14 UNIONIDjE. 



moderately strong ; teeth as in last species, but sharper and 

 not so strong ; 7nuscular scars well defined ; pallial scars in- 

 distinct. 



Inhabits rivers, canals, and ponds in England as far 

 north as Yorkshire. It may be distinguished from 

 U. tumidiLS by its oblong shape and thinner shell, by 

 the straightness of the upper and lower margins, as 

 well as by its beaks being less tumid, and its hinge 

 and teeth more slender. The eggs of this species are 

 laid during the months of May, June, and July ; 

 Bouchard-Chantereaux says that a single individual 

 will, during that time, produce the enormous number 

 of 220,000. The name of pictortun (belonging to 

 painters) was given to this species because in former 

 times the Dutch painters made use of the shells for 

 holding their colours, and in this country at the present 

 day they are sold containing gold and silver leaf for 

 illuminating. 



The pearls produced by this and the last species 

 are small and valueless. 



Var. I. radiafa. — Shell having faint and narrow rays of 

 green, which diverge from the beak. River Avon, Bath, B.C. 



Var. 2. curvirostris. — Shell smaller, shorter, and flatter ; 

 epiderinis yellowish-green with brown zones ; posterior side 

 curved and wedge-shaped. In a brook near Harpsden Wood, 

 Henley-on-Thames (Rich). 



Var. 3. latior. — Shell broader and shorter, yellowish-brown. 

 Canal near Oxford, B.C. Near Birmingham (G. Sherriff Tye), 

 J.C. In a brook near Harpsden Wood, Henley-on-Thames 

 (Rich). 



Var. 4. compressa. — Shell very broad and flat, upper margin 

 raised and curved ; posterior side greatly compressed and 

 attenuated, assuming a beak-like form, and having a double 

 ridge and furrow which runs from the beak in the younger 



