24 Mode of Progression in the Genus Lima. 



possesses this singular mode of progression.* If I mistake 

 not, however, the genus Cypris (a crustaceous animal with a 

 bivalve shell) swims in a manner somewhat analogous. 



The animal of the Lima which I noticed at Malta is of a 

 delicate pink colour ; the margin of the mantle fringed with 

 numerous slender filaments.^ It is described, in some works 

 on Mollusca, as provided with a byssus ; but of this I could 

 see no traces ; nor is it probable than an animal possessed of 

 such great locomotive powers should have one. Cuvier, in- 

 deed, though aware of its power of natation, assigns it a 

 small byssus. He further asserts that some species of Pecten 

 are able to swim, while others are permanently attached by 

 their byssus. 



Now, it appears to me, that the great locomotive powers 

 of the Lima betoken an organisation so different from that 

 of those Pectines which remain constantly rooted to one spot 

 by their byssus, as to make a wide interval between these two 

 genera. It is desirable, therefore, to learn whether this in- 

 terval really exisits, or whether a passage may be traced 

 between the locomotive and the attached species of Pectinidae. 

 I have, therefore, drawn up the following queries for the con- 

 sideration of your conchological readers : — 



1. What are the natatory species of Pecten to which Cuvier 

 alludes? 



2. Do they possess a byssus ? If so, can they attach them- 

 selves spontaneously? or are they attached at any definite 

 period of their existence? 



3. Do these natatory Pectines exhibit any generic or sub- 

 generic difference from the attached species ? 



4. Do the attached species become detached at certain 

 periods of life, or can they detach themselves spontane- 

 ously ? 



5. Are there any species of other byssiferous genera, such 

 as A'rca, Pinna, &c, which are constantly or occasionally 

 detached and locomotive ? 



6. Do any species of Lima possess a byssus ? If so, are 

 they either permanently or occasionally attached ? 



Lastly. If it should appear that the whole genus Lima is 

 destitute of a byssus, and is permanently locomotive ; and 

 that all the other genera with which it has been hitherto 

 classed possess a byssus, and are permanently attached ; what 

 other organic differences characterise the genus Lima ? and 

 where ought it to be placed in a systematic classification ? 



* This singular locomotive property is not peculiar to the genus Lima. 

 — Ed. 



