246 Twenty-Third Report on the State Cabinet. 



In the mean time it may be mentioned that the genus Tremaiis 

 geems to be worthy of more than subgeneric distinction, the differences 

 between it and Discina being much more marked and important than . 

 between the fossil forms of the so-called Discina and Okbiculoidea. 



In the limestone beds accompanying the shales of the Quebec Group 

 near Troy, there is a minute discinoid phosphatic shell which I have 

 long known in its exterior character as having the concentrically stri- 

 ated and obscurely radiate surface, with an eccentric apex, like many 

 of the Discinse. The interior of the shell (dorsal valve) is distinctly 

 marked by nine radiating depressions, the central one of which extends 

 toward the margin nearest the apex, with four others upon each side. 

 At the extremities of some of these depressions there are distinct mus- 

 cular markings ; but were all these to be considered due to the muscular 

 .^, . organization we would scarcely recognize the fossil as a Brachiopod, but 

 / rather as a Gasteropod. The general character of shell, however, is 

 such as to ally it with the Discinidse, and since we do not yet know any 

 Gasteropod of similar form and character in the older rocks, I propose 

 v'^^for this fossil the name of Discinella.* 



The species which, in the Sixteenth Report on the State Cabinet, 

 / was placed by me, with doubt, under the genus Obolella of Billings, 

 was thus referred rather in deference to Mr. Billings' expressed opinion, 

 than with its correspondence to the generic description and figure of the 

 author. The grooving or emargination of the apex of both valves and 

 tlie thickening of the edges of the shell on each side below the apex, 

 together with the form and character of the muscular impressions, would 

 also separate this species from Obolella as described and figured by Mr. 

 Billings. I shall therefore indicate this form as a distinct genus under 

 the name Dicellomds. The species described by me as Orhicula? 

 crassa in vol. 1, Pal. N. Y., has a similar form of muscular impression 

 and will fall under the same genus [Plate 13, figs. 6-9]. 



In the Twentieth Beport on the State Cabinet of Natural History, 

 I published, under the name of Oholus Conradi, a form which I am far 

 from regarding as a true OBOLus.f 



*In the preceding month of February (1871,) I sent drawings of this fossil to Mr. 

 Davidson, proposing the name Discinella therefor. Mr. Davidson's long study and 

 extensive knowledge of the Brachiopoda will entitle his opinion to paramount im- 

 portance in the determination of the relations of the fossil. 



f See Twentieth Report on the State Cabinet, 1868, page 368, and revised edition, 

 1870, page 375. 



The casts of this species, with the gutta percha molds made therefrom, are the speci- 

 mens referred to by Mr. Dall as the Trimerella seen in my cabinet. * My opinion 

 regarding their relations to Trimerella is expressed in the re^iort cited, and the speci- 

 mens have not been so labeled in my collection. 



♦Dall: Revision of the Terebratulldse and Lingulida3, etc. : Amer. Jour. Conch, vol. vl, part 

 8, p. 161. 1870. 



