ASSIMINIA. 71 



rather acute. The sutural line is simple, but distinct, 

 and scarcely at all slanting. The aperture is rather small, 

 occupies about three-eighths of the total length of tlie shell, 

 and rather more than half the basal diameter ; its shape 

 is ovate-acute, the posterior end being a little contracted. 

 The edge of the outer lip, which is continuously arched, 

 and rather prominent, is a little flattened anteriorly. 

 There is no umbilicus, but only a slight indentation be- 

 hind the pillar-lip, which latter is somewhat expanded, 

 appressed, rather short, curved, yet not so much as the 

 outer one, and is spread into a callosity posteriorly. A 

 line and three quarters for the breadth, and not quite 

 three lines for the length, may be regarded as the average 

 dimensions of full-sized individuals ; the breadth is often- 

 times, however, rather more in proportion. 



The animal was carefully examined by the Rev. M. J. 

 Berkeley, and described and figured by him in the fifth 

 volume of the " Zoological Journal." The muzzle is 

 deeply notched in front, fuscous, strongly annulated, and 

 has pale edges to its lip ; on each side is a groove running 

 backwards from the base of the tentacula. These organs 

 are very short, obtuse, and fuscous, and bear the eyes 

 on their tips. The foot is broadly obovate, obtuse, above 

 fuscous, beneath olivaceous, shaded with cinereous ; its 

 front margin is double. 



It inhabits brackish water "amongst Conferva^ Ruppia, 

 Zanichellia, &c.," in the estuaries of rivers in the south- 

 east of Enofland. Greenwich marshes. 



