BIVALVIA. 113 
in similis, which is its nearest relative. It bears a strong resemblance to V. margaritacea 
of Nyst, ‘Coq. Foss. Belg.,’ p. 229, pl. xvii, fig. 9, a, 6, but the dorsal margin of that 
figure is rather more curved. V. margaritacea, Goldf., ‘Petr. Germ.,’ vol. i, p. 168. t. 
125, fig. 21, a—d, also much resembles it. 
Some specimens in Mr. Edwards’s cabinet from the same locality have attached to them 
the MS. names of guadrans,'Vab. XVIII, fig. 8, a, 4, and planiuscula, same plate, fig. 9 ; 
they differ in outward form, as those names indicate, but I think they are varieties of the 
above. It is possible they may prove to be distinct. 
9. Nucuta Heapongnsis, Forbes, MS. Tab. XVIII, fig. 3, a, 3d. 
Nucuta Heaponensis. Morris. Mem. Geol. Surv., p. 156, pl. 6, figs. 12, 12, a, 6, 1856. 
— Id. Catal. Brit. Foss., p. 218, 1854. 
Spee. Char. “ Testa ovato-transversd, depressd, levi, latere antico brevi, subproducto, 
margine arcuato, postice angusto, margine ventrali subarcuato, intus crenulato; lunuld 
prominuld, sulco perspicuo circumdata.” 
“ An ovately transverse and somewhat depressed shell, with the anterior margin short 
and slightly produced, the posterior extremity narrowed, the ventral margin arched and 
internally very finely crenulated ; the lunule prominent, and surrounded by a conspicuous 
furrow.” —Morris. 
Length, *ths of an inch. 
Localities. Colwell Bay, Headon Hill (Morris and Edwards), Hordwell (8. Wood), 
This species has been separated from sémilis by the late Edward Forbes; it has also 
been considered by Mr. Morris as distinct, and I readily acquiesce in the separation. 
Specimens are not particularly rare, and are found often in a very perfect state of preser- 
vation. It somewhat resembles in outline WV. Divoni, but it is a smaller species ; the siphonal 
region is shorter, and the basal extremity on that side is more rounded, and it appears also 
to be a thicker shell. In the ‘Catal. Brit. Foss.,’ p. 218, 1854, Nucula similis, Wood, is 
given as a synonym to this species, but I have not been able to find the reference. 
10. Nucuna uissa, Hdwards, MS. Tab. XVIII, fig. 4, a, 4. 
Spec. Char. NV. testd elongato-ovatd, tenui, levi, glabra, compressiusculd, inequilaterali ; 
pedi-regione latiore, ovata ; siphont-regione oblique truncatd, subrostrata ; marginibus dorsali 
et ventrali convents ; lunuld lanceolato-elongatda, depressa ; ano cordiformi ; dentibus ad apicem 
gradatim minutissimis ; marginibus integris. 
Shell elongately ovate, thin, smooth, and glossy, slightly compressed, inequilateral ; 
pedal-region the wider and ovately rounded; siphonal region obliquely truncated ; dorsal 
