12 Mr. E. Liovett on Abnormal Forms and 



I, however, know of a sand-bank on the Jersey coast, which I 

 visited at low tide on one occasion, where I found this rarity in 

 such abundance that I have no hesitation in saying that I could 

 have filled a bushel basket with them in a very short time. The 

 other case was that of a crustacean, Stenorhynchiis Egyptius, 

 which had not hitherto been described as British. A dredger 

 brought up, amongst other material, about a hundred of this 

 species, until then never seen in our seas. 



Now to revert to the common mollusc already referred to. It 

 is Patella vulgata and its allied Patella athletica, the limpet, a 

 very common shell, or rather a shell which lives in such a 

 position as to be met with by man. I consider it possible, too, 

 that if a very large collection of Patellas was made, from every 

 possible locality, it would perhaps be difficult to say where 

 P. vulgata left off and P. athletica began. The observation I 

 made with regard to this species was this, that where the animal 

 was fixed to a rock in such a position as to receive the full force 

 of the sea, the form of the shell was conical or elevated, whereas 

 the shells of animals fixed upon flat shelf rocks, or upon the 

 sides of gullies, where the impact of the sea affected them 

 laterally, were much more flattened or compressed. 



It is obvious that vertical force is best resisted by a tall or 

 conical form, and lateral force by a flat one ; in other words, 

 unless these Patellas had adjusted their structure to their external 

 relations during their growth they would probably have ceased 

 to exist at all, but, having done so, they part company as regards 

 similarity in form ; and it would not be a very unwarrantable 

 thing for a species-making naturalist to call one Patella depresm 

 and the other Patella elevata. 



Another mollusc, very largely sought for and met with, and 

 therefore called common, is the whelk, Buccinum undatum, 

 (I select common species, because we see more examples, and 

 therefore understand the pros and cons of their variations better.) 

 This species is very largely obtained from the North Sea, and it 

 develops a remarkably fine shell, and, in fact, seems to be in 

 complete correspondence with its surroundings on the Dogger 

 Bank. 



Now, if we go south to the Channel Islands, where so many 

 fine and beautiful MoUusca occur, we find Buccinum a weakly, 

 puny shell, as unlike a good North Sea whelk as two species ; 

 so that it is evident that the bright warm waters of the sunny 

 south are, for some reason or other, not in complete cor- 

 respondence with the internal relations of this species ; hence 

 a marked variation which might, with very little imagina- 

 tion, become a named variety, and then, of course, another 

 species. 



Another common mollusc, the mussel, Mytillus eduUs, is very 



