Casey — Notes on the Pleurotomidae. 161 



PSEUDOTOMINI. 



This tribe, composed exclusively of extinct old Tertiary 

 types, is confessedly somewhat artificial in scope. There is 

 a certain general Fusoid habitus common to all, the shell being 

 usually stout in form, with short or obsolete beak and the 

 outer lip is broadly, feebly sinuate posteriorly to the suture, but 

 without a clearly limited notch. Pseudotoma was placed among 

 the Conidae by Cossmann and Cordiera'm the Pleurotomidae. 

 Fusitoma sipho Aid., was described by its author as Fusus 

 siphus and Varicobela smithi Aid., was originally described 

 under the name Strombus smithi, while other species, brought 

 together to form the present tribe, were originally assigned to 

 Fusus, Mitra and Borsonia, showing the doubt and uncer- 

 tainty involving the relationships of the species. My concep- 

 tion of Cordiera is derived from the study of a small species 

 from the " Calcaire grossiere," labeled PL nodidaris Desh., 

 and, if it is a typical representative of that genus as main- 

 tained by Cossmann, there can be no doubt whatever of its 

 very pronounced affinity with our Mitra biconica, of Whitfield, 

 and Borsonia ludoviciana Vgn., which species may be con- 

 sidered as representing Cordiera for the present. As to the 

 relationship between Cordiera and Borsonia, I am forced to 

 assume that there is very little real affinity, but only a super- 

 ficially apparent affiliation due to the plication of the colu- 

 mella, a character which is frequently sporadic and of little 

 or no phylogenetic significance in' the Pleurotomidae. Although 

 the embryo of our Eocene Pleurotoma heilprini Aid., differs 

 noticeably from that characterizing the European type of 

 Pseudotoma, the remaining features of the shell agree very 

 well, and we may conclude that heilprini represents the genus 

 in the American Tertiary, but the species figured by Cossmann 

 under the name Pseudotoma bonellii, is certainly generically 

 different from Ps. intorta Broc, assumed as typical of 

 Pseudotoma. 



Ruscula n. gen. 



The general form of the shell in this genus is short and 

 stout, with a very short stout reflexed beak, rather abruptly 



