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 lOO, and a 

 single individual has been known to lay 1500 eggs in 

 two or three days. 



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

 yellow rays ; posterior side more compressed above ; hinge line 

 almost straight. River Avon near Bath, Railway lake near 

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

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



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

 pressed and incurved in the middle, rather inequi valve, 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 ; mantle 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 ; epiderinis 

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

 less prominent and not so strongly wrinkled as in the last 

 species ; lunule long, narrow ; ligament somewhat longer than 

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

 posterior side sloping gently, rounded at the end ; lower margi7i 

 nearly straight ; i7iside cream-colour, or pinkish, pearly ; hinge 



* Painters'. 



