from the Upper Devonian Rocks of Ohio. 41 
This is, so far as I am aware, the most ancient Decapod 
crustacean yet recognized, and on that account alone is of 
great interest. The character of the caudal plates, in having 
the parts combined to form a solid plate on each side of the 
telson, is also an interesting feature, if rightly understood. 
From the impression of the plate as seen on the ventral side, 
it was at first supposed to be of a single element only, but on 
obtaining an impression in the fragment of rock, chipped from 
the top or dorsal surface, the obscure lines of the first and 
one side; the others being concealed by the rock. The 
abdominal appendages are inclined backward from their point 
of origin, ivtiie in most of the allied living forms as Atyovdes, 
Regulus, Pandalus and others, they are inclined in the opposite 
direction ; but this is not necessarily of importance. The eye- 
stalks appear to have been very short, judging from the 
spherical cavities beneath the anterior extremity of the cara- 
pace, which are small, close together and shallow. 
The earliest form of Decapod crustacean previously described, 
so far as I can ascertain, is given by Mr. Salter in the Quart. 
Jour. Geol. Soc. London, vol. xvii, p. 581, 1861, as Palwocran- 
gon socialis, said to be from the Lower Carboniferous limestone 
of Fiefshire, Scotland. There is another supposed Decapod, 
Gitocrangon, noticed by Richter (Beitrige Paleont. Thuring.), 
from the Upper Devonian, which is mentioned by Salter, but 
of which he says he is doubtful if it be a crustacean at all. 
I have not seen the work in which the original description 
occurs, and can only judge of its nature from Mr. Salter’s 
remarks, 
PaLZoOPALZMON NEWBERRYI, 0. sp. 
Body slender, the carapace forming a little more than one- 
third of the entire length, higher than wide, narrowed ante- 
riorly and truncate behind; being longer below than above; 
median line carinate, with a second carina on each side a little 
below the crest; anterior end not rostrate but obliquely trun- 
cate, and sloping rapidly backward above the truncation, form- 
ing, when looked upon in front, a narrow, elongated shield- 
shaped and slightly depressed area, obtusely pointed above 
and rapidly widening at the base, the lateral carine rising 
tom the lower angles; lower posterior angles rounded; basal 
margins gently curved throughout and bordered by a narrow, 
thread-like band with a narrow groove within it. Abdomen 
moderately robust, highly arched along the dorsal line, the 
