LUCINOPSIS. 133 



the examination of very small specimens, not more than 

 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 If inch 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. UNDATA, Pennant. 



L. undata, Brit. Moll. i. p. 435, pi. 28. f. 1, 2 ; (animal) pi. M. f. 2. 

 Venus undata, Auctorum. 



Animal inhabiting a shell of thin and fragile texture, like 

 many of the Tellina, 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 +he 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, in 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 smalmess 

 of the pedal aperture ; the mantle is produced posteriorly into 

 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 1J 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 



