60 OLIVJN^E. 



nucleus. Shell oliviform, polished ; spire produced, acute, suture canal- 

 iculated ; aperture narrow behind, enlarged anteriorly ; coluraella plicated 

 in front, callous posteriorly. Dentition, PI. 12, fig. 14. 



OLIVA, Brug. 



Tentacles enlarged at the base ; mantle with a posterior filament lodged 

 in the channeled suture of the spire ; foot long and acuminate behind, 

 shield with the side-lobes tapering, acute, small. Operculum none. Shell 

 oblong, subcylindrical, polished ; spire short, conic ; suture canaliculated ; 

 aperture long and narrow, anteriorly widely notched ; < olumella obliquely 

 plicate, sulcate or striate in front, posteriorly callous ; outer lip simple. 

 Dentition, PI. 2, fig. 12. 



Subgenus LAMPRODOMA, Swainson. 



Spire acuminate, elevated, suture canaliculated ; inner lip simple poste- 

 riorly, but regularly numerously plicate anteriorly, the plicae more 

 transverse than in the typical group. 



Subgenus CALLIANAX, H. and A. Adams. 



Shell swollen, ovate, with short conical spire and channeled sutures ; 

 aperture wide, effuse in front ; inner lip with a very thicTc, defined callus, 

 and a few, frequently indistinct, anterior plaits. 



Subgenus AGARONIA, Gray. 



Shell thin, oliviform, but a little effuse anteriorly ; spire acuminate, 

 suture channeled ; aperture rather wide, effuse anteriorly ; columella not 

 thickened posteriorly, tumid, with a few oblique plaits in front, Operculum 

 distinct. Tortoliva, Conrad ; T. Texana, Cour. (PI. 3, fig. 30), is a synonym 

 of Agaronia. It is an eocene fossil from Texas. Dentition, PI. 2, fig. 13. 



Subgenus OLIVANCILLAUIA, d'Orbigny. 



Head and tentacles concealed; mantle with a large, thick, fleshy 

 appendage behind, partly covering the spire ; foot very voluminous, 

 truncate posteriorly, shield with the side-lobes very large and rounded. 

 Operculum present, small, half ovate, with subapical nucleus. 



Shell smooth, wide oblong, last whorl swollen ; spire very short, the 

 suture not canaliculated to the apex ; aperture rather large and wide, 

 inner lip somewhat tortuous, with a large callosity behind, incurved in 

 the middle, and two or three ooli-que anterior plaits. 



The last three subgenera appear to connect the typical Olives with the 

 Ancillariaa, in a regular series of stages of both animal and shell, as well 

 as in the presence 01 an operculum. 



PLOCHEL^BA, Gabb 



Shell olive-shaped, suture nearly obsolete as in Ancillaria ; aperture 

 linear, deeply and obliquely notched at the base, as in Dibaphus ; outer 

 lip thickened internally in the middle ; inner lip callous and having 

 several transverse folds, of which the upper are the smallest; columella 

 strongly recurved at the base. P. crassilabra, Gabb. PI. 3, fig. 22, 

 Tertiary, W. 



