PSEUDOCYTHERE. CYTHERURA. 43 



2. PsEUDOCYTHBRE Beistovii, s]p. nov. Woodcut, Fig. 5. 



Fig. 5. — Pseudocyfhere Bristovii, sp. nov. a. Eight valve (slightly broken along the ventral edge). 



h. Edge view. Magnified 20 diam. 



Elongate, convex, especially at the front moiety, subrhomboidal ; rather 

 obliquely rounded in front, arched on the dorsal and straight on the ventral 

 margin, between its anterior and posterior curves. The hinder extremity of the 

 valve is suddenly narrowed to a subtriangular and flat point, which has a convex 

 outline on its ventral, and is neatly incurved on its dorsal edge, much like the end 

 of a Bairdia. The surface bears numerous delicate, longitudinal, sinuous, raised 

 lines, which are somewhat interrupted and overlap in the mid-dorsal region, and 

 branch into fine plumose groups here and there on the anterior part of the valve. 



This elegant form is rare in the Bembridge Limestone of a brickyard south-east 

 of West-Cowes Cemetery. It is named after H. W. Bristow, Esq., F.R.S., who 

 has always taken great interest in the geology of the Isle of Wight. 



This species is allied to, but differs in detail from, Pseudocijthere Fuegiensis, 

 G. S. Brady (' Report Challenger, &c.,' 1880, p. 145, pi. i, figs. 7 a—d). 



The same piece of Bembridge Limestone yielded a few fragments of a form 

 similar or allied to the foregoing, but ornamented with still more delicate and 

 silky strife, which, under a high power, are seen to be interrupted, or elegantly 

 punctated, along their length. 



XVIII. CYTHERURA, G. 0. Sars, 1865. 



Brady, Crosskey & Eobertson, Monogr. Post-Tert. Entom., 1874, p. 191. 



1. Cytherura Pbestwichiana, Jones 8f Sherborn. Plate I, figs. 20 a, b. 



Cttheetjea Pbestwichiana, Jones ^ Sherborn. Geol. Mag., 1887, p. 456. 



This belongs to the same type as Cytherura nigrescens, B., C, and R., ' Post- 

 Tert. Entom.,' p. 192, pi. xi, figs. 28—32, but differs in its greater compression 



