116 PROCEEDINGS OF THE ACADEMY OF 



resembles C. setigera, Hall, and C. nana, but differs from the former in 

 having oblique instead of erect spines, and from the latter in the smaller area 

 of the ventral valve. C. setigera occurs in the Hamilton and Chemung of 

 New York, and I have identified it in the blue argillaceous shales of the Huron 

 group of Michigan. C nana is found in the corniferous limestone ; and Euro- 

 pean geologists regard it as a Devonian species. 



Ciionetes Illinoisensis, Worthen, (Trans. St. Louis Acad. Nat. Sci. i. 571) ; 

 C. Logani, Hall, (Iowa Rep. p. 598, pi. xii. fig. la e and 2) ; not C. Logani, 

 ' Norwood and Pratten, (Jour. Acad. Nat. Sci. Phil. [2] iii. 30, pi. ii. fig 12, 

 a, b, c] ; C. Illinoisensis, Winchell, (Proc. Acad. Nat. Sci. Phil., Jan., 1863, 

 p. 5). This wide spread species occurs at the Grindstone quarries at Pt. aux 

 Barques, Mich. The specimens are smaller than the typical ones from Bur- 

 lington, Iowa, and perhaps for this reason do not number as many striae 

 around the margin ; but specimens from Burlington of the same age cannot 

 be distinguished. 



Collected also by A. Winchell at Rockford, Indiana. It also occurs in the 

 base of the Burlington limestone at Burlington, Iowa, (" White Collection") 

 and in the fine grained sandstones of Licking County, Ohio. 



This species may be confounded with C. Shumardianq, De Koninck ; but 

 the latter has 270 to 280 or more radiating striae, which are less distinctly 

 isolated from each other. The former has from 100 to 125 striae. 



Cheilitis geniculates, White, (Proc. Bos. Soc. Nat. Hist. ix. 29). A single 

 ventral valve, collected by A. Winchell at Rockford, Indiana, cannot be dis- 

 tinguished from this species. 



Choketes Logani, Norwood and Pratten. In a former paper I pointed out 

 the error of Hall's identification of C. Logani, N. & P., though this species 

 had not at that time fallen under my observation, and, I believe, has been 

 seldom seen since first described. I have now, however, in some later addi- 

 tions to the " White Collection " of the University, a number of examples of 

 C. Logani, N. & P., fully answering to the original description and figure. 

 These specimens are from the base of the Burlington limestone, and the ma- 

 trix holds C. Illinoisensis in the same association, as previously believed. 



C. Logani, N. & P., as far as I have observed, is restricted to the horizon 

 of the Marshall or Burlington sandstone including the base of the Burlington 

 limestone, which belongs evidently to the same epoch. Prof. Hall, however, 

 has a small Ciionetes from the Tully limestone, which, he informs me, he has 

 decided to refer to C. Logani, (see 11th volume Paleontology of N. Y.), a 

 reference to which, with full acknowledgement of his superior authority, I 

 cannot, at present, give my assent. The Tully limestone species presents a 

 series of concentric rugosities or wrinkles, which extend both across the ribs 

 and the intervals between the ribs ; while in C. Logani the rugosities are 

 feebler, and are confined to the crests of the ribs. 



C. Logani is also recognized in Ohio, with about 40 to 50 ribs. It hence 

 appears that the species, like C. Illinoisensis, Worthen, and C. multicosta, 

 WiDchell, ranges from the Burliugton limestone into the sandstone below. 



I may perhaps be permitted to add that some typical specimens of C. Logani 

 in Prof. Hall's cabinet, sent to him by Dr. Norwood, are imbedded in a matrix 

 .if oolitic limestone, such as occurs at the base of the Burlington limestone. 



Ortiiis Michelini, L'Eveille, occurs in Whittlesey's collection from "Wa- 

 verly sandstone, near Newark, Licking County, Ohio." Another Ortiiis from 

 Akron, Ohio, resembles the Burlington species commonly referred to O. Va- 

 nuxemi (?), but differs in the parallel direction of the dental lamellae, and in 

 the very indistinct character of the radial striation. 



Still another Orthis, received from Dr. Shumard and collected at Sulphur 

 Springs, St. Louis County, Missouri, is perhaps the species referred by the 



[July, 



