XIV MONOTOCARDIA — TAENIOGLOSS A 4 1 1 



Sub-order II. Monotocardia. — Heart with one auricle, one 

 ctenidium (the left), monopectinate, fused with the mantle 

 (except in Valvata)^ one kidney, not receiving the genital 

 products, nervous system somewhat concentrated, proboscis and 

 penis usually present. 



{a) Ptenoglossa. — ^Radula with formula 00.0.00, teeth 

 similar throughout, outermost largest (p. 224). 



Fam. 1. lanthmidae. — Snout prominent, blunt, no eyes, shell 

 helicoid, fragile, bluish, no operculum; eggs carried on a raft of 

 vesicles attached to the foot (Fig. 42, p. 126). Pelagic only. 

 Pliocene . Genera : lanthina^ Recluzia. 



Fam. 2. Scalariidae. — Shell long, turriculate, whorls often 

 partly uncoiled, with longitudinal ribs and prominent lamellae, 

 aperture circular, operculum spiral, corneous, animal carnivorous. 



Ordovician . Principal genera : Scalaria^ Eglisia^ Elas- 



moneura (Silurian), Holopella (Silurian to Trias), Aclis. 



(6) Taenioglossa. — Radula with normal formula 2.1.1.1.2, 

 marginals sometimes multiplied (p. 223). 



Section I. Platypoda. — Foot more or less flattened ven- 

 trally. 



Fam. 1. Natieidae. — Foot very large, produced before and 

 behind, propodium reflected upon the head, eyes absent or buried 

 in the integument, central and lateral tooth of the radula tri- 

 cuspid, middle cusp strong ; shell globular or auriform, outer lip 

 simple, operculum corneous or calcareous, nucleus excentrical. 



Carboniferous . Principal genera : Natica^ with many 



sub-genera ; Ampullina (Tertiary) ; Amaura ; Deshayesia (Ter- 

 tiary) ; Sigaretus (Fig. 91, p. 186), shell auriform, last whorl very 

 large, operculum much too small for the aperture. 



Fam. 2. Lamellariidae. — Mantle reflected over more or less 

 of the shell, shell delicate, no operculum. Eocene . Prin- 

 cipal genera: Lamellaria^ shell completely internal, transparent; 

 auriform ; some species deposit their eggs on compound Ascidians 

 (p. 74) ; Velutina, shell almost entirely external, paucispiral, 

 with a thick periostracum ; Marsenina^ shell auriform, partly 

 internal; Onchidiopsis, shell a membranous plate, internal. 



Fam. 3. Trichotropidae. — Branchial siphon short, eyes on 

 the outer side of the tentacles ; radula closely allied to that of 

 Velutina; shell conical, last whorl rather large, periostracum 

 thick and hairy, operculum blunt claw-shaped, nucleus terminal. 

 Cretaceous . Genera: Trichotropis^ Torellia. 



