43 



The Lake Mud Shell is the largest fresh-watev 

 univalve of Great Britain. The form of the shell is an 

 oblong-oval, the body whorl being very large and broad, 

 and the spire acute. Mouth very capacious, and outer 

 lip spreading. Strong columellar fold. Suture deep. Very 

 thin and fragile for so large a shell. Horn-coloured. 



The animal is yellowish-olive. 



The usual size is 1^ inches long by an inch wide. 



Specimens forwarded by the Rev. C. Lowndes from a 

 still sheet of water in Dr. Lee's beautiful park at Hart- 

 well, Buckinghamshire, are larger than I have seen from 

 any other locality, the average length being nearly two 

 inches by an inch and a line broad. The largest ex- 

 amples near Nottingham measure If inches by 10 lines. 



There are several varieties: — 



Var. FRAGiLis of Moutagu is more slender and not 

 so broad. It is not uncommon in this neighbourhood. 



Var. rosed labiatum of Sturm is thicker and has a 

 purple throat. 



An abundant and widely spread species, which is 

 mostly found in stagnant water overgrown with water 

 plants ; occasionally met with in canals, brooks, and 

 slow rivers. 



Described by Merret, in his " Pinax," in the year ) 667. 



It is said to attain a very large size in the S.E. of 

 Germany. In the Danube specimens are found four 

 times as large as those procured in England. 



Deposits from 100 to 130 eggs at a time. They are 

 oval, and are marked with a yellow spot. 



In this neighbourhood it is found at Stanton-on-the- 

 Wolds in a small isolated pool ; Beeston Ryelands in 

 the River Trent, rare; in the Old Trent at Sawley, 

 brooks at Lentou, and rare at Radford Grove. 



Other localities are— Kent and Dorset (Montagu), 

 Sussex (Paget), Essex (Sheppard), Norwich (Bridg- 



