Casey — Notes on the Pleurotomidae. 159 
astonishing complex known as Drillia, do not belong even to 
the present tribe and are true Pleurotomids. The genus 
Drillia is in reality very limited, and, as far as known to me, 
includes only its West African type species described by Gray 
under the name wmbilicata. The Clavini may be considered 
to possess three principal types of structure or general facies 
represented by Clavus, Crassispira and Drillia, but the 
definition of genera in these sections will prove to be an 
uncertain and rather unsatisfactory matter. The genus 
Cymatosyrinx Dall, is a rather isolated fossil type, and is 
truly represented only by dunata Lea, and a few other species 
of our upper Tertiaries, having a peculiarly short, broad and 
obtuse paucispiral embryo and an external oblique rostral 
ridge. Many of the species placed with the type, even by 
its author, do not belong there. Cossmann assumes the 
name Cymatosyrinx for the old and very extensive genus 
Clavus, on the ground of preoccupation, because of the older 
name Clava Gm., but this is evidently inadmissible, Clavus 
being abundantly distinct from Clava, and if such generic 
words as these were not held to be distinct, very great con- 
fusion in zoological nomenclature would result. The species 
figured by Tryon in his ‘* Structural and Systematic Concho- 
logy’’ as a typical Drillia, the gibbosa of Kiener, does not 
even belong to that section of the tribe, but should form the 
type of a genus closely allied to the true Crassispira as rep- 
resented by the West Indian dottae Val. and the West African 
callosa Val. and carbonaria Rve. Although the shells in 
this tribe are generally thick and heavy, it is remarkable that 
some of the largest and heaviest of them, such as the three 
species of Crassispira just mentioned, are seldom or never 
found perfect when mature, but are invariably largely and 
roughly decollated. The following genus seems worthy of 
definition at the present time, as it is quite isolated and one 
of the oldest known types of the Clavini. 
Eodrillia n. gen. 
The typical forms of this genus are characterized by a 
smooth, or at most finely and spirally striate surface, well 
developed, more or less rounded ribs, which do not cross the 
