46 



Valvata cristata (The Crested Valve Shell). Muller. 

 Figures 22, 23, and 24. 



22. 



23. 



2.4. 



This minute shell was first described by Boys, in the 

 year 1784, in *' Walker's Minute Shells'* 



Valvata cristala varies in fits form, chiefly in the 

 looseness of its coil, and in the upper side of the shell; 

 this is mostly flat, but occasionally it is rather convex. 

 In some specimens sent to me by Mr. Jeffreys, of Swan- 

 sea, they are decidedly convex, whilst in others, ob- 

 tained from the Bulwell bogs, they are slightly concave. 

 The general form of the shell is discoidal, flat above, 

 having the spire rather sunken, and possessing a deep 

 and large umbilicus, in which all the whorls are seen. 

 It is fragile, semi-transparent, shining, and has three 

 whorls. The diameter of this shell averages about a 

 tenth of aa inch. 



It is frequently covered with a black incrustation. 



The Crested Falve shell is an inhabitant of ditches, 

 canals, ponds, and lakes, mostly on aquatic vegetation. 



The localities in this neighbourhood are — the bogs 

 at Bulwell, where it is abundant ; the river Leen at 

 Bulwell, although not plentiful; an almost stagnant 

 brook near the Trent, between Beeston and Atten- 

 borougb, where it is rare; tolerably abundant in a 



