OF MOLLUSCA. 57 



C. Gymnoglossa. Teeth none. Tentacula folded (p. 54, 56). 

 Fam. XXIV. PYRAMIDELLID^E. 



Shell turrited; nucleus and apical whorls reversed, transverse. 

 Mouth moderate ; pillar-lip plaited. Operculum horny, spiral, of few 

 whorls, with a thin flap on the inner side. Tentacula broad, folded. 

 Eyes sessile, on the outer side of the base of the tentacles. Foot 

 moderate. Mantle enclosed. Teeth none or rudimentary. 



a. Shell free ; pillar-lip plaited. Operculum spiral. 



1. Obeliscus. 



Shell turrited, spiral ; cavity marked with internal varices ; mouth 

 ovate ; outer lip often toothed ; pillar with three or four oblique 

 plaits in front. Operculum half-ovate, subspiral, with a notch. — 

 Adams, Gen. Moll. t. 24. f. 5 a. 



1. O. maculatus, t. 123. f. 13. 



2. O. ventricosus, t. 123. f. 10, 12. 



2. Pyramidella. 



Shell turrited. Operculum narrow. — Adams, Gen. Moll, t, 24. 

 f. 4 b, c. 

 1. P. auris-catti, Adams, Gen. Moll. t. 24. f. 4. 



3. Odostomia. 



Shell turrited ; mouth ovate ; pillar lip with a single oblique plait 

 in front. 



1. O. spiralis, t. 125. f. 4 ("not correct," Alder), t. 128 a. f . 3 ; 



Forbes fy Hanley, B. M. t. F.F. f. 8, 9. 



2. O. interrupta, t. 128 a. f. 4. 



3. O.clavula, t. 128 a. f. 2. 



The animal of Odostomia spiralis is white, and has the tentacles 

 ear-shaped or longitudinally folded, with the eyes at the internal base. 

 Characters as in the genus Chemnitzia. The figure given in the 

 Annals of Nat. Hist. xiii. t. 8. f. 13, is deficient in not displaying 

 this character ; from the minuteness and transparency of the animal, 

 the folds of the tentacles can only be seen in a favourable light. — 

 Alder, Cat. Moll. N. 52, 1848. 



Animal of Odostomia strong, depressed. Head broad. Tenta- 

 cles ear- shaped, externally channeled in front ; hinder lamella more 

 or less produced on the nape ; front one thin, often connate, with the 

 opposite one before the eyes. Eyes large, immersed without bearer 

 between the base of the tentacles. Proboscis retractile under the 

 base of the tentacles when evolved, broader than the nape, as long or 

 longer than the foot, round, attenuated at the end. Mouth minute, 

 edentulous 1 Chin elevated, separate from the foot, broader above. 



