94 SYSTEMATIC ARRANGEMENT 



Jaws distinct. Tongue linear. Tentacles compressed, short, diver- 

 ging. Eyes large, black, with a peculiar, very visible, prominent 

 white pupil on the outer side of the hinder part of the base of the 

 tentacles. Foot very short, rounded. Operculigerous lobe simple. 

 Operculum horny, ovate, of few whorls. Walks with its foot, its 

 dilated lips forming an intermediate loop. 



1. Truncatella. 

 Character of the Family. 



1. T. truncatula, t. 123. f. 14, t. 125. f. 14 ; Forbes fy Hanley, 



B. M. t. F.F. f. 10. 



2. T. littorina, t. 125. f. 6. 



3. T. atomus, t. 125. f. 15. 



4. T. littorea, Forbes fy Hanley, B. M. t. M.M. f. 3. 



Teeth of Truncatella Montagui 3 • 1 ■ 3 ; the central rather nar- 

 row, with a recurved central tooth ; lateral inner broad ; inner upper 

 edge with three broad denticles ; central rather like inner, but nar- 

 rower and more oblique ; outer conical, compressed, curved ; apex 

 denticulated beneath. 



The mantle of Truncatella Montagui is plain ; rostrum annular, 

 long, very broad, flat, nicked at the end, and auricled on each side. 

 Jaws white. Branchial plume single, elongated, kidney-shaped. 

 Tentacles short, flat, subtriangular. Eyes black, large, pupils white, 

 on middle of tentacles. Foot thick, oval, very little extended. — 

 Clark, 383. 



The eyes of Truncatella littorea white, with dilatable white pupils 

 as in T. Montagui, near the tip of the broad, short tentacles. Foot 

 thick, elongated, oval, and looped in its walk. 



" Tentacula perbrevia ad latera ciyiitis dispositis divergentia, ocu- 

 los in latere superiore neque exteriore gerentia, caput in proboscidem 

 bilobam, tentaculis longiorem productum. Pes admodum brevis, 

 ellipticus, utrinque rotundatus, ex observatione cl. Lowe (Zool. 

 Journ. v.) quam transcripsit Desh. (Ed. 2. Lamk. viii. 363) sulco 

 mediano transverso divisus, quod ipse non vidi, sed erroneum puta- 

 verim, cum animal prorepens sicut Paludincs parvse, capite molem 

 corporis falciatur." — Philippi, Sicil. ii. 133. 



2. Tonichia. 



Proboscis nicked. Tentacles blunt. Foot short, ovate, lobed on 

 each side in front. Shell elongate, perforated, truncate ; periostraca 

 olive ; mouth elliptical, oval. Peristome double or triple, conti- 

 nuous ; left lip expanded, rather reflexed, slightly nicked. Opercu- 

 lum horny, ovate, subspiral. 



1. T. ventricosa, Benson, Ann. fy Mag. Nat. Hist. 1851, 378. 



