1893.] Structure of Carapace in Rhinocaris. 793 
ON THE STRUCTURE OF THE CARAPACE IN THE 
DEVONIAN CRUSTACEAN RHINOCARIS; AND 
THE RELATION OF THE GENUS TO 
MESOTHYRA AND THE 
PHYLLOCARIDA. 
By Joun M. CLARKE. 
In the original account of the peculiar fossil Rhinocaris; the 
carapace was described, from the best evidence then obtainable, 
as univalvular, with a rostrum projecting conspicuously and 
consolidated with the valve. The type of structure appeared 
to be a remarkable departure from that exemplified in the pre- 
vailing phyllocarid crustacea of the Devonian (Echinocaris, 
Llymocaris, Tropidocaris), and seemed to evince in the very 
structure mentioned, strong affinities with the Decapods. 
The diagnosis of the genus was virtually based upon a 
single specimen in which the carapace had been laterally com- 
pressed in such a manner as to demonstrate the non-existence 
of a median suture or hinge, and to conceal any evidence of 
other longitudinal sutures; and in which, also, the rostrum 
was laterally flattened and apparently continuous with the 
carapace. 
For several years I have been carefully searching for addi- 
tional information concerning this peculiar crustacean. A 
considerable number of specimens from the shales of the 
Hamilton group of Ontario County, New York, have come into 
my hands, but the test of the animal is so very tenuous that 
it seems well nigh impossible to secure examples which have 
not been subjected to some distortion, and that is usually the 
greatest at structural points of critical importance. Several 
excellent specimens, however, have been obtained, some of 
them kindly furnished by Mr. F. B. Loomis, of Spencerport, 
EY. 
The carapace of Rhinocaris columbina Clarke, (the typical 
1 Paleontology of New York, vol. vii, pp. lviii, 195, pl. xxxi, figs. 16-21, 1888. 
