PLEUROTOMID2®. 155 
of the lingual dentition; conchologically the species belong in 
Fusus. 
Genus ANCISTROSYRINX, Dall, 1881. 
Whorls coneave below the suture; with a wide deep sinus, 
bordered externally by an elevated frill directed backwards. 
Operculum and dentition not described. Only a single species 
known, and its systematic position very uncertain. 
Genus DRILLIA, Gray, 1838. 
Shell turriculated, with longitudinal ribs, and usually revolving 
striz ; last whorl usually short ; spire elevated ; columella with a 
posterior callus; outer lip thick, but not varicose, nor dentate 
within, flexuous, with a well-marked posterior sinus near (but not 
reaching) the suture, and an anterior constriction or sinuosity ; 
canal short, curved, usually narrow. 
Principally distinguished from Pleurotoma by the smaller size 
and short recurved canal. 
Animal with tentacles approaching at their bases and eyes 
near their extremities. 
Distr.— Warm Seas. Fossil, cretaceous, U.S.; miocene, Eur. 
The following, generally regarded as subgenera, will be treated 
as sections in this work :— 
Section CRASSISPIRA, Swainson, 1840. Shell somewhat clavi- 
form, tuberculated ; anterior canal very short; inner lip witha 
thick posterior callus ; outer lip thick within. 
Section Conopieura, Hinds, 1844. Shell coniform; aperture 
narrow, sinuous ; columellar lip callous, canal very short; outer 
lip sinuous, with a profound lateral sinus. 
Section Cravus, Montfort, 1810. Tuberculated or spiny; 
aperture rather large ; outer lip produced below the sinus. 
Section Bracuytoma, Swainson, 1840. Shell strombiform ; 
columellar lip rather thick; outer lip ascending and forming a 
canal-like sinus near the suture. 
Genus SPIROTROPIS, Sars., 1878. 
Shell turriculated, rather thin ; apex obtuse; whorls carinated, 
sinus profound, distant from the suture. Operculum normal. 
Dentition (PI. 33, fig. 53) very distinct ; formula 1—1—1-1-l. 
