60 University of Michigan 
the last teeth present show that they are very near the outer 
edge of the radula. 
These differences in the sculpture of the shell and in the 
radula seem to warrant the separation of H. sumichrasti 
Crosse and Fischer (1872) as the monotype of ‘a new sub- 
genus, Miraverellia. The descriptions of the shell-sculpture 
and of the radula, given above, separate this group from Tri- 
chodiscina von Martens (1892), of which H. coactiliata Ferus- 
sac (1838) is the type. The radula of Averellia Ancey (1887), 
in the strict sense (type H. macneili Crosse, 1873), has not 
been examined, but this typical subgenus is separated distinctly 
from either of the others by the peculiar, lamella-like infold- 
ings of the last whorl; the shell-sculpture is closer to that of 
Trichodiscina. 
