﻿SCABR^E. 



127 



single valves have been obtained. The internal mould is not known. Dimensions of 

 the specimen figured. — Length 16 lines ; height 13 lines ; thickness through a single 

 valve 5 lines. 



Named after Mr. C. J. A. Meyer, F.G.S., whose researches in the Cretaceous rocks of 

 the southern counties of England have contributed materially to a more exact knowledge 

 of the Greensand formations, and of their relations to similar deposits elsewhere. 



Trigonia Etheridgei, Lye, sp. nov. Plate XXVII, figs. 1, 1 a, 1 b, 2, 3, 3 a. 



Tkigonia caudata, Ibbetson and Forbes. Table showing distribution of Lower Green- 

 sand Fossils in the Isle of Wight, Bed 

 No. 3 (exclude Upper Greensand), Proc. 

 Geol.Soc, vol. iv, No. 101, p. 414, 1844. 

 — — Fitton. Stratigraphical section from Atherfield Point to Black 



Gang Chine (Beds 1, 2 ; Fossil 63). Quart. Journ. 

 Geol. Soc, vol. hi, No. 11, p. 289, 1847. 



Shell sublimate, much inflated, compressed upon the anterior face, which is very 

 wide ; umbones much elevated, erect, very large, much incurved and recurved, their 

 apices are slightly separated when the valves are close ; their recurvature is so consider- 

 able that the ligamental fissure is seen anterior to them (Plate XXVII, fig. 1 a, 1 b) ; 

 the anterior border is very short and truncated, slightly curved with the lower border, 

 which is nearly straight, and both borders are nearly of equal length ; the upper border 

 is much excavated, its posteal extremity terminating abruptly at the produced posteal 

 portion of the valve. The escutcheon is unusually large and deeply excavated, its 

 superior or inner border is slightly raised, it is traversed transversely by ten or eleven 

 narrow, widely separated, slightly serrated costellse ; the outer border is elevated and 

 rounded ; its posteal portion is rendered bipartite by a well-marked mesial furrow, 

 constituting a very narrow and distinct area; near to its caudal extremity are some 

 transverse irregular plications. The fully developed shell has upon its sides about 

 seventeen narrow, elevated, ridged costae ; they occur at regular distances and are very 

 widely separated • about nine costae originate at the anterior border and curve slightly 

 outwards to the flexure of the valve, thence they are suddenly directed obliquely 

 upwards to the area ; the four lower costeal ridges of this anteal series are more than 

 usually elevated at their middle portions or at the flexure of the valves, where they become 

 broad and projecting, each forming a kind of lobe and having two or three rounded, 

 irregular nodosities ; the succeeding more posteal costae (eight in number) are smaller, 

 acute, narrow, and high-ridged, passing perpendicularly downwards to the lower border ; 



