286 BULLIDA. 
** Testaceous shield concealed within the mantle. 
BULL/AA, Lamarck et Auct. et nobis. 
Putting, Loven. 
This section of the Bullide is represented by the B. aperta. 
As it is an influential type, we have given a full description 
of the animal. 
B. aperta, Linn., Auct. et nobis. 
Philine aperta, Brit. Moll. wi. p. 539, pl. 114. E. f. 1; (animal) 
pba Wecf al 
Animal throughout pale yellowish-white, and densely pow- 
dered with very minute, intensely white, distinct opake points ; 
its shape, when im action, is subrotund or a, broad oval, in 
which state it has the indistinct aspect of four lobes, but 
when quiescent, by the reflexion of the lateral parts of the 
pedal disk, the upper range has the figure of bemg conspi- 
cuously quadrilobated. Above, when on the march, the ani- 
mal is gently convex—below, flat or shghtly concave. The 
upper lobe, which may be considered the head, as the mouth 
is at its extremity, is somewhat elongated, rounded in front, 
truncate behind, without eyes or tentacular flaps, and at about 
half the length of the animal is broken in upon by a deep 
transverse groove; it is then contimued to the posterior ex- 
tremity by a thin membrane springing from the furrow of the 
fissure which envelopes the shell that covers the viscera, and 
forms the posterior portion of the upper area; this membrane 
is not strictly a lobe, but merely an envelope to keep the 
anterior part of the shell in position, the apex being imbedded 
in the terminal membrane ;—M. Cuvier says, unattached by 
a muscle, which perhaps is doubtful, as I shall show. 
The pedal disk, at the same point as the upper, is also deeply 
transversely grooved, and, like it, there arises an appendix or 
continuation membrane which secures the anterior under part 
of the shell; these upper and under posterior membranes are 
open at the extremity on the right side for the development of 
several of the posterior organs, but the tissues coalesce on the 
left, and the free parts have a subtruncate aspect with their 
