CHAP. IV. VOLUTA TYPES OF FORJU. 115 



Analogies of the Types of Voluta to the Zoophagous 



Trihe. 



Types of 

 yoluia. 



T • 1- ^ J- 7 ("Spines often largeand acute: 7 Af„„. .^:^ 



Impenahs. Cyynbwla. \ ^pi^e muricated. 'JMuRiciDf. 



vi . . ir ■ . f Spire vervshort, smooth; apex 7 Ti..„„,„„, .„_ 



Neptuni. yoluta. { %iiiary ; plaits distinct, j TuRBiNELLiDiE. 



Magnifica. ScapheUa. Mantle very large. Volutid^. 



Angulata. VolutiUthes. { '^^^^^^^^^ '*'"" '°''^'^'^ ^'^*^ ] Cvpr^id*. 



... TT > f Outer lip strongly angulated 7 o... _ 



Scapha. Harpula. J or elevated on the spire. j Strombid^. 



This table brings out two remarkable facts. — The first 

 relates to the analogies of Voliita Scapha and of Har- 

 pula to the StromhidcB — all which^ by placing these three 

 groups in separate columns, fall in precisely opposite to 

 each other. The second relates to the analogy between 

 the Muricidcd and the coronated volutes : these are all 

 the most spiny or muricated of all univalves. The 

 same principle of variation holds good between the 

 smooth melons and the typical Turhinellidce : both are 

 remarkably smooth shells ; both have very short papil- 

 lary spires ; and both have three or four well-defined 

 plaits on their pillar. But the snh-typical group of the 

 TurbinellidcB are composed of those rough, spiny, and 

 often coronated shells, forming our genus Scolymus: 

 these, therefore, are analogous to the sub-typical genus 

 Cymhiola ; and, consequently, to all such forms or types 

 as represent them, as Voluta imperialism Harpula hehrcea, 

 VolutiUthes musicalis, &c. It seems to be one of the 

 laws of variation in the structure of the zoophagous 

 shells, that every one of the families * should contain 

 two prominent groups ; one remarkable for having 

 smooth, and the other rough, or spiny, shells. It 

 would even seem that Nature, so to speak, is so tena- 

 cious of this law, that she adheres to it in the very 

 smallest of her groups, — that is, in the variations of sub- 

 genera. Among the most common instances, the reader 



* Except the CyprccidiB, where it is obvious, from the little variation in 

 the shells, that the analogies must be traced from the animitls cnly. 



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