LITHODOMUS. 



Cuv. 



TESTA transversa, sequivalvis, regularis, elon- 

 gata, (valvis clausis) cylindrica, extremitatibus 

 pariter rotundatis, latere antieo brevissimo; 

 epidermide fusca, cornea induta: umbonibiis 

 anticis, poene prominulis. Cardo linearis, eden- 

 tulus. Ligamentum lineare, internum, parte 

 minima externe conspieua. Impressiones mus- 

 eulares duie, antica minima, postica majus- 

 cula, oblonga. 



Separated from tlie Modiola by Cuviei% (Regne Animal 

 II. p. 471 ), on account, as its name implies, of its living 

 in stones, but reunited to them by Lamarck, who, not- 

 withstanding their peculiar and different habits, discovers 

 in these shells only true Modiolce. Now, as we are of 

 opinion that nature has given to each animal an organiza- 

 tion precisely suited to its habits, or in other words, that 

 the habits of each animal are always the consequence of 

 its peculiar structure, and knowing as we do that the 

 Lithodomi are constantly terebrating animals, we accord 

 with the first named author in separating them from the 

 ModiolcE; and we are the more disposed to do so, because 

 they may also be easily distinguished by the peculiarities 

 of their form ; but we are at a loss to conceive how the 

 accurate Ciwier could have made the following remark 

 Upon the Lithodomi: " lis se suspendent d' abord aita,' ^'lerres, 

 comme les monies communes, mais ensuite ils les percent 

 pour s'y introduire, et y creusent des cavites^ dont ils ne 



