BULLA. 281 



drudgery of detail, must not forget that M. Cuvier, like 

 Newton and Columbus, pointed out the path, and taught 

 them the 'principia.' 



B. CYLINDBACEA, Pennant et nobis. 



Cylichna cylindracea, Brit. Moll. iii. p. 508, pi. 114. B. f. 6; (animal) 



pi. V. V. f. 3. 



C. mammillata, Brit. Moll. iii. p. 514, pi. 114. C. f. 4, 5. 

 Bulla mammillata, Philippi. 



Animal cylindrical, elongated, convolute ; mantle not thick, 

 rarely produced beyond the front and lateral margins of the 

 shell ; it is edged with a series of minute red papillae ; the 

 linear posterior accessorial lobe of the foot lies within it, and 

 resting on the columella gives the mantle the appearance of 

 being thickened ; the surface of the shell in live and perfect 

 specimens is covered with an olivaceous or orange-brown 

 epidermis. 



It is now necessary to make an extract from M. Loven's 

 generic diagnosis : " Oculi sub eorum basi immersi ; solea 

 brevissima, ovato-quadrata ; pallium limbo incrassato aper- 

 turam postice claudens." If our views of the mantle and 

 foot are correct, it would appear that the linear posterior 

 lobe of the foot has been mistaken for a component part of 

 the mantle, giving that organ the crassitude mentioned by 

 M. Loven. There are no eyes in this species. M. Cuvier 

 ascribes to the genus Bulla four tentacula : what are called 

 the superior pair, are, as we think, the posterior lateral flaps 

 of the head-disc, being the floating margins of the solution of 

 continuity of the disc from the neck ; the inferior pair are the 

 mere roundings of its anterior part, aided by a narrow cir- 

 cumferential groove and a central indentation, that give the 

 aspect of ears ; but neither pair have the similitude or func- 

 tions of the tentacula of the Pectmibranchiata. The flaps 

 occasioned by the deep sinus, at the under part of the foot, 

 are quite as produced as the superior pair of M. Cuvier, and 

 may as well be called tentacula ; it is surely a misnomer to 

 call these appendages by that term in any of the Bullidce ; 

 their only use seems to be that of fins or paddles to assist in 



