DIOTOCARDIA RHIPIDOGLOSSA 



409 



surface spirany Urate, scaly, spinose, nmbilicate, peristome con- 

 tinuous. Single genus, Dcli:)liimda. (iv.) Umljoniinae. — Eyes 

 pedunculate, left tentacle attached to a frontal appendage, mantle 

 reflected over edge of aperture, lateral teeth 6 on each side ; 

 shell polished, peristome incomplete, umbilicus generally closed 

 by a callosity. Principal genera : Umhonimn, Ethalia, Isanda, 

 Camitia, Uvihoiiella , Clirysostoma. 



Fam. 6. Turhinidac- — Epipodial line with slender cirrhi, snout 

 broad, short, eyes pedunculate at outer base of tentacles, a frontal 

 veil between tentacles ; shell turbinate, solid, aperture continuous, 

 operculum solid, calcareous, usually paucispiral, convex exteriorly 



(Fig. 182, p. 268) Silurian . {i.) Phasianellinae. — Shell 



bulimoid,polished,n(3t nacreous, coloured in patterns, aperture oval. 

 Single genus, rhasiancUa (Fig. 271). (ii.) Turhininae. — Shell very 

 solid, nacreous within, aperture circular or long oval. Principal 

 genera. Turbo, whorls rounded above and below, spines, if present, 

 becoming more prominent with age, operculum smooth or granu- 

 lose, nucleus sub-central ; subg. Ccdlopoma, Ninella, Marmorostoma, 

 Sarmaticus, Prisoyastrr ; Astralium, whorls flattened above and 

 below, spines, if present, becoming less prominent with age, 

 operculum oblong, often excavated at centre, last whorl large, 

 nucleus marginal or sulvmarginal ; subg. ZitJiopoma, Impcrator, 

 Guildfordia, Bohna, Cydocantha, UvaniUa, 

 Cookia, Pomaidax, Pacliypoma. (iii.) Cyclo- 

 nematinae. — Shell nacreous, umbilicate, oper- 

 culum conical outside, whorls scalariform. 

 Principal genera ; Cyclonema, Horiostoma, 

 (?) Amberleya (Silurian to Lias), (iv.) LcjJto- 

 thyrinae. — Shell small, solid, depressed, 

 operculum nearly Hat, nucleus sub-central. 

 Genera ; Lcptothyra, Collonia (?). 



Fam. 7. Neritopsidae. — Tentacles wide 

 apart, long, eyes on short pedvmcles at the 

 outer base; shell solid, neritiform or naticoid, 

 aperture semi-lunar or oval ; operculum 

 (Fig. 183, p. 269) thick, calcareous, non- 

 spiral, exterior face smooth, interior face 

 divided into two unequal parts, with a broad 



median appendage. Devonian . Principal genera : Neri- 



topsis (one recent species), Naticoims (Devonian to Miocene). 



Fig. 271. — PhasianeUa aus- 

 tralis Gmel., Australia. 



