458 



NOTES ON PROSOBRANCHIATA, 



Believing that it is the best form in which to put matter of 

 this kind, I have tabulated these differences of opinion. 



The Apices. 



Becent species. 



It is here shown that the apices do not present a feature on 

 which the species of the genus can be grouped. Twenty-six 

 protoconchs, including nine of fossil species, are figured and 

 described ; and descriptions of a few others are culled from 

 various sources. The species are from all the groups except 

 Lotorium. I have found, as might have been anticipated, that 

 species conchologically very similar have similar apices. It has 

 not, however, followed that species conchologically dissimilar have 

 dissimilar apices. L. succinctum, Lamarck, has an apex exactly 

 the same as that of L. exaratum, Reeve; and the apex of L. 

 pileare, Linn., differs very slightly from that of ves^Mceum, Reeve. 

 The protoconchs of the recent species are all of one type, differing 

 from one another in the number and convexity of the whorls and 

 in colour. They consist of a thin coating of lime inside a corneous 

 original. The lime is apparently not generally deposited until 

 the mollusc starts the adult structure. Protoconchs of L. 

 spengleri, Chemn., and L. exaratinn, Reeve (?), to which no adult 

 structure was attached, were not acted upon in an}'- way when 

 immersed in pure hydrochloric acid. That the corneous coating 

 is only outside, not inside as stated by Reeve (30), is proved by 



