OF NORTHUMBERLAND AND DURHAM. 93 



In slow streams, rather rare. Mill Race, Jesmond Dean. Near 

 Stockton. — Mr. Hogg. 



Family. Kelliad^e, Forbes. 

 105. LEPTON, Tarton. 

 1. L. CONVEXUM, n. s. 



Shell rather convex, transversely ovate, white ; covered with 

 minute transversely oblong punctures ; hinge with the central 

 tooth rather large, and the lateral laminae small. 



A single valve of a minute shell with these characters has oc- 

 curred to us at Cullercoats. It is evidently a Lejiton, and differs 

 from L. squamosum in being rather more convex, in having the 

 punctures of the surface oblong instead of circular, and in the 

 greater proportional size of the tooth. These seem to indicate a 

 specific distinction, but as the specimen is scarcely a line in dia- 

 meter, and probably young, we cannot speak very confidently. 

 The nucleus on the umbo is, however, so much smaller than that 

 of L. squamosum, that we conclude it never attains the same size. 



106. KELLIA, Turton. 



1. K. SUBORBICULARIS, Moilt. 



Mya sulorliculark, Mont. Test. Brit. 39, t. 'l^, f. 6. 



At the roots of Laminaria digitata, and other sea-weeds, un- 

 der stones, and in the cavities of stones and old shells ; not 

 rare. 



This species is subject to great variety of size -and form ; so 

 much so, that we have thought more than one species might be 

 confounded under the name, but we have failed to obtain any 

 distinguishing character that can be depended upon as per- 

 manent. Two varieties may be mentioned ; the one thin, 

 transparent, and with a delicate play of iridescent colours on 

 the surface. This is generally found at the roots of tangle. The 

 other, which is more common among rocks between tide- 

 marks, is smaller, more orbicular, more strongly striated, and 

 covered with an ochreous crust near the umbones. Intermediate 

 forms occur. 



The animal ofKellia is very remarkable, and constitutes a new 



