EMARGINULA. 



TESTA clypeiformis, aut depresso-conica, ob- 

 longiuscula, vel oblonga; subtus cava; vertice 

 postic^ inclinato; margine antico fisso, vel 

 emarginato. Impressio muscularis lateribus 

 latior. 



One of the genera separated by modern eonehologists 

 from the Linnean Patella^ and established beyond eontro- 

 yersy, because the distinguishing marks are not to be 

 found in the shell only, but also in the animal, wherefore 

 it may be instanced as one of the best evidences of the 

 propriety of the observation; that wherever there is a 

 characteristic mark of distinction observable in shells, a 

 corresponding difference may be traced in the animal 

 inhabitant, and at the same time as a proof that a con- 

 chological system should rather be formed from the struc- 

 ture and characters of the animals than of the shells. 

 Emarginula is more nearly related to Fissurella than to 

 Patella, inasmuch as its hranchice are not external, and the 

 little fissure or notch in the anterior edge is only the 

 termination of a narrow canal, that serves the same pur- 

 pose in this shell, as the perforation in the summit of 

 Fissurella. 



It is observable that Lamarck has placed Emarginula 

 next to Parmophorus, without seeming to have remarked 

 the very great resemblance of the animals to each other : 

 we have thought ourselves justified, both by the charac- 

 ters of the shells and of the animals, in uniting them ; 

 this may be objected to, perhaps, on account of the great 

 difference in general form, but we answer, that there are 

 some species of Lamarckian Emarginula, one of which 



