LAMELLIBRANCHIATA. 599 
Ctenodonta filistriata ] 
C. fecunda type as well, but this, unless we agree that the short side in those shells 
is really the posterior, does not bring them much nearer to the C. albertina type, 
since the adductors are reversed, the acuminate-ovate scar being anterior in the 
latter and posterior in the former. 
Formation and locality—A common species in the upper beds of the Cincinnati group at Clarksville 
and other Jocalities in Ohio. I am not entirely satisfied that the species occurs in Minnesota, but there 
are good reasons to believe that it may be found in the Hudson River strata near Spring Valley. 
CTENODONTA FILISTRIATA, ”. Sp. 
Fig. 44. a, right side of a cast of the interior of Ctenodonta filistriata, n. sp.: b and ¢, cardinal 
and lateral views of left valve of same; d, small portion of surface of same, highly magnified; e, hinge 
of a right valve of same, x 2; specimens from lower beds of the Cincinnati group at Covington, Kentucky: 
f and g, cardinal and lateral views of a large right valve of Ctenodonta gibberula Salter, from the lower 
Trenton near Murfreesboro, Tennessee. 
over 
Tellinomya levata HALL and WHITFIELD, 1875. Pal. Ohio, vol. ii, p. 82. (Not Nucula levata Hay, 
1847, Pal. N. Y., vol. 1, p. 150.) 
This species may be distinguished at once from C. albertina, with which it agrees 
more closely than any other known, by the delicate, crowded, thread-like concentric 
lines which cover the entire surface. Twelve to twenty of these lines may be counted 
in a space 1 mm. wide. The shape and general appearance of the shell is very simi- 
lar in the two shells, but the basal margin in the present form is always uniformly 
rounded, while the antero-dorsal angle is a trifle blunter. The latter fact is due to 
the greater bend in the hinge. The pit beneath the beak is scarcely so distinct as 
in that species, and as the hinge is a little shorter the number of denticles is less 
than the average number for C. albertina, there being usually twelve anterior and 
fifteen posterior. Finally, in perfect casts of the interior the beaks are not so much 
compressed and the ridges running posteriorly from them less sharp. 
This species is generally identified with Hall’s Nucula or Tellinomya levata, origin- 
ally described from the Trenton limestone of New York, and closely related to C. 
nitida of this report. The error of this identification is so palpable that it is really 
not worth the while to refute it. Any one at all capable of distinguishing species 
must, now that attention has been directed to the matter, see at once that the two 
shells are very different. 
Formation and locality.—In the lower beds of the Cincinnati group at numerous localities in and 
near the city of Cincinnati. A single specimen was collected by Mr. Charles Schuchert in equivalent 
beds at Granger, Minnesota. 
Mus, Reg. No. 8378. 
