STROPHOMENIDiE. 297 



interspaces of about two or three times their width ; the interspaces are longitudinally 

 grooved by three or four finer lines. In the interior of the ventral valve are two narrow, 

 long, oval muscular depressions, separated by a flattened ridge of moderate width. 

 Length 12, width 17, depth 1^ lines. 



Obs. I regret that the late Mr. Salter neither figured nor described his species. I 

 briefly and very imperfectly describe the shell from specimens so labelled in the Museum 

 of Practical Geology, and I am not quite sure whether Mr. Salter has not mixed up two 

 different species upon the same tablet, as the internal casts (figs. 7 and 8) do not quite 

 agree in shape with the exterior (fig. 6). It would be very desirable that more ample 

 material should be sought for in the locality whence these specimens were derived. 



Position and Locality/. Stroph. arenacea is stated to occur in the Upper Llandovery, 

 at Huntley Hill ; Norbury ; May Hill ; Gunwich Mill, near Alfrick ; Presteign ; 

 Malverns ; Church Stretton ; Tortworth, &c. 



Strophomena simulans, M'Coy. PI. XLII, tigs. 9 and 10. 



LEPTiENA (Strophomena) simulans. M'Coy. Ann. Mag. Nat. Hist., vol. viii, p. 403, 



1851 ; Brit. Pal. Foss., pi. i H, figs. 33—35, 

 1851. 



Strophomena simulans, Salter. Mem. Geol. Survey, vol. iii, p. 269, p. 361, 1866. 



Spec. Char. " Truncato-elliptical ; hinge-line slightly exceeding the width of shell, 

 forming short, rounded, semicylindrical ears, from a more or less pronounced indentation 

 of the lateral margins ; front wide, elhptically rounded, entering [dorsal] valve gently 

 and slightly convex for about nine lines from the beak, and then more rapidly arched 

 towards the receiving [ventral] valve, to a position sometimes nearly at right angles with 

 the rostral portion ; receiving [ventral] valve nearly as concave as the entering valve is 

 convex externally, except near the beak, which is convex ; cardinal area rather low, 

 triangular, and nearly at right angles to the plane of the lateral margins ; foramen broad, 

 triangular, closed by the pseudo-deltidium, except at the apex, where there is a tubular 

 perforation (leaving a little columnar stem-like portion of matrix projecting from the 

 apex of the cast); cardinal teeth [cardinal process] very small, bifid, diverging at 115°; 

 the dental lamellae, originating from them, converge under the muscular impressions, 

 so that their inner, gently incurved edges, touching the shell, diverge at about 65°; 

 muscular impressions undulato-orbicular, about a fifth wider than long, reaching rather 

 less than half the length of the shell ; surface sometimes with a few oblique concentric 

 plicse on the ears, regularly radiated with very fine, slightly irregular striae, about twenty- 

 five to thirty in two lines at six lines from the beak, and at that distance usually 



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