622 



GASTROPODA. 



[Pulmonata, 



SYNOPSIS OF GENERA. 



A. Animal and shell spirally coiled, heliciform ; shell external. 



1. Shell depressed, umbilicated, periphery rounded. 



Radula : Central and lateral teeth tricuspid ; 

 marginals with a rnesocone only 



2. Shell depressed or trochiform, umbilicated, rarely im- 



perforate, striate or smooth, sometimes harry. 

 Radula : Central tooth with obsolete ectocones ; 

 laterals with a short ectocone ; marginals with a 

 mesocone only 



3. Shell depressed, openly umbilicated, periphery rounded 



or angled, radially ribbed. Radula : Central tooth 

 tricuspid ; laterals similar, but the ectocone larger ; 

 marginals with a broad bifid cusp 



4. Shell orbicular, spire low or flat, umbilicus narrow or 



closed, radially ribbed, interstices minutely reticu- 

 late. Radula : Central tooth tricuspid ; laterals 

 bi- or tri-cuspid ; marginals with 3 to 5 cutting- 

 points 



5. Shell globose, very thin, imperforate or perforate, peri- 



phery rounded or angled. Radula : Central tooth 

 with a mesocone only ; laterals bicuspid, no ento- 

 cone ; marginals with several cusps 



6. Shell conoidly globose, sub- or im-perforate, striated, 



periphery angled. Radula : Central and lateral 

 teeth with a broad blunt mesodont ; marginals 

 with several cutting-points, the inner bidentate . . 



7. Shell similar to that of TlialassoJidix, sometimes with 



membranous plaits and processes. Radula : Central 

 tooth narrow, tricuspid ; inner laterals without side 

 cusps, outer ones tricuspid ; marginals multicuspid 



8. Shell depressed, narrowly umbilicated, ribbed, periphery 



convex. Radula : Central tooth narrow, with or 

 without side cusps ; laterals bicuspid, no entocone ; 

 marginals multicuspid, inner cusp large 



9. Shell discoidal, openly umbilicated, periphery rounded, 



with low spirals and radial lamellse, points of inter- 

 section with hairs. Radula : Central tooth and 

 laterals tricuspid, the ectocone of the latter larger 

 than the entocone ; inner marginals with 1 bifid 

 cusp, outer ones with several subequal cusps 



10. Shell globose or depressed, umbilicate or imperforate, 



usually with few rapidly increasing whorls, smooth 

 or ribbed, periphery convex, keeled in one species. 

 Radula : Central and lateral teeth usually tricuspid ; 

 marginals with 3, sometimes 4, cutting-points, often 

 coalescing on the outer teeth 



B. Animal limaciform, with subcentral visceral hump ; shell 



small, auriform, thin, covered by the longitudinally slit 

 mantle . 



PHACUSSA. 



THALASSOHELIX. 



GERONTIA. 



ALLODISCUS. 



THERM IA. 



SERPHO. 



TlIKKASIA. 



PHENACOHELIX. 



SUTERIA. 



FLAMMULINA. 

 RAXFURLYA. 



Genus 1. PHACUSSA, Hutton. 1883. 



Ph,ifn*. Hutt., T.N.Z.I., xv, 138; xvi, 205. Type: Zonites (?) Helmsi, 

 Hutt. Phacussa, Pilsbry, Man. Conch. (2), ix, 12. 



Animal elongated ; foot very narrow and long, compressed, not 

 tapering, truncated posteriorly, and with a caudal gland ; mantle 



