﻿DALL] REVIEW OF FROG-SHELLS AM) TRITONS 137 



There is a considerable Polynesian group of these normally de- 

 collated species. 



Section Tceniola I 'all, nov. 



Type Triton decollatns Sowerby, Polynesia. 



Shell small, subcorneal, the nepionic shell normally decollate; first 

 subsequent whorl or two with faint axial ribs, the remainder with 

 only sharp deep sulci between strap-like smooth spiral ribs; a single 

 prominent and terminal varix ; suture appressed, coloration in con- 

 tinuous spiral lineation. Operculum? 



The sculpture of this and one other form is in such sharp con- 

 trast to that of the other species of the genus that it seems as if it is 

 entitled to a sectional distinction. 



Subgenus Phrygiomurex Dall, nov. 



Type Triton sculpt His Reeve, Polynesia. 



Shell small, frequently truncate at the apex, nucleus smooth, visihle 

 part subconic or turbinate, test fusiform, not torticular, with suhacute 

 spire and short recurved canal ; whorls axially ribbed, the posterior 

 ends of the ribs coronating the suture, the interspaces filled with thin 

 crisp axial lamellae closely crowded, crossed by spiral threads and 

 forming a sort of superficial lacedike coating to the shell, recalling 

 that of Scata cochlea Sowerby, or unworn Aspella; varices irregu- 

 larly disposed, callus of the aperture not conspicuous, operculum 

 narrow, muricoid, the nucleus mid-lateral. Color whitish. 



The type species has a deep spiral sulcus on the base, bordered by 

 two strong revolving ribs and crossed by the anterior ends of the 

 ribs, thus forming conspicuous pits; there are from one to three 

 varices, chiefly on the last whorl. In Triton antiqiiatits Hinds, which 

 seems to belong to the same group, the shell is more cylindric, the 

 ribs fainter, the anterior sulcus wanting, and the varices occur on any 

 part of the spire ; but are nowhere very prominent. 



This group has so many conchological characters in common with 

 the tritons that one hesitates to separate them, but the peculiar surface 

 recalls Aspella and the operculum is unlike any other among the true 

 Tritons which I have seen. I am inclined to believe that this section 

 will eventually find a place among the true Trophons or near some 

 of the Purpuroid Murices. 



It is noticeable that the canal is never closed in the Septida, and 

 any shell, no matter how superficially similar, with a closed canal may 

 confidently be referred to the Muricidce. But in the cases such as 

 this where the canal is not closed the final allocation must depend 

 upon the characters of the radula. 



