148 CORBULID. 
A. PR&TENUIS, Pulteney et nobis. 
Cochleodesma, Couthouy. 
C. pretenue, Brit. Moll. 1. p. 235, pl. 15. f. 4. 
As the animal of this species varies in no material cha- 
racter from our type, we refer to our account of it im the 
‘British Mollusca,’ which volumes we suppose to be in the 
hands of every cultivator of this branch of natural history. 
The specialties of the shell are not of moment im a generic 
point of view. The ossicle is large, and more apparent than 
usual. 
A. pistorta, Montagu et nobis. 
Thracia distorta, Brit. Moll. i. p. 231, pl. 17. f. 1, 2, 3, 8; (animal) 
pl. Hote 5. 
For an account of this animal, we refer to notes of ours m 
the ‘ British Mollusca.’ 
The ossicle is the most minute of the tribe. 
A. convexa, Wood et nobis. 
Thracia convexa, Brit. Moll. i. p. 229, pl. 16. f. 1, 4. 
We have not seen the animal of this species, but cannot 
doubt that it marches with its congeners. We have shells in 
our collection containing the usual arcuated ossicle. Small 
shells are frequently met with at Exmouth, but those of 
2 inches transverse measure are very rare. 
CORBULID. 
This little group consists of three genera, Corbula, Sphenia, 
and Pandora; the first has only one established species ; 
Sphenia, one ; and the last, two; one of which is probably not 
indigenous. The Corbulide, by the closed mantle and short 
united siphons, are allied to the Anatinide and Saxicave. 
