UN 10. 13 



there is a long plate-like tooth which locks into a deeply grooved 

 plate on the left valve ; muscular and pallial scars strongly- 

 defined. 



Inhabits rivers, ponds, and canals in the southern, 

 midland, and some of the northern counties of Eng- 

 land, as well as in some parts of Wales. 



According to Moquin-Tandon, this species breeds 

 during the months of July and August ; the eggs are 

 deposited in masses containing about 100, and a 

 single individual has been known to lay 1500 eggs in 

 two or three days. 



Var. I. radiata. — Shell thinner ; epidermis greenish with 

 yellow rays ; posterior side more compressed above ; hitige line 

 almost straight. River Avon near Bath, Railway lake near 

 Oxford, ^.C Near Birmingham (G. Sherriff Tye), River Went, 

 Yorkshire (Chas. Ashford), near Wakefield (J. Hebden), J,C. 



Var. 2. avails. — Shell triangular-oval, or wedge-shaped, com- 

 pressed and incurved in the middle, rather inequivalve, dark 

 olive-brown ; anterior side broader, abruptly truncate ; lunule 

 broad, deep, oblique. River Avon, Wilts, River Brent, Bath, 

 B.C. 



2. U. PICTO'RUM,* LiNNfi. PL. I. 



Body light red, more or less tinged with grey ; foot reddish or 

 yellowish ; ifiantle edged with brown ; upper orifice elongated, 

 dark brown ; lower orifice grey. 



Shell oblong, compressed, scarcely so solid as U. tumidus^ 

 yellowish girdled with brown in the lines of growth, and green 

 towards the posterior margin, wrinkled transversely ; epidermis 

 thin ; beaks very slightly incurved, not central ; umbonal region 

 less prominent and not so strongly wrinkled as in the last 

 species ; lu7iule long, narrow ; ligament somewhat longer than 

 in U. tumidtis J hinge line straightish ; anterior side rounded ; 

 posterior side sloping gently, rounded at the end ; lower margin 

 nearly straight ; inside cream-colour, or pinkish, pearly ; hinge 



* Painters'. 



