Boston Society of Natural Hitory. 389 
ticd, parva; caud& recurvata. Length .3 inch, breadth .08 inch. 
Inhabits Dartmouth harbor, clinging to sea-weed. 
Differs from C. perversum, Lam., in the black sutural ridge, and in 
the position of the middle series of granules; and from Murex ad- 
versus, Montagu, in its recurved canal, its distinct suture and its color. 
Mr. Couthouy concluded his paper on the Osteodesmacea, and also 
instituted a new genus to include shells formerly embraced in genus 
Anatina, but which, having a spoon-shaped hinge, are destitute of an 
ossiculum. He thus characterized it. 
Genus CocHLopEsma. 
Animal oval, compressed, enveloped in a thin mantle, closed by a 
meibrane in front, except at the anterior inferior extremity, where it 
Opens to give passage to a broad compressed foot, extending alon 
the whole inferior surface of the abdominal mass, which is inconside- 
Table; edges of the pallium thickened, and a little rugose ; siphons 
long, slender, divided in their whole extent, and opening separately 
into the branchial cavity. 
Shell transversely oval, thin and fragile, sub-equilateral, convexo- 
depressed, slightly gaping at both extremities, inequivalve, right valve 
more convex, beaks moderately prominent, inchning a little back- 
wards, summits cloven and sub-nacrous posteriorly ; extremities 
rounded, Ligament double, the external very slight and membra- 
hous, the internal received into a horizontal, spoon-shaped process on 
each valve, supported by one or two divergent falciform cost, pro- 
jecting from it obliquely and posteriorly ; muscular impressivns su- 
perficial, remote, the anterior elongated-oval, the posterior smal] and 
Sub-triangular, united by a palleal impression profoundly indented pos- 
teriorly, 
The Anatina Leana, Conrad, is the type of the genus; and the 
Anatina pretenuis, Turton, probably belongs to it. 
Mr. Couthouy then read descriptions of the following new species 
of shells 
UCULA NavicuLaRis. N, testa parva, levi, fragili, ovali, sub- 
®quilaterali, luteo-virescente, anticé rotundata, posticé truncatula, 
herding dentibus octodecim, intus albo-nitescente. Length 41, height 
zo breadth 3, of an inch. Inhabits Massachusetts Bay, vicinity of 
Plymouth. 
Beaks more central and basal outline much more strongly curved, 
than in N. myalis, Couth. 
Buiia tineotata. B. testa parvuld, oblongo-ovata, ferrugined, 
transversim obliqué frequenterque striata, spira, prominula, apertura 
Magna, ad basim valdé dilatat4 et sub-effusd, Length ;4,, breadth 
