CHAP. V. 



ANALOGIES OF THE STROMBIN^. 



143 



Genera of 

 Strombin^. 



Pterocera. 

 Strombus. 



Strombidea. 

 Rostellaria. 



Aporrhais. 



Analogies of the Genej'a of the ^trombi^: je. 



Analogies. 



Sub-families of the 

 Strombid^. 



Outer lip greatly dilated, andlobed. Strombin^. 



rOuter lip detached above, and en- 7 rQ»Tj^„ 

 I tire. j 



rOuterlipnot detached, but gib- '^ 



•< bous ; both lips thickened, and >CoLUMBELLiN5i. 



C. generally striated. j 



vShell long, slender, fusiform. Pleurotomin^e. 



'Shell club-shaped when young; 

 channel very short, and 

 sted on one side. 



r Shell c 

 < the 

 C. twist 



Ijc 



ERITHIN^. 



These variations take place in precisely the same or- 

 der as that in which the relations of affinity occur ; for 

 each of these columns is a circular group, — the genus 

 Aporrhais being as much connected to Pterocera as to 

 Rostellaria. Turning to the other group, we perceive 

 the very same affinity between Cerithium and Strombus, 

 through the medium of Aporrhais, as between Cerithium 

 and Pleurotoma. The resemblance between Strombidea 

 and the typical ColumheUincE, again, cannot be mistaken ; 

 for the outer lip of both forms a sort of angle or gib- 

 bosity, altogether peculiar to these two groups. This 

 remarkable thickening, in short, of the lips in Strombidea, 

 renders the genus a prototype of the Colunibellince, as 



well as of the Mar - 

 ginellince. Rostella- 

 ria and the Pleuro- 

 tomincE are the only 

 fusiform groups in 

 the whole family ; 

 while the likeness 

 of a young Apor- 

 rhais to the Ceri- 

 thincB need not be 

 dwelt upon. The 

 resemblance between such shells as Strombus Luhuanus 

 {fig. 1(). a), when young (6), and Conns amadis (c), 

 and others, is so great, that an unpractised eye can 

 hardly tell the difference. 



