﻿126 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



occurs, nearly every recent sectional group being found illustrated 

 by some Miocene species. The only exceptions known to me are the 

 southern type of Priene, and Lotoriiim s. s., which seem, so far, to 

 have been recognized only in the recent state. It should be noted that 

 the southern forms referred by Kesteven to Lotoriiim, for the most 

 part exhibit very peculiar characters in the protoconch. Of the Aus- 

 tralian species figured by him only two (figs. 7 and 8) seem to have 

 a protoconch in the least resembling that of the typical group. It is 

 probable therefore that Cossmann is justified in segregating Austro- 

 triton and Semitriton from the common type. 



In considering the arrangement of the members of the group the 

 dentition, the protoconch and nepionic shell, and the operculum must 

 all be considered in any natural arrangement, and with the possible 

 exception of the last are all more important than the conchological 

 sculpture and form. I regard the number and arrangement of the 

 varices as of very little systematic importance, and the defects of M. 

 Cossmann's arrangement are largely due to his depending too much 

 upon this essentially superficial character, which is, at most, of sec- 

 tional value. 



For the dentition of members of this group we depend chiefly 

 upon the data furnished by Troschel. He has shown that the 

 Ranellas are distinguished from the Tritons very much as is Cassis 

 from Doliitm by characteristic features of the radula. The Ranellas 

 have a rhachidian tooth which is narrow but arcuate and laterally 

 produced, generally with a central large and several small lateral 

 denticles on the cusp and on the base a prominent recurved dentiform 

 plate on each side. In the latter character they agree with Doliuni. 

 The Tritons, however, have a rhachidian tooth less extended laterally, 

 not at all or very slightly arcuate on the base and without basal plates, 

 in the latter feature agreeing with Galeodea and Semicassis. Argo- 

 buccinitin (argus) and Fusitriton (oregonensis) have mutually simi- 

 lar teeth, much more similar than those of Priene (scabra) and Fusi- 

 triton. The latter differs from A. argus only in having the inner 

 lateral simple, instead of denticulate. Septa is separated from the 

 other Tritons by its laterally extended rhachidian tooth with a median 

 inflection in front but without basal plates, recalling that of Cassis. 

 The Ranellas possess no jaw or mandible, but Cassis and the Tritons 

 have it well developed. The operculum is rather variable, as between 

 the various groups, in general tending to the fusoid type with apical 

 nucleus, especially in the Tritons, though the tritonoid Distortrix has 

 the nucleus lateral about midway between the ends recalling that of 

 Cassis; Septa has it subcentral and internal; Cymatium (feinorale) 



