294 PALAEONTOLOGY OF NEW YORK. 



The structure of the articulating apparatus is the essential basis of distinc- 

 tion between this fossil and Plectambonites, but there is also no trace of 

 the characteristic muscular scars of the latter genus. There can be little 

 doubt that the species Leptana dedpiens, Billings, from the same formation and 

 locality, belongs to the genus Leptella. Without having had access to the 

 original specimens, the figure given by Mr. Billtngs of the interior of a brachial 

 valve,* showing the double, erect cardinal process, the strong crural plates and 

 the concave visceral area, seems sufficient to determine this point. Precisely 

 similar features are shown in Davidson's figures of his species Leptana Llandeilo- 

 ensis,\ from the Upper Llandeilo of Ayrshire, and it may also be included in 

 this genus. 



The name Lept^^inulopsis was proposed by Haupt, in 1878,| but as the work 

 in which it was described has not been accessible, no opinion can be expressed 

 in regard to its value. The term has been used by Jaekel,§ who refers to the 

 species Leptcznulopsis simplex, Haupt, certain small, smooth, semicircular, slightly 

 convex shells, of the age of the Wenlock shale. This author also observes 

 that Haupt included in this genus a few shells having the general aspect of 

 Chonetes minima, Sowerby ; but this, according to Davidson, is a strongly plicated 

 shell, though without evidence of cardinal spines. 



* Palieozoic Fossils, vol. i, p. 73, fig'. 67 c. 



t See Supplement to British Siluriiin Brachiopoda, p. 171, pi. xii, figs. 26-29. 1S83. 



♦Die Fauna des Graptolithen-Gesteines; Ein Beitrag zar Kenntniss der silurischcn Si'dimenttir 

 Geschiebe der norddeutschen Ebenc, von Karl Haupt. Baud liv des Neuen Lausitzischeu Magazins, 

 Gorlitz, 1878, p. 31. 



t U«l>ei- das Alter des sogeu. Graptolithen-Gesteines mit besonderei- Beriicksichtigung der in denselbeu 

 enthaltenen Graptolithen : Zeitsfhrift der deutschen geologischen Gesellschaft, vol. xli, p. 695, 1890. 



