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. cyLINDRACEA, Pennant et nobis. 
Cylichna cylindracea, Brit. Moll. ii. p. 508, pl. 114. B. f.6; (animal) 
PleaVe Vedio. 
C. mammillata, Brit. Moll. iii. p. 514, pl. 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 papille; the 
linear posterior accessorial lobe of the foot les 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. Lovén’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 Bul/a 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 Pectinibranchiata. 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 Bullide ; 
their only use seems to be that of fins or paddles to assist in 
