XIV MONOTOCARDIA — -TAENIOGLOSSA 417 



CeritJiidea, Lampania, all brackish water), Diastoma (Eocene), 

 Cerithiopsis ; CcriteUa (Jurassic), Bracliytrema (Jurassic), and 

 Planaxis (subg., Quoyia and Holcostoma). 



Fam. 2 7. Modulidae. — No siphon, radula of Cerithium ; shell 

 with short spire, columella strongly toothed at the base, aperture 

 nearly circvilar. Eecent. Single genus, Modtdvs. 



Faim. 28. Nerincidae. — Shell solid, long sub-cylindrical, aper- 

 ture channelled, columella and interior of whorls with continuous 

 ridges, extending up the spire. Genera : Nerinea (Trias to 

 Cretaceous), A])tyxiella (Jurassic). 



Fam. 29. Melaniidae. — Border of mantle festooned, foot broad, 

 with an anterior groove, penis present ; radula closely resembling 

 that of Cerithium ; shell long, spiral, with a thick periostracum, 

 surface with tubercles, ribs, or striae, suture shallow ; operculum 

 corneous, paucispiral, nucleus excentrical. Animal 



ovoviviparous. Fresh water. Cretaceous . 



Principal genera : Mdania (with many sections or 

 sub-genera), Pachychilus, Claviger ( = Vibex), Hemi- 

 sinvs, Pirena, Melanopsis, Tiphohia, Paludomus 

 (subg., Philopotamis, Tanalia, Stomatodon), Hant- 

 kenia (Eocene), Larina (?). 



Fam. 30. Pleuroceridae. — Mantle edge not 

 festooned, no copulatory organ, otherwise like 

 Melaniidae ; operculum with nucleus sub-marginal. 



Animal oviparous. Fresh water. Cretaceous . yic. 275.— Me- 



Genera: Pleurocera (including lo, Fig. 12, p. 16, l^"^^"- <^on- 

 Angitrema, Lithasia, Strejjhohasis), Goniohasis, Ancit- Ceyion. 

 lotus, Gyrotoma. 



Fam. 31. PseudoTiielaniidae. — Shell resembling that of 

 Melaniidae, but marine. Genera : Pseudomelania, Loxonema, 

 Bourguctla, Macrochihis. Palaeozoic to Tertiary strata. 



Fam. 32. Turritellidae. — Mantle with a siphonal fold on the 

 right side; radula variable (p. 224); shell long, whorls many, 

 slowly increasing in size, tranversely ribbed or striated, aper- 

 ture small ; operculum corneous, nucleus central. J urassic . 



Principal genera : Turritdla, Mesalia, Protoma, Mathilda (?). 



Fam. 33. Coecidae. — Tentacles long, eyes sessile at their base : 

 shell small, spiral in the young form, spire generally lost in the 

 adult, the shell becoming simply a straight or curved cylinder ; oper- 

 culum corneous, multispiral. Eocene . Single genus, Coecum. 



VOL. Ill 2 E 



