LUCINOPSIS. 188 
the examination of very small specimens, not more than {ths 
of an inch diameter, though it is as correct and full as could 
well be expected from such materials; but the receipt from 
Exmouth of adult lively examples of 14 imch diameter, has 
enabled me to review and add to it several unrecorded features, 
which I think will interest malacologists, and show that this 
peculiar genus has scarcely yet received its precise natural 
allocation; and many important circumstances will be de- 
veloped, which may assist to determine the proper station of 
some other bivalve molluscan groups, by the concatenation of 
characters exhibited by this animal, illustrative of its con- 
nection with them. 
L. unpata, Pennant. 
L. undata, Brit. Moll. i. p. 435, pl. 28. f. 1, 2; (animal) pl. M. f. 2. 
Venus undata, Auctorum. 
Animal inhabiting a shell of thin and fragile texture, like 
many of the Tedline, irregularly subrotund, and not exhibiting 
the decided lenticular form of its shell; the general colour is 
pale pinkish-drab, which, when the animal has been killed by 
hot water, often changes to the various hues of orange, red, 
and brown: this remark is of some importance as regards 
correct description, for under similar circumstances this con- 
dition prevails more or less in all the testaceous Mollusca, and 
particularly in the bivalves. The mantle has its edges sinuated 
or furbelowed, in some examples irregularly jagged, but not 
serrated; the ventral aperture is very contracted, only affording 
space for the issue of a moderately sized foot, im consequence 
of the basal position and very large size of the posterior 
adductor; and though the anterior one is nearer the dorsal 
region, it also, from the length, contributes to the smallness 
of the pedal aperture ; the mantle is produced posteriorly to 
two very long pale orange siphons, divergent and separated to 
their bases; the branchial one is the smallest and longest, 
being in adult examples in full extension 14 inch long, and 
having the extremity margined by a circle of very short, 
minute dark lines, blotches or dots, with 16-20 white cirrhi 
of irregular sizes and lengths; the anal siphon is of rather 
