42 



met with this variety in the River Trent, at Newstead 

 Abbey, and in the beautiful lake at Elvaston Hall. 



LimnaBus pereger frequently leaves the water to crawl 

 upon the moist mud in the immediate neighbourhood. 



The shells are often covered with a calcareous deposit. 

 . This species generally copulates in August. Sixty to 

 eighty eggs are deposited at one time. 



First described by Dr. Lister, in 1678. 



I have frequently examined the eggs of this species 

 microscopically, and have never failed to observe the 

 head and tentacles perfect in the youngest specimens. 

 The action of the heart is very plainly visible. 



In hot weather this mud shell is found in great num- 

 bers, basking on the surface of the water. 



Found in Ireland (Thompson), Scotland (Forbes), 

 Isle of Man (Forbes), Scilly Isles (Millett), Germany 

 (Pfeifler), Sweden (Nilson), France (Draparnaud), I. of 

 Corsica (Payradeau). 



Found fossil in the fresh water deposits near London 

 (Morris). 



LiMN^os STAGNALis [The Lake Mud Shell]. Linnceus, 

 Fisrure 105. 



