340 Mr. Clark on some species 



Animal entirely white, foot very large. The body behind is 

 divided into two or three digitations. Length ^th inch. Breadth 

 •j^gth inch. 



^AeZ/subglobose, subopake, of a dead frosted white colour, deli- 

 cately reticulated, appearing covered with fine gauze ; the circum- 

 ference of the posterior or upper part is somewhat constricted, as 

 if a thread had been tightly tied around it. The columellar mar- 

 gin is arcuated, a little reflected, and in the middle of it is a 

 flexure or notch ; apex rather rounded and slightly umbilicated. 

 Length -^^th inch. Breadth, more than ^'^tii inch. 



Six of these beautiful Bidlcece were dredged alive off Budleigh 

 Salterton, Devon, in August 1827, and I believe belong to an en- 

 tirely new species. This I have named pridnosa, in consequence of 

 its frosted snowy colour. At the first view of the shell I thought it 

 might prove to be either the long lost Bulla denticulata, or B. 

 emarginata of Adams, (Linn. Trans. 5th vol.) ; but on comparing 

 it with that gentleman's description and figures, I find it distinct. 

 This species is rather more rolled up than any of its congeners ; it 

 resembles much in shape a young Bulla Ilydatis^ and seems to be 

 the connecting link of the Bullcece with the BuUa\ The foot 

 appears very large when not reflected on the back of the animal, 

 and the hind margin of the body is more digitated than in either 

 of the last species. Tlie animal flaps the sides of the foot upwards 

 and downwards, as if beating the water, with considerable quick- 

 ness, especially when first taken from the sea. No gizzard could 

 be detected after the most careful examination with a good lens. 

 This appears to be a rare species, and only occasionally to be pro- 

 cured by deep dredging seven or eight miles from the shore. 

 Some individuals are marked with a more or less wide, chesnut 

 coloured, transverse band. Perhaps it may be said, that two genera 

 ought to be formed of the preceding species, in consequence of 

 one of them being provided with a testaceous gizzard, and the 

 others not having any testaceous appendages. I am not of this 

 opinion, as it cannot be doubted but that all have a gizzard, though 

 in some it is only of a coriaceous or skinny nature : if this distinction 

 was admitted, dissection alone could distinguish the animals, as 

 the external appearances are the same iu those furnished with tes- 



