MONOTOCARDIA TAENIOGLOSSA 



419 



the sides, channelled at each end, lahiuni inflected; no operculum. 



Jurassic . Genera : Ovula (including Amphipcras, Trans- 



ovula, Cyphoma, Radius, Simnia), Pedicularia, Cypraea (with 

 subg., Cypraeovida, Cypraexlia, and Trivia), and Erato. 



Fam. 39. Doliidar. — Foot expanded, wider and longer than 

 the shell, truncated and thickened in front, siphon very long and 

 narrow ; central tooth with very strong median and small lateral 



Fig. 277. 



-Three stages in the growth of Pteroceras rugosum Sowh., E. Indies, 

 showing the development of the 'fingers.' 



and basal cusps, lateral and marginals bluntly folciform ; sliell 

 ventricose, without varices, spire short, outer lip generally simple, 



anterior canal rather wide, no operculum. Cretaceous . 



Genera : Dolium (subg. Malca, outer lip thickened, denticulate, 

 reflected) ; Firida, mantle with two lateral lobes reflected over 

 part of the shell, shell fig-shaped (Fig. 278). 



Fam. 40. Cassididae. — Foot broad, siphon long (radula, Fig. 

 125, p. 223); shell ventricose, with varices, spire short, outer 

 lip reflected or thickened, anterior canal short, recurved narrow ; 

 oY>erculum semilunar, with ribs radiating from a marginal 



