On Lingidasma^ Etc. — Ulrich. 23 
nati, Ohio. The specimen figured belongs to the collection of 
Mr. Charles Schuchert. The figure represents the reticulation 
finer than is on the specimen. 
TREMATIS UMBONATA, n sp. 
Figs. 8-8 c. \ 
Dorsal valve ovate acuminate, rather strongly convex, es- 
pecially in the umbonal region, with the beak incurved and 
more or less acutely rounded. The length and breadth as 
well as the acuteness of the beak varies in different individuals. 
The extremes so far noticed are represented in the two speci- 
mens figured. Surface with fine and rather obscure concen- 
tric lines, and radiating series of minute punctures along the 
margins and on the umbonal slopes. The punctures are 
closely arranged and, as usual, increase slightly in size out- 
ward. They do not occur on all portions of the surface, being 
absent over a considerable part of the central region. Ven- 
tral valve concave, marked with fine concentric strife and a 
number of crowded rows of very minute punctures on each 
side of the foramen notch. Foramen notch small and narrow, 
situated at the bottom of an abruptly impressed U-shaped 
area. 
Two specimens have the following dimensions : (1), length, 
16.8 mm.; width, 12.1 mm; convexity, 4.0 mm. (2), length 
12.5 mm ; Avidth, 9.7 mm. ; convexity, 3.8 mm. 
The strongly elevated umbonal region of the dorsal valve, 
the concave ventral, and the elongate form, suffice to dis- 
tinguish this species from T. punctostriata Hall. In all these 
respects T. icmbonata simulates T. huronensis Billings, from 
the Black River limestone of Canada, but the surface orna- 
mentation of that species as figured by Billings (Paselozoic 
Fossils vol. I, p. 52.) is quite different. 
Formation and locality: Middle beds of the Cincinnati 
group on the hills west of Covington, Ky., and at the hill 
quarries of Cincinnati, Ohio. It is not by any means a com- 
mon fossil. The types are from the collection of Mr. C. 
Schuchert. 
TREMATIS OBLATA, n. sp. 
Fig. 9, 9 a, and 9 b. 
Trematis punctostriata Hall and Whitfield, Pal. Ohio, vol. ii, pi. i, 
fig. 8; 1875. 
Compare Trematis punctostriata Hall, 23rd Regent's Kept., p. 243> 
pi. 13, figs. 17 and 18; 1873. 
