286 BULLION. 



** Testaceous shield concealed within the mantle. 



BULL^A, Lamarck et Auct. et nobis. 



PHILINE, Loven. 



This section of the Bullidce 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. iii. p. 539, pi. 114. E. f. 1; (animal) 

 pi. U.U. f. 1. 



Animal throughout pale yellowish-white, and densely pow- 

 dered with very minute, intensely white, distinct opake points ; 

 its shape, when in 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 being conspi- 

 cuously quadrilobated. Above, when on the march, the ani- 

 mal is gently convex below, flat or slightly 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 continued 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 



