LEPTON. 97 



(Thompson) ; Inner and Outer Hebrides (Barlee) ; Ork- 

 neys (Thomas) ; Aberdeenshire (Macgillivray). " On each 

 side the coast of Ireland. Found among Mytili growing 

 on the rocks at the Skerries off Portrush, and about the 

 roots of Alga growing between tide-marks, Belfast Bay 

 and coast of Clare " (W. Thompson). 



It appears to be generally distributed through the North 

 and South Atlantic, ranging into the Mediterranean. The 

 Kellla rubra of North America, judging from the ex- 

 pression of Gould (Invert. Massachuss. p. 60, f. 38), seems 

 to differ from this species, although, perchance, as that 

 admirable describer observes, not essentially so. The 

 hinge of Mediterranean examples, received from Dr. Phil- 

 lippi, is much more developed, and the teeth longer and 

 more manifest than in our British shells. 



LEPTON. Turton. 



Shell equivalve, suborbicular, subequilateral, compressed, 

 surface shagreened or smooth, gaping slightly at the sides; 

 beaks acute ; margin plain. Hinge composed of a pair of 

 teeth-like lamina on each side of a triangular central 

 excision in one valve ; a primary apical tooth in front of a 

 subtriangular excision of the hinge-margin, and flanked on 

 each side by a sublateral lamina on the other. Pallial 

 impression simple. 



Animal compressed, mantle freely open in front, its 

 margin extending considerably beyond the shell, and 

 bearing superiorly a fringe of filaments, one of which is 

 much larger than the rest. A short siphonal tube, with 

 single aperture at the larger end of the shell. Foot thick 

 and tapering, keeled and disked, furnished with a byssal 

 groove. Branchial leaflets two on each side, and separate. 



VOL. II. o 



