens we were able to detect well-marked narrow 
lanceolate oval breeding lamellz on eight pairs of appendages, 
It should be observed that the breeding lamellz 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 Mr. Meyer’s figure of Gampsonyx Jimbriatus ; in 
the latter there is also present what is apparently a large coarsely- 
spined mandibular palpus, somewhat like that in the male of the 
existing deep-sea schizopod, Petalophthalmus armatus, described 
