422 
Cope. ] oe [March 1, 
There is no second ridge on the outer (trochlear) side of it. The same 
condyle terminates abruptly posteriorly on the superior face of the shaft.. 
Width of condyles in No. 1, eleven lines ; in No. 2, thirteen lines ; verti- 
cal diameter, inner condyle, eleven lines (No. 1); transverse diameter 
shaft above, eight lines. 
The proximal articular surfaces of the proximal wing phalanges are 
deeply concave, the inner protected by an elevated margin behind ; that 
of the outer, much lower. They are separated chiefly by a deep emargin- 
ation, but on their short adjacent portions by a low ridge. The process 
for ligamentous insertion is well developed. The distal extremity is 
slightly widened, and its articular surface is wedge shaped with very con- 
vex base. Its surface is slightly concave in both directions and without 
median ridge. The margin of the shaft terminates in a short tuberosity 
bearing articular surface. Transverse diameter, sixteen lines. Length 
of shaft preserved, but incomplete, nine inches, one line. 
This species is about the size of the Pterodactyle found by Professor 
Marsh in the same region,* and probably belongs to the same genus, and 
possibly to the same species. This, however, cannot be definitely ascer- 
tained as his species is imperfectly described, all the characters adduced 
except the measurement being generic. The name given by Professor 
Marsh has also been previously used, both in this genus and in Pterodac- 
tylus, and must therefore be given up. 
Remains of the two Ornithochiri above described are not rare in the 
yellow chalk of the Niobrara Group, and those obtained were mostly from 
different parts of the course of the blufts of Butte Creek. 
A DESCRIPTION OF THE GENUS PROTOSTEGA, A FORM OF 
EXTINCT TESTUDINATA. 
By Epwarp D.‘Corkg. 
(Read before the American Philosophical Society, March 1st, 1872.) 
The present article introduces to the system a new form of Testu- 
dinata of a character not heretofore found in a fossil condition. Its af- 
finities will be more fully discussed at the end of the description, but they 
appear to belong to the Sphargidide. This family is represented, in 
our present knowledge, by but one genus and one species of the recent 
seas. It is one of the most generalized, or in special characters, the most 
aberrant of the order of the tortoises, and the discovery of an extinct ally, 
even as far down in the series as the cretaceous period, is not surprising. 
The remains preserved belong to a single individual, and include many 
portions of the cranium, five vertebree more or less incomplete, the scap- 
wlar arches of both sides with the coracoid bones ; both humeri perfect, 
with nine phalanges, ten ribs, one vertebral (2), and ten marginal bones ; 
parts or wholes of four large lateral (?) dermal bones, with five distinct 
*See Am. Jour. Sci. Arts, June, 1871. 
