SHUMARD—CRETACEOUS FOSSILS. 609 
strongly marked on the superior than the inferior valve, The 
dimensions of an average specimen, are— 
Length, 1% inches; width, from beak to base, 2,35 inches; 
thickness, ,% inch. 
top of the Lower Cretaceous, near Sherman, in the bluffs of 
Post-Oak Creek, and various other localities in Grayson coun- 
ty. Itis found in connection with remains of Squalide, Os- 
trea congesta, and Corbula Graysonensis. Collected by Dr. 
G. G. Shumard. 
ECHINODERMATA. 
GENUS CIDARIS. 
C. HEMIGRANOSUS, N. Sp. — 
There are several fragments of this remarkably fine Cida- 
s 
ris in the Texas State Collection. The most perfect speci- 
gently convex, somewhat irregular, and each piece terminates 
outwardly in a small tubercle. The union of the two ranges 
is indicated by a median shallow linear groove, which is waved 
margins. The poriferous avenues are much de 
rather more than half the width of the non-poriferous space. 
The pores in a full-grown specimen are transverse 
but In yo 
impressed subcircular, or rather polygonal, and occupy fete 
than half the greatest diameter of the pieces 5 they. Pr mace 
areole the surfaces of the plates are elegantly braamontes 
m large, transversely elongated granules, and smaller 
