PLECTROrilORUS. 1-5 



Genus TESTACELLA, Cuvicr. 



Mantle divided into numerous lobes, usually concealed 

 by the shell, but capable of being drawn forward over the 

 body. 



Shell external, auriform, depressed, sub-spiral, situated at 

 the hinder extremity of the back. 



Si/ /i. Testaccllus, Faure-Biguet. 



Ex. T. Maugei, Ferussac, pi. 72, fig. 7. Shell, 

 T. Maugei, fig. 7, a. 



The shell, which appears affixed to the tail, on account of 

 the posterior position of the respiratory cavity, is ear- 

 shaped, and covered with a thin epidermis ; the apex is very 

 small and spiral, the aperture is very large and oblong, the 

 outer lip is entire, the inner lip is thickened and involute, 

 and the muscular impression is oblong-lunate. 



Species of Testacella. 



haliotoidea, Drap. Maugei, Firm. 



Lartetii, Dupuy. scutulum, Sow. 



Genus PLECTROPHORUS, Bosc. 



Mantle shield-like, at the anterior part of the body ; 

 orifice of respiratory sac at the right anterior border. Body 

 with a small, external, prominent, testaceous appendage, 

 situated towards the posterior extremity. 



Ex. P. corninus, Bosc, pi. 72, fig. 8. Shell, P. corni- 

 nus, fig. 8, a. 



Plectrophorus is at once recognised by the remarkable 

 horny shell placed on the hind portion of the foot ; three 



VOL. II. s 



