Orthothctes Minutus, N. Sp. — Cuininings. 149 
quadrate rather than semi-circular outline of the shell. The fig"- 
ures of Schlotheim's species also show a strongly quadrilobate 
cardinal process, while in the present species the notch is very 
shallow and the grooves are very faint. The species to some 
extent resemble O. lens from which it differs in the form of the 
cardinal process and the greater proportionate length of the 
latter species. 
Developaient. In the search for specimens of this rather 
rare species (about fifty specimens were found among several 
thousand of the commoner Spergen hill forms) a number of 
very young stages were obtained. While even the adult in- 
dividuals share in the general stunting so characteristic of the 
entire Spergen hill fauna no complete specimen in the writer's 
collection having a length of more than 5 mm., nevertheless 
these larger individuals present the usual features of maturity. 
The smallest individual observed has a length of 0.6 mm. 
and a breadth of 0.9 mm. In this specimen the ventral valve is 
roughly conical in shape, though slightly more convex toward 
the beak which projects conspicuously beyond the hinge-line 
and is very prominent. The surface shows eighteen plications 
at the margin as against forty in the largest individual ob- 
served, while the posterior, third of the shell is without orna- 
mentation except a few obscure concentric markings. The 
area is high and the large deltidium less sharply marked off 
from it than in the older individuals. The breadth at the hinge 
is conspicuously less than farther forward. 
The dorsal valve has its greatest convexity at the center and 
is also smooth for a considerable distance from the beak. It 
shows no sign of an area. 
Individuals of the length of 2 mm. have the area perpendic- 
ular to the plane of separation of the valves, and the ventral 
valve showing a slight convexity toward the front. The num- 
ber of plications has increased from eighteen to twenty-two or 
twenty-three, and the region of greatest convexity in the dorsal 
valve has approached somewhat the beak. The youngest in- 
dividual shows a marked conformity to the generalized tvpe 
of brachiopod, as was found by Beecher and Clarke to be the 
case in the species of the Waldron fauna. -■= 
* Memoirs of the Xe^v York State Museum, vol. i.. No. 1. 
