MoUtisJcs. 



5883 



and twisting in every direction ; the rich crimson foot and snow- 

 white shell, form an object which, to my eyes, is unsurpassed among 

 the British Mollusca, The animal has the power of darting itself 

 through the water, by flapping the valves of the shell in the same 

 manner as the Pectens. The economy, however, of this mollusk, as 

 found in the Clyde district, is by no means the least interesting part 

 of its history. At Herm I have taken it living free in rock-pools at 

 the Galeomma ground, but in the Clyde it always inhabits a nest ; I 

 say always, because when specimens are found free I am of opinion 

 that the circumstance is merely accidental, from the nest having been 

 broken by the dredge, or from the Lima having voluntarily and tem- 

 porarily quitted its usual domicile. The nest in which the Lima lives 

 is frequently as much as eight or ten inches long ; indeed, I think some 

 which I have seen must have been a foot. It is formed of nullipore, 

 stones, shells and sea-weeds, strongly fastened together by means of 

 byssal threads ; the interior is lined with a thick network of similar 

 threads, the interstices being filled up with slime, so that it forms a 

 smooth tube, in which the Lima takes up its abode, and where it is 

 free from the attacks of fish and crabs, to assaults from which its 

 widely gaping valves would otherwise greatly expose it. Here we see 

 one of the many ways in which Providence provides for the safety of 

 those Mollusca which, if unprotected by some artificial means, would 

 be peculiarly open to attack. We have other instances in the boring 

 powers of the Pholades and their allies, the rapidly burrowing abilities 

 of the Solens, the curiously formed nest of Gastrocha3na, and the 

 great muscular power of the Patellidae, which enables them to cling 

 so tenaciously to the rocks. Forbes and Hanley "have never seen 

 any but full-grown specimens contained in these curious nests they 

 must have been singularly unfortunate, for I have repeatedly found 

 the Lima of all sizes encased alike. There is but one thing I have 

 to say against this interesting molluscan, and that is, the animal has a 

 peculiar, tenacious, and, to me, sickening odour ; after having handled 

 a number of them it is no easy matter to remove the smell from the 

 hands with soap and water, and so strong a hold has the nauseous 

 smell sometimes taken on my olfactory nerves that a whole night has 

 scarcely suflSced to remove the impression. Professor Balfour has 

 informed me that the slime with which the nests are lined is very rich 

 in Diatomaceae, and that its examination will well repay the trouble 

 of the diatomist. 



*Pecten varius. Bute, Ayr, Smith; Lamlash, Lcuidsborouyh, 

 „ niveus. Cumbrae, Smith. 



