458 BULLID.E. 



shaped, lying at the base between the two lateral plates ; each 

 plate has two small holes (muscular impressions?) in the 

 middle : odontopJiore, rhachis wanting ; uncini 12-15, arranged 

 in a single row, claw-shaped, and furnished on the inner side 

 with a jagged crest. 



Shell squarish oval, depressed in front, ver^' thin and fra- 

 gile, semitransparent, glossy, and iridescent : sculpture, plait- 

 like and irregular Lines of growth, and a few extremely slight 

 and more irregular spiral lines, which latter are not discern- 

 ible except with a lens and at certain angles of light ; the 

 texture, examined under a microscope, resembles curdled milk : 

 colour whitish, with sometimes two or three clear streaks across 

 the back : spire very loosely coiled, with the nucleus extremely 

 SDiall and concealed by a shelly deposit from the hinder lobe 

 of the mantle ; it is always more or less indented, and in the 

 young is slightly umbilicate : mouth roundish -oval, of enor- 

 mous size compared with that of the convoluted portion, and 

 occupying seven-eighths of the under sui'face ; it is obliquely 

 truncated above, and rounded below : outer lip dilated, with 

 a sinuous and very thin edge ; the upper part slopes outwards, 

 and projects considerably beyond the spire ; inner corner re- 

 ceding and acute-angled : inner Up spread over the pillar, and 

 forming at the angle where it meets the outer lip a thick and 

 shapeless callus : pillar sharp and flexuous ; there is no um- 

 bilical groove or depression. L. 0-85. B. 0-7. 



\q.j:. patula. Smaller, with the mouth larger and more 

 expanded. 



Habitat : Sand^ from low-water mark of spring tides 

 to 50 f.; on all our coasts between the Firth of Forth 

 (Forbes) and Jersey (Dodd). It seems to attain its 

 largest dimensions in the Bristol Channel ; specimens 

 which I found in Swansea Bay are nearly an inch and 

 a quarter in length. The variety is from Tenby, Dub- 

 lin Bay, and Connemara. I am not aware that this 

 species has occurred in a fossil state except at Belfast, 

 where Mr. Grainger observed it. Its existing distri- 

 bution comprises the Atlantic sea-board from Upper 

 Norway to the Canaries, the Mediterranean, Adriatic, 

 and iEgean, at depths varying from 4 to 110 f.; speci- 



