158 Trans. Acad. Sci. of St. Louis. 
Eocene, a slender and much elongated species, with a long 
slender and gradually tapering beak. The series of small 
rounded close-set nodules, forming the subsutural collar, are 
completely independent of the relatively large and oblique 
costae, which are less than half as numerous. The strong 
even spiral lyrae are also a peculiar feature. 
Among other described genera of the tribe Pleurotomini, 
special mention should be made of Hopleurotoma Coss., very 
rich in species in the European Eocene and in the American 
Lower and Upper Claiborne, where it is represented by such 
species as nupera Con. (=rugosa Lea and protapa De Greg.), 
gemmata Con. (=tupis De Greg.), haeninghausit Lea, sayt 
Lea (= monilifera Lea), desnoyersi Lea (=lintea Con. and 
properugosa De Greg.) and nodocarinata Gabb. In Europe 
Borsonia and EHpalxis are well known fossil genera, but 
Cordiera would seem to belong rather to the Pseudotomini, 
as far as disclosed by published descriptions and figures, and 
is apparently not closely allied to Borsonia. The American 
Borsonia plenta belongs to Protosurcula, as stated before, and 
is not related to the true Borsonia, which is exclusively 
European. 
There are some other distinct genera among our fossil 
species which are not further dwelt upon at present, princi- 
pally because of lack of material. Among these types of 
more or less isolated genera may be mentioned Drillia 
prossert Harr. and Pleurotoma plutonica Csy., which are 
congeneric, and the following apparently unique types: car- 
lottae, cainet and texanopsis, of Harris, extloides Ald., nasuta 
Whitf. and lesuweurt Lea. 
CLAVINI. 
This tribe is less extensive than the Pleurotomini, but is 
nevertheless composed of numerous generic groups, which are 
less isolated among themselves than those of the foregoing 
tribe, a condition due in a great measure to the fact — as be- 
fore stated of the non-operculate series, —that the Clavini 
are largely modern in development and include comparatively 
few extinct types. Many Eocene fossils assigned to that most 
