OF MOLLTJSCA. 



139 



Fig. 75. — Operculum 

 of Catillus. 



4. Catillus. 



Shell half-ovate or oblong; apex small, subposterior ; inner lip 

 small, arched ; aperture very large. Operculum small, rudimentary 

 (fig. 7b). 

 1. C. porcellanus, t. 46. f. 5, 6, 12, 34. 



" Mantle of Catillus very broad and very ex- 

 tensible, like the Pat el Ice ; between the foot and 

 the mantle is a keel where the gills are in the 

 Patellce. When kept in a vessel of water they 

 come to the surface to respire. The operculum is 

 placed on a large membrane resembling a mantle." 

 — Van Hasselt, Bull. Sci. Nat. iii. 86. 



Central teeth of Catillus moderately broad ; second large, trans 



Fig. 76. — Teeth of Catillus, from Ceylon. 



verse ; third and fourth very small, conical, rudimentary ; fifth 

 oblong, with a transverse, toothed crest ; lateral teeth numerous, 

 hair-like (fig. 76). 



B. Sides of the foot with a continuous fringe, with three or four 

 elongated tentacles on its upper surface, often continued, and 

 forming one or two lappets on the forehead between the ten- 

 tacles. Shell generally pearly within. The central teeth small, 

 subequal in size, often rather different inform. 



* Rostrum not produced. Proboscis ? retractile, surrounded by an 

 expanded veil. 



Fam. II. ROTELLADiE. 



Mouth small, rounded, sunken at the base of the veil. Proboscis 

 short, cylindrical, retractile. Tongue-membrane linear-elongate. 

 Teeth like Trochus. Tentacles linear ; right free, simple, with a 

 compressed lobe on its inner side ; left tentacles with a large mem- 

 branaceous expansion folded over the mouth and then back to the 

 left side of the head, and continued by a slight ridge to the lateral 

 fringe. Lateral fringe distinct, with three tentacles on each side, 

 produced on the front of the right side into a large, oblong, fleshy 

 lobe, which probably covers the base of the shell, and forms the 

 callosity over the axis (see Ann. $• Mag. N. H. 1853, xii. 179). 



