, LAMELLlfeRANCHIATA. 599 



Otenodonta fllistriata ] 



C. fecunda type as well, but ^lis,- 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 localities 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, n. sp. 



Fig. 44. a, right side of a cast of the interior of Ctenodonta filistriata, n. sp.; b and c, cardinal 

 and lateral views of left valve of sam^; 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; 

 / and g, cardinal and lateral views of a large right valve of Ctenodonta gibberula Salter, from the lower 

 Trenton near Murfreesboro, Tennessee. 



Tellinomya levata Hall and Whitfield, 1875. Pal. Ohio, vol. ii, p. 82. (Not Nucula lev'ata Hall, 



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 perfeqt 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 w^ile 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 diflferent. 



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. Beg. No. 8378. 



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