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 Leptcena decipiens, 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. Billings 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 Leptcena Llandeilo- 
ensis, f from the Upper Llandeilo of Ayrshire, and it may also be included in 
this genus. 
The name Lept^enulopsis 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 Leptcenulopsis 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. 
* Palaeozoic Fossils, vol. i, p. 73, fig. 67 c. 
f See Supplement to British Silurian Brachiopoda, p. 171, pi. xii, figs. 26-29. 1883. 
* Die Fauna des Graptolithen-Gesteines; Ein Beitrag znr Kenntniss der silurischen Sedimentar 
Geschiebe der norddeutschen Ebene, von Karl Haupt. Band liv des Neuen Lausitzischen Magazins, 
Gorlitz, 1878, p. 31. 
t Ueber das Alter des sogen. Graptolithen-Gesteines mit besonderer Beriicksiclitigung der in denselben 
enthaltenen Graptolithen : Zeitsehrift der deutschen geologischen Gesellschaft, vol. xli, p. 695. 1890. 
