QO ORDERS AND FAMILIES. 



ADEORBID^;. Shell small, porcellanous, depressed, circular or ear-shaped; 

 umbilicus wide, operculum horny ; spire depressed, mouth obliquely 

 rhombic, angulated above and emarginate below. Adeorbis, 438. 



APORRHAID^;. Shell with outer lip dilated ; spire turreted and tapering ; 

 no umbilicus, operculum pear-shaped. Aporrhais, 455, 456. 



ASSIMINEID^:. Shell small, conoidal ; spire short ; mouth roundish oval, 

 inner lip thick, outer lip sharp ; operculum horny, nucleus on inner 

 side of mouth. Assiminea, 432, 433. 



BUCCINID.E. Shell fusiform, thick, ridged; spire short, body whorl 



large ; mouth oval, pillar twisted ; canal short and curved back ; 



operculum horny and never spiral. Bnccinum, 517, 518 ; 

 Buccinopsis, 519. 



C.ECID^E. Shell a cylinder curved or straight, the spire being lost when 

 young ; operculum horny, circular with a central nucleus. Cacum, 

 453- 454- 



CAPULID.^E. Shell patelliform, spire small; generally an internal plate to 

 which the adductors are attached;, no opsrculam. Capulus, 382; 

 Calyptraa, 383 ; Crepidula, 384. 



CERITHIIDJE. Shell long, spire tapsring to a fine point ; whorls many, 

 generally tuberculate, varicose or spiny ; mouth small, sometimes 

 strongly channelled ; groove at base short and recurved ; no umbilicus. 

 Cerithium, 443 to 446 ; Cerithiopsis, 447 to 451. 



COLUMBELLID^E. Shell small, fusiform, mouth narrow, canal short and 

 deeply notched, outer lip thick and sinuated ; pillar with one fold at 

 base; operculum horny. Columbella, 511, 512. 



CONID^. -Shell fusiform ; spire tapsring or turreted ; mouth narrow and 

 oblong; outer lip notched at or near suture, pillar smooth, canal 

 nearly straight. Mangilia, 530 to 535 ; Pleurotoma, 536 to 549. 



CYCLOSTOMATID^E, Shell spiral ; spire elevated ; mouth circular or nearly 

 so ; umbilicus small and narrow ; operculum solid. Cyclostoma, 397. 



CYCLOSTREMATID^E. Shell discoidal, cancellated ; mouth nearly circular ; 

 umbilicus wide ; operculum spiral, calcareous. Cyclostrema, 335 to 337. 



CYPR^ID.E. Shell convolute, solid, spire hidden ; mouth long, straight, 

 narrow, toothed at sides, channelled at ends, outer lip folding inwards. 

 Cypma, 457 ; Ovula, 458. 



EULIMIDJE. Shell subulate, small and long, with many whorls : spire 

 finely tapering ; mouth pyriform ; operculum horny, with nucleus on 

 inner side. Eulima, 461 to 466 ; Stilifer, 467. 



FASCIOLARIID^E. Shell fusiform, spire long and tapering; throat and 

 pillar smooth ; pillar curved ; canal often very long ; operculum 

 horny; no umbilicus. Fusus, 520 to 528. 



FISSURELLID/E. Shell patelliform, elevated or depressed, with a slit in the 

 crown, in front of the crown, or on the anterior margin. Fissurella, 

 326, 327 ; Puncturella, 328 ; and Emarginula, 329 to 332. 



