TKOCHTJS. 305 



It appears, if there be no error, an unaccountable condition, 

 that all pectinibranchous animals having spiral circular oper- 

 cula should be hermaphrodites, whilst those of the same 

 respiratory structure, with opercula of every other shape, 

 should be bisexuals. It would be a loss of time to attempt to 

 explain what is inexplicable ; we refer to, and must rest on, 

 the anatomical details at the conclusion of the descriptive 

 notes. 



* Conical, and not umbilicated. 

 TROCHUS, Linnaeus. 



T. GRANULATUS, Bom. 



T. granulotus, Brit. Moll. ii. p. 499, pi. 67. f. 7, and pi. 68. f. 3 ; (ani- 

 mal) pi. D.D. f. 4. 



Animal inhabiting a conical spiral shell of white or pink 

 colour, furnished with close-set circular moniliform striae. 

 Mantle plain and even with the aperture. The head is a 

 long, thick, smooth elongated muzzle, yellowish-white, marked 

 with fine longitudinal pale red-brown lines and points, and at 

 an eighth of an inch from the termination clothed with an 

 excessively close-set, very fine white fringe, that falls over the 

 anterior part of the head like hair, which is scarcely visible 

 without being floated, giving the buccal disk the appearance 

 of being deeply sunken ; it is striated with brown lines, verti- 

 cally cloven, and contains a pair of oval greenish-white horny 

 laminae, supported by fleshy plates, between which the very 

 short lingual riband passes to the oesophagus. The tentacula 

 are long, tapering, pointed, rather flat, and marked above with 

 a longitudinal central brown line, yellow beneath ; the eyes 

 are on short distinct external offsets, the cornea being dark 

 blue with a black pupil. The head-lobes are very small, 

 lateral, close to the inner angles of the tentacula, and are 

 mere partially-cloven white fillets ; the neck-lappets form two 

 large, pendent, sinuated, slightly scalloped, yellowish-white 

 membranes, of similar figure, not differing as in some species. 

 The foot is very large, extending beyond each end of the shell, 

 anteriorly subtruncate, dilated at the external angles, and 

 tapering to a lanceolate posterior extremity, which is marked 



