PLANISPIRA. 113 



Jaw arcuate, smooth (pi. 12, fig. 9, C. dominula). In 0. mac- 

 gregori the lower margin shows traces of denticulation, and the 

 median portion is transversely wrinkled (pi. 12, fig. 11). 



Central and inner lateral teeth with a single cusp, shorter than 

 the basal-plates. Marginals having a long, oblique, bifid mesocone 

 and a small ectocone. 



Genital system like that of Plcmispira on the female side. Penis 

 extremely short, stout, the retractor and vas deferens inserted at its 

 apex (pi. 12, fig. 8, P. plagiochila; pi. 12, fig. 12, P. dominula'). 



In this group the epiphallus and flagellum have evidently been 

 lost by degeneration. The anatomy of several species is known 

 through the researches of Tapparone-Canefri and Charles Hedley. 



The following list of species will probably suffer considerable 

 reduction when sufficient material for comparative study is brought 

 together. 



(Group of P. corniculum). 



P. corniculum H. & J., vi, 291. P. deaniana Ford, vi, 292. 



f kiesneri LeGuill. P. dominula Tap.-Can., vi, 293. 



P. purpurostoma LeGuill., vi, P. macgregori Hedl., viii, 285. 



[177. 



( Group of P. tortilabia'). 



P. tortilabia Less., vi, 294. P. rhodomphala T.-C., vi, 297. 



- torticollis (LeGuill.), T.-C. P. semirasa Mouss., vi, 295. 



gibbosula H. & J. moluccensis Pfr. 



P. plagiocheila T.-C., vi, 295. P. leptocheila T.-C., vi, 296. 



( Group of P. margaritis). 



P. margaritis Pfr., vi, 297. P. expansa Pfr., vi, 298. 



v. zonulella Mouss. anozona Mart. 



P. mersispira Mart., vi, 298. P. quadrivolvis Mart., vi, 299. 



Subgenus ANGASELLA A. Ad. 



Angasella A. AD., P. Z. S. 1863, p. 521, only species, cyrtopleura. 

 Pleuroxia ANCEY, Conchologists' Exchange, ii, p. 38 (Sept., 1887), 

 same type. Not Angasiella Crosse, 1864 (Nudibranchiata). 



Shell depressed, umbilicated, plicate-striate ; whorls 4 to 5, the 

 last wide, deflexed in front. Aperture oblique, oval-truncate, the 

 8 



