PTEROCERA. 123 



Genus PTEROCERA, Lam., 1799. 



Properly speaking there is only a difference of convenience 

 between this species and Strombus ; that is, no important struc- 

 tural differences are involved. Pterocera is a stromb having 

 the outer lip on the shell prolonged into long digitate processes 

 resulting from similar digitations of the mantle-margin of the 

 animal. Certain of the strombs, those of the section Eupro- 

 tqmus, for instance, have a tendency to digitation, yet do not 

 bridge the gap between the two groups. The Pteroceri as thus 

 defined, consist of ten species, rather constant in character, 

 confined, as to recent distribution, to the tropical seas of the 

 Indo-Pacific, Australian and Polynesian provinces, and not cer- 

 tainly found in a fossil state. 



The genus has been carefully reviewed by Prof. Theo. Gill 

 (Am. Jour. Conch., v, 120), and I have followed him mainly in the 

 synonymy, and descriptions. As will be seen by referring to p. 

 101 of this monograph, I have adopted two sections for the genus 

 Pterocera; these correspond to genera in Prof. Gill's arrange- 

 ment, the last containing two species (S. chiragra and S. rugosa), 

 whilst the first is synoptically tabulated b}' him as follows: 



I. Lips smooth (my Subsection I. Heptadactylus). 



I a. Body-whorl tuberculated at the angle. 

 Lip reflected ; columella with callus diffused, P. lambis. 



Lip inflected ; columella with callus stratified, P. crocata. 



I b. Body-whorl unarmed at angle, P. bryonia. 



II. Lips rugose (my Subsection II. Millipes). 



II a. Intercalary digitations none. 



Posterior digitation with a basal lobe, P. scorpio. 



Posterior digitation simple, P. pseudoscorpio. 



II b. Intercalary digitations developed. 



Posterior digitation simple, P. millepeda. 



Posterior digitation with a basal lobe 



Labral digitations eight ; labral wrinkles very distinct, 



P. elongata. 

 Labral digitations ten ; labral wrinkles faint, P. violacea. 



The Pterocerse have been monographed also by Reeve. Sowerby 

 and Kiener. 



