XIV MONOTOCARDIA — TAENIOGLOSSA 417 



(Eocene), CeritMopsis ; Ceritella (Jurassic), Brachytrema 

 (Jurassic), and Planaxis (subg., Quoyia and Holcostoma). 



Fam. 27. Modulidae. — No siphon, radula of Cerithium; shell 

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

 nearly circular. Recent. Single genus. Modulus. 



Fam. 28. Nerineidae. — Shell solid, long, sub-cylindrical, 

 aperture channelled, columella and interior of whorls with 

 continuous ridges, extending up the spire. Genera: Nermea 

 (Trias to Cretaceous), Aptyxiella (Jurassic). 



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

 broad, with an anterior groove, penis present; radula closely re- 

 sembling that of Cerithium; shell long, spiral, with a thick peri- 

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

 operculum corneous, paucispiral, nucleus excentrical. 

 Animal ovo viviparous. Fresh water. Cretaceous 

 . Principal genera : Melania (with many sec- 

 tions or sub-genera), Pachychilus^ Claviger ( = Vihex)^ 

 Hemisinus^ Pirena^ Melanopsis^ Tiphohia^ Paludomus 

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

 kenia (Eocene), Lariyia (?). 



Fam. 30. Pleuroceridae. — Mantle edge not fes- 

 tooned, no copulatory organ, otherwise like Melanii- 

 dae; operculum with nucleus sub-marginal. Animal 



oviparous. Freshwater. Cretaceous . Genera: p^^ 



Pleurocera (including Zo, Fig. 12, p. 16, Angi- lania con- 

 trema, Lithasia^ Strephohasis'), Groniobasis, Anculotus, c^t^on^^^^' 

 G-yrotoma. 



Fam. 31. Pseudomelaniidae. — Shell resembling that of 

 Melaniidae, but marine. Genera: Pseudomelania^ Loxonema^ 

 Bourguetia, Macroehilus. 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, transversely ribbed or striated, aper- 

 ture small ; operculum corneous, nucleus central. Jurassic . 



Principal genera: Turritella, 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; 



operculum corneous, multispiral. Eocene . Single genus, 



Coecum. 



VOL. Ill 2E 



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