XI V MONOTOCARDI A — TAENIOGLOSSA 4 1 y 



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

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



Fam. 27. Moclulidae. — 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: Nerinea 

 (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 ovoviviparous. Fresh water. Cretaceous 

 . Principal genera : Melania (with many sec- 

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

 Hemisinus, Pirena, Melanopsis^ Tipliohia^ Paludomus 

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

 kenia (Eocene), Lariua (?). 



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

 tooned, no copulatory organ, otherwise like Melanii- 

 dae; operculum with nucleus sub-marginal. Animal 



oviparous. Freshwater. Cretaceous . Genera 



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

 trema^ Lithasia, Strephohasis)^ Groniobasis, Anculotus, Cevion°^^°' 

 Gyrotoma. 



Fam. 31. Pseudomelaniidae. — Shell resembling that of 

 Melaniidae, but marine. Genera: Pseudomelaiiia^ Loxonema^ 

 Bourguetia^ MacrocMlus. 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: Tuj^ritella^ 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, 



Ooecum. 



VOL. Ill 2E 



Fig. 275.— J/e- 



