NUCULANA SHARMANI. 199 



" Transversely clavate, width two and a half times the length ; anterior 

 [posterior] side produced into a very long narrow beak, abruptly truncated at 

 the end ; posterior [anterior] side moderate, rounded, surface very finely striated 

 transversely." It is therefore impossible, as in the case of N. leiorhyncha, to 

 say whether this species really is a small specimen of N. attenuata or of N. 

 Sharmani. 



Unfortunately Meek has given the varietal name "attenuata" to a form of 

 N. bellistriata, Stevens, occurring in Nebraska ( { U.S. Geol. Surv., Final Rep. 

 Nebraska,' p. 206, pi. x, figs. 11 a, b, c,). This very little shell is quite distinct 

 from N. attenuata, Fleming, measuring less than half an inch antero-posteriorly, 

 and about one-fifth inch dorso-ventrally ; comparatively the posterior end is very 

 much less attenuated than in the British species. 



The type-specimen of " N. claviformis ? " {attenuata) in the Gilbertson Collec- 

 tion is labelled " Carboniferous limestone, Bolland." From the matrix, I cannot 

 think that it was found in limestone ; Phillips gives Harelaw and Otterburn, 

 Northumberland, as well as Bolland, as the localities of this species, and I suspect 

 that the type specimen came from one of the first two of these localities. This 

 species is distinguished by its transverse form and produced posterior end 

 from N. Sharmani, to which it approaches most closely in form ; the well-marked 

 escutcheon distinguishes it at once. N. stilla is much shorter in the anteropos- 

 terior diameter. 



Nuculana Shaemani, R. Etheridge, jun., 1878. Plate XV, figs. 17 — 22. 



NuctTLANA Sharmani, B. Etheridge, jun., 1878. Quart. Journ. Geol. Soc, vol. 



xxxiv, p. 15, pi. ii, fig. 18. 

 Etheridge, 1885. Brit. Fossils, pt. 1, Palaeoz., p. 288. 



Specific Characters. — Shell transversely produced, slightly clavate, attenuated 

 posteriorly, very moderately convex. The anterior end, of moderate size, shorter, 

 but much deeper than the posterior, has a rounded border passing with a gradual 

 curve into the inferior border, which is gently convex, sloping upwards posteriorly. 

 The posterior border is very narrow and bluntly rounded. The superior border 

 consists of two portions, inclined at an obtuse angle, which meet at the umbo. 

 The anterior part is convex, the posterior concave upwards. The umbones are 

 small, just anterior to the central point ; pointed backwards ; hollowed behind by 

 the concave slope of the shell ; and forming the highest point of each valve. The 

 escutcheon is narrow and not deep ; not marked off from the rest of the valve by 

 a ridge, but the upper and posterior umbonal border is rounded from above 

 downwards. 



