130 



Planorbis marginatds [The Margined Coil Shell]. 



Drapamaud. 



Figure 93. 



Described by Lister, in 1678. 



Very similar iu general appearance to Planorbis 

 carinatus, but not so much compressed, semi-trans- 

 parent, and unpolished. Wrinkled; carinated ; colour 

 brownish, but mostly enveloped in a black coating 

 Lower disc flat, upper disc concave. There are five 

 well separated convolutions. In Planorbis carinatus 

 the body whorl is very large in comparison with the 

 preceding whorl ; there is not so great a diflFerence in 

 ^his respect in Planorbis marginatus. Aperture quad- 

 rant shaped. 



Specimens five-eighths of an inch in diameter are 

 considered large. In this neighbourhood examples 

 have been dredged measuring as much as eight lines 

 and a half in diameter. 



Animal, black. 



Var. rhomheus. The keel is considerably less, the 

 gyrations closer, the lower disc very hollow in the 

 centre, and the upper disc less concave. 



Var. Draparnaldi, Keel more central. Smaller. 



An abundant species, amongst water plants in stag- 

 nant poorls and slow rivers. 



Lays six eggs at one time (Chautereaux). 



