﻿LEPTyENA. 



85 



Length 11^, width 18 lines. 



Obs. As we cannot offer a complete or even satisfactory description of this shell, which 

 occurs in the state of imperfect casts or impressions in brown grits at Looe in Cornwall, it 

 will be preferable for the present not to give it a specific denomination. 



Lepivena interstrialis, Phil. PL XVIII, figs. 15 — 18. 



Okthis interstrialis, Phillips. Pal. Foss. of Cornwall, Devon, and West Somerset, 



p. 01, pi. xxv, fig. 103, 1841. 

 Lept.ena — Schnur, in Dunker und v. Meyer's Palseontographica, vol. iii, p. 



222, pi. xli, fig. 2, 1853. 



Spec. Char. Transversely semicircular, concavo-convex, wider than long ; cardinal edge 

 and hinge-line equal to the width of the shell, extremities angular and slightly projecting ; 

 ventral valve uniformly convex ; dorsal valve concave, following the curves of the opposite 

 one ; ventral area rather narrow, but wider in the middle under the extremity of the beak, 

 and divided by a small pseudo-deltidium ; dorsal area linear, and of almost equal width along 

 its entire length ; surfaces of both valves ornamented by from twelve to twenty or more 

 simple striae of about equal thickness throughout, which originating at the beak extend to 

 the margin, and leaving a wide interspace between them. In the centre of these inter- 

 spaces and at about the middle of the shell a smaller rib is observable, and which extends 

 to the margin, while the whole surface of each interspace is marked by five, seven, or 

 eight fine, longitudinal, thread-like strise. Proportions variable. 

 Length 11, width 15 lines. 



Obs. This shell is very variable in the degree of convexity of its ventral valve ; the 

 ears, or cardinal angles, are also more or less produced, and the striation is slightly variable 

 in different examples, but still always assuming the same character. In some specimens, 

 as in fig. 17, there exists, to a certain distance from the beak, slightly marked concentric 

 wrinkles in the interspaces. 



Prof. Phillips observes, that in general appearance Lept. interstrialis resembles L. 

 sericea or L. transversalis, but that it is distinct from both. 



L. interstrialis occurs in the Middle Devonian Limestone of Woolborough quarry, 

 near Newton Abbot ; Bradley ; Barton and Lummaton, near Torquay ; Dartington and 

 Black Hall, near Totness ; Plymouth, &c. 



On the Continent it occurs at Gerolstein, in the Eifel. 



