BIVALVIA. 119 
18. Nucuna spHEnoipEs, Hdwards, MS. Tab. XVIU, fiz. 2, and Tab. XIX, fig. 2 a, 4. 
Spec. Char. N. testa minutd, irregulatim trigond vel sphenoided, tumidd, levissina, 
politd ; pedi-regione ovato-angulatd ; siphoni-regione brevissimd, truncatd ; ano distincto, 
circumdato, in medio prominenti ; lunuld elongata, depressd, divisd ; margine dorsali sub- 
arcuatd ; margine ventrali convexd ; marginibus crenulatis. 
Shell small, roundedly triangular or wedge-shaped, tumid, smooth, and glossy; pedal 
region obtusely pointed; siphonal region very short, with a prominent anal corselet 
surrounded by a depression ; ventral margin very convex, with the edges crenulated. 
Length, ¢ths of an inch. 
Localities. Hempstead, Brook? (%dwards). 
A few specimens of an elegant little species enrich the cabinet of Mr. Edwards, and 
there is attached to them the above name in MS. ‘They very closely resemble a species in 
the Paris Basin figured and described by M. Deshayes under the name of WV. Greppini, 
especially the specimen represented by fig. 2, Tab. XIX, and when the specimens them- 
selves are compared they may possibly prove to belong to the same species, but I have 
not the means of doing this. ‘There is, however, an apparent difference, which I may here 
point out. Our shell has the dorsal margin less curved, while the ventral margin is more 
so, than is represented in the figure of V. Greppini, Desh., p. 882, pl. Ixiv, figs. 13—16 ; 
and it has a distinct lunule or dorsal depression, divided by a slight central ridge, and 
it is more tumid. The anal region also has apparently a more prominent centre and 
deeper external depression. 
19. Nucuxa sericea, S. Wood. Tab. XIX, fig. 3. 
Spec. Char. N. testd tenui, transversd, subtrigonuld, levigatd, glabra, calvatd aut 
obsolete radiata ; pedi-regione producta, angulatd ; siphoni-regione obliqué truncatd, sub- 
attenuata ; lunuld inconspicud ; margine dorsali conveatusculd ; margine ventralt arcuatda ; 
umbonibus acutis, terminalibus ; marginibus crenulatis. 
Shell thin, transverse, subtrigonular, smooth, glossy, naked, or with obsolete radiating 
striae ; pedal region produced and angulated; siphonal side obliquely truncated, and 
somewhat pointed; lunule inconspicuous; dorsal margin slightly convex, ventral margin 
more curved; beaks terminal; inner margins crenulated. 
Length, } an inch. 
Localities. White Cliff, Hunting Bridge (Adwards). 
This species somewhat resembles prelongata and protracta, but it protrudes more on 
the siphonal side, and the ventral margin is more rounded. It differs also in the anal 
