540 BULLIDiE. 



open and tlilated as to display tlie structure even to the 

 apex, whilst the proportion of the ventral area occupied by 

 the body, which is oblique and narrow on that side of the 

 shell, is extremely small. The general shape is rounded 

 subquadrate, a little narrowed above, and rather expanded 

 and rounded below. The transparent surface is of an 

 uniform lustrous snow-white hue, and is merely marked 

 with the wrinkles of increase, which latter, however, are 

 often very conspicuous. The crown is devoid of spire, and 

 is a little indented. The outer lip is not regularly arcu- 

 ated, but is much sinuatcd in its course ; it is slightly 

 produced above the crown (without forming an angle) 

 posteriorly, where it advances ; is most prominent rather 

 below the middle ; and recedes obliquely anteriorly. Large 

 individuals attain to an inch and an eighth in length, and 

 seven- eighths of an inch in breadth. 



The animal is massive and white, slimy and slug-like. 

 Seen from above it appears as if formed of four lobes, a 

 capital disk, a mantle investing the shell, and two lateral 

 lobes ; these latter are, however, the involute wing-like 

 processes or margins of the foot. The capital disk is ir- 

 regularly pentagonal and slightly emarginate in front. The 

 margin of the mantle posteriorly is very slightly laciniated. 

 The membranes of the tongue are each furnished with a 

 single series of claw-shaped lateral teeth. Loven has 

 observed the embryo ; he found it to be furnished with a 

 spiral shell, provided with an operculum, and to be ca[)able 

 of swimming by means of a ciliated veil. He also found 

 the egg-capsules ; they are gelatinous, hydrophanous, 

 ovate, and contain very numerous eggs arranged in single 

 file, on a very long funiculus, folded in a loose spiral. 



This animal iidiabits probably all parts of the British 

 seas, but is capricious in its appearance, and seems on the 



