100 



SHELLS AND SHELL-FISH. 



PART J. 



Analogies of the Volutid^ and the Cassid^e. 



Suh-iamilies of 



VoLirrii)-E. 

 Tyjjical Genera. 



VOLUTA. 

 MlTRi. 



OUVA. 

 AjfCILLiRIA. 



Marginella. 



Analogical Characters. 



Smooth; spire short ; base truncate. 

 f Rough ; spire longer j base atte- 1 

 X nuated. i 



f Foot very large ; no distinct plaits > 

 X on the pillar. 3 



Aperture very wide ; the base of 

 the i)illar oftea thickened and 

 striated. 



J" A thick deposition surrounding 

 t the anerture of the shell. 



i 



Sub-families of 



CASsin^. 

 Typical Genera. 



Cassis. 



MUREX. 



buccinum. 



Purpura. 



Nassa. 



This table illustrates what has been often shown 

 among the vertebrated animals, — that, to establish the 

 analogies of two given groups, they must often be traced 

 through the medium of other groups : thus, the Ancil- 

 larice, in one respect, are prototypes of the Cyprcece; and 

 in another, by their wide aperture and striated base, are 

 equally so to the Parpum. Again, if it was asked, — 

 Vyhat shells among the volutes have a marked resem- 

 blance to Concholepas and Monocerob- ? every natural- 

 ist would point to Ancillaria ; for all three have a very 

 wide aperture, and a distinct prominent tooth at the base 

 of the outer lip. This is conclusive evidence ; and it 

 therefore follows that the analogy betw^een AncUkiriii 

 and Ci/pr(va, however obscure in a direct Avay, is ren- 

 dered plain by being traced through the medium of the 

 Furpurince. The other analogies in the table are so 

 palpable to the zoologist, that they require no illustra- 

 tion. Hence it follows, as a natural result of this com- 

 parison, that the Volutidcp, in like manner, represent 

 all other of the circular groups in the zoophagous 

 tribe. 



(90.) Our next object is to show that the Volutidcp. 

 as a whole, form a circle of affinity. It is clear that the 

 pre-eminently typical volutes, or melon-shells, branch 

 off into two separate series ; — one leading to Scaphelhi, 

 through F. magiiifica, falgetruni, papillaris, and fuai^ 



