BIVALVIA. L2E 
21. Nucuna THanatrana, Hdwards, MS. Tab. XIX, fig. 6. 
Spec. Char. NV, testd ovato-trigond, convewiusculd, tenui, valde inequilateral, radiatim 
striata ; striis tenuibus, sub-decussatis ; lunuld nulld aut indistinctd ; ano plano, levigato ; 
cardine crassiusculo, umbonibus minimis ; marginibus dorsali et ventral converiuscws ; 
margine ventrali crenulata. 
Shell ovately triangular, rather convex or tumid, thin, very inequilateral, and covered 
with radiating strie ; strie fine and irregularly decussated ; no distinct lunule ; siphonal 
or anal region flattish and smooth ; hinge rather thick, umbones small ; dorsal and ventral 
margins slightly and nearly equally convex; margins crenulated. 
Length, ¥ an inch. 
Locality. Pegwell Bay (Adwards). 
The figure above referred to was taken from an unique specimen in Mr, Edwards's 
cabinet, of which the umbo was not quite perfect; it represents the shell as rather more 
elongated than it ought to be. 
22. Nucuna rumescens, Hdwards, MS. Tab. XVIII, fig. 1 a—e. 
Spec. Char. NN. testd ovato-trigonuld, tumescenti, crassiuscula, levigatd, obsolete 
radiata ; pedi-regione sub-cuneatd; siphoni-regione brevissimd, truncata ; umbonibus ter- 
minalibus, depressis ; lunuld indistinctd ; marginibus crenulatis ; dentibus numerosis, ad 
apicem decrescentibus. 
Shell ovately triangular and wedge-shaped, tumid, rather thick, and smooth; pedal 
region obtusely wedge-shaped ; siphonal region very short; exterior obsoletely rayed ; 
beaks terminal, depressed ; lunule indistinct ; anal region marked with an obtuse elevation 
or ridge; margins crenulated ; teeth numerous, decreasing towards the umbo. 
Length, } an inch; height, 3ths of an inch. 
Localities. Mead End, Barton (Zdwards). 
This is not rare. The principal distinction of the species is its great tumidity, thereby 
giving more than ordinary depth to the interior of the umbonal region. 
23. Nucuta Wervereuuil, J. Sowerby. ‘Tab. XIX, fig. 9 a, 3d. 
Nucura WETHERELLII. J. Sow. Geol. Trans., 2nd ser., vol. v, pl. viii, fig. 12, 1834. . 
— — Prestwich. Geol. Journ., 1847, p. 405. 
-—- -- Morris. Catal. Brit. Foss., p. 218, 1854. 
