Casey — Notes on the Pleurotomidae. 133 
The European Miocene fouaultia Bell., seems to share 
some of the characters of both Plewrolirta and Gemmula, but 
has the peripheral carina greatly expanded and crenulate, 
giving it the general appearance of Cochlespira, with which 
it was confounded by Cossmann. It however differs com- 
pletely in the form and position of the anal sinus, Ltowaultia 
having the sinus on the expanded peripheral carina, as in the 
two genera mentioned, while in Cochlespira it is situated on 
the concave fasciolar surface between the periphery and suture. 
Gemmula Weink. 
According to the definition given by Cossmann (Kssais de 
Pal. Comp., 2 Livr., 1896, p. 62) there would seem to be no 
reason to doubt that P. denticula, the type of Hemipleurotoma 
Coss., belongs to the same group of species as the living 
kieneri Doum., monilifera Pease, and several others, in fact 
the latter is so similar to the American Eocene and Oligocene 
amica and rotaedens, that, following the views of some authors, 
it might be considered a mere variety. Although I have not 
seen gemmata, the type of Gemmula, it is assumed to be en- 
tirely congeneric with kieneri, fusca, gilchristi and monilifera, 
which are before me, these four species representing the most 
typical form of Gemmula in retaining the denticulations of 
the peripheral carina throughout the growth of the shell. 
The living albina Lamk. and deshayesi Desm. are somewhat 
aberrant in having the denticulation of the peripheral carina 
confined to the very young or nepionic whorls and gradually 
becoming lost on the larger whorls, as in the American fossil 
alternata, of Conrad, and some other species. The genus 
will prove to be very extensive, retaining all essential charac- 
teristics of form and sculpture from the very early Eocene to 
the present time, and there will probably prove to be at least 
30 species in our Eocene strata alone. The species of Gem- 
mula vary in size from relatively small to distinctly above the 
average of the tribe, and resemble Plewrotoma in being devoid 
of true ribbing or visible lines of growth, in general form, 
and in the development of spiral carinae, but differ in having 
