120 EOCENE MOLLUSCA. 



region, and it is comparatively shorter. The shell is thin, and there is no perceptible or 

 distinct hinule on the pedal region ; neither is there any distinct corselet. The specimens, 

 which are few in number, adhere firmly to the matrix, and I am unable to see the 

 interior. 



20. Nucula subtransversa, Nyst.? Tab. XIX, fig. 13. 



Nucula subtransveesa. Nyst.? Coq. Foss. Belg., p. 227, pi. xviii, fig. 7, a, b, 1844. 

 — ovata. Id.1 Rech. Coq. Foss. de Hoesselt et Kl. Sp., p. 13, No. 31, 



1836. 

 Potiers et Mick. 1 Catal. de Moll, de Douai, t. ii, p. 120, No. 3, 1844. 



Spec. Char. N. testa transversa, oblongo-ovatd, turgidd, valde incequilaterali, obsolete 

 radiatd; pedi-regione pralongd, paulo attenuatd; viargine dorsali subrectd ; margine 

 ventrali conveaiusculd ; lunula inconspicud ; ano ovalo, in medio prominenti ; marginibus 

 rrenulatis. 



Shell transverse or elongate, ovately oblong, or obtusely wedge-shaped ; very inequi- 

 lateral ; obsoletely radiated ; pedilateral margin slightly pointed ; dorsal margin nearly 

 straight ; ventral margin gently curved ; corselet or anal region ovate, elevated in the 

 middle ; margins crenulated. 



Length, ^ths of an inch ; height, ; 5 ths of an inch. 



Localitg. White Cliff Bay {Fisher). 



The specimen figured enriches the cabinet of Mr. Fisher, who tells me it is not rare, 

 but very difficult to obtain in any degree of perfection. 



I have considered it as identical with the Belgian species, depending entirely for so doing 

 upon figure and description, although the proportions given by M. Nyst do not quite accord 

 with those of our own shell. This is extremely transverse or elongate—more so than any other 

 species from the English Eocene deposits ; and the umbo, which is depressed and much 

 eroded, is at the extremity of the shell, the siphoni-lateral margin forming almost a right 

 angle with the dorsal edge. The outer surface shows distinct but irregular lines of 

 increase, and the nearly obsolete rays upon the specimen are most visible towards the 

 pedilateral margin, as they are described to exist on the Belgian shell. 



M. Nyst points out a distinction which exists between his shell and the one which he 

 considers to be the same from the Paris Basin in the number of the hinge-teeth. Unfor- 

 tunately 1 am unable to ascertain the dental characters of our shell. 



