CHAP. IV. REMARKS ON VOLUTA ANGULATA. 109 



against it. First, it may be urged, that, although the 

 series between the smooth melons and such shells as Vo~ 

 luta Scapha is sufficiently obvious, still, that the Valuta 

 angulata can never follow Scapha. This objection seems 

 well grounded, and certainly deserves attention. We 

 admit that angulata has a spire totally different from 

 that structure which we maintain is typical of the 

 group, wherein we have, nevertheless, placed it. But 

 is there anything extraordinary in this arrangement ? 

 Does there exist, in any one class of the animal king- 

 dom, a natural group, wherein all the species exhibit 

 the whole of the typical characters ? Every naturalist, 

 every systematist, knows full well that no such group is 

 to be found. It has been well said, by one of the 

 most distinguished naturalists that this country has 

 produced, that if a species possesses two out of the three 

 characters of the genus in which it is placed, this is all 

 we can expect ; and the reason of this is obvious : if 

 all the species possessed all such characters, then there 

 would be no gradation of structure no links in the 

 chain of affinity no loss of one structure and there- 

 fore no taking up that of another. Now, all this is 

 diametrically opposed to facts ; for the whole creation is 

 but one connected chain of such graduated progressions, 

 unequal, indeed, yet still graduated. The affinity of 

 Scapha to angulata is not so intimate and direct as 

 many others in the series ; but this is nothing to the 

 purpose, because, as we have just said, affinities may, 

 and do, vary in degree : the question is, whether, be- 

 tween these two shells, there is a sufficient resemblance to 

 constitute any degree of affinity ? When we compare 

 the angulated apertures, the form and proportion of their 

 plaits*, and the thick enamel spread over their spire, 

 we see an affinity which to us is unquestionable. If 

 angulata, in short, had a papillary spire, instead of a 

 pointed one, it would be of the same type or sub-genus 

 as Scapha ! the pointed spire, therefore, was necessary 



* Not their number, for in angulata there is one less. 



