106 Mr. W. Clark on the Animals of the Bullidse. 



portion ; its apparent separation certainly puts on the appear- 

 ance of a short distinct subangular foot, sinuated in front. These 

 remarks, I think, explain, if I am not in error, M. Loven's mis- 

 take relative to the foot and tumidity of the mantle. The divi- 

 sion of the foot by the deep groove is doubtless, as in B. hydatis, 

 to increase flexibility, and its under marginal flaps, with the 

 upper ones of the head, miscalled tentacula, are probably to assist 

 both pedal and natatory locomotion. The progression of the 

 present animal is very slow, though otherwise it is sufficiently 

 lively, often turning from one side to the other. The sole of 

 the foot is pale yellow or white, and is often well reflexed on 

 itself at the sides, and sometimes up to the upper disc. The 

 mouth is between the lobes, the fissure is vertical, and furnished 

 with a buccal mass supported by corneous plates and a short 

 spinous tongue. The stomach, as in the typical species, contains 

 a gizzard composed of three minute, elongated, very black, rather 

 pointed plates, flat within, convex without, and all of similar 

 form. The branchial apparatus is a plume of short coarse strands 

 lying in a crypt across the neck. The anus appears to terminate 

 posteriorly, as that portion of the shell is always encrusted with 

 sand, mucus, and fsecal matters. The general aspect of the ani- 

 mal varies from pure white to pale orange-yellow, with occa- 

 sionally a tinge of green. It inhahits the coralline and lami- 

 narian zones. 



This animal has the same leaflets at the sides of the buccal 

 disc, mentioned in B. hydatis, with the groove that is the con- 

 tinuation of the vas deferens, and such of the other organs that 

 could be observed in so minute a species scarcely difier from the 



M. Loven mentions eyes imbedded in the skin ; no appliances 

 enabled us to detect them in this species ; but whether they are 

 there or obsolete, that circumstance is only specific : ex. gr. in 

 Natica monilifera the eyes are obsolete, but in N. Alderi they are 

 easily seen ; the presence or absence of these organs is there- 

 fore not of generic value. All the other points being absolutely 

 similar to the type, we are bound to consider the genus Cylichna 

 as not applicable to B. cylindracea. We have a preparation to 

 show that the linear posterior lobe of the foot lies in the narrow 

 aperture of the shell, agreeably to the invariable characters of the 

 Bulla. 



Bulla truncata, Montagu et auctorum. 



Cylichna truncata, Loven. 



Animal subcylindrical, convolute, flake-white ; mantle hyaline, 

 quite plain, extending occasionally beyond the margins of the 

 shell. The head lobe is large, compressed, very slightly auricled. 



