LEPTON. 195 



compressed and almost flat, thin, semitransparent and glossy : 

 sculpture, numerous and minute circular pit-marks, which are 

 caused by the intersection of a close network of fine longi- 

 tudinal and transverse ribs, the former radiating from the beaks 

 and curved towards the back and sides ; there are also distinct 

 lines of growth, which vary in their distance from each other : 

 colour snow-white : epidermis exceedingly thin, and only 

 shown by an iridescent hue in young specimens : marc/ins ob- 

 liquely truncate on both sides, with the angles rounded, some- 

 what incurved in front, and slightly curved outwards at the 

 back : beaks small, somewhat prominent, placed a little nearer 

 to the anterior than to the posterior side : hinge-line gently 

 curved, occupying nearly one-third of the circumference of the 

 shell : cartilage triangular, yellowish-brown, close to the beaks 

 on the posterior side : hinge-plate broad, incurved, excavated 

 in the middle for the reception of the cartilage : teeth, one 

 small and slight but upright cardinal, lying directly under the 

 beak and close to the cartilage, and a long laminar lateral on 

 each side of the cavity containing the cartilage ; the lateral 

 teeth are placed at a little distance within the hinge -line : in- 

 side iridescent, striated lengthwise but irregularly; margin 

 plain : pallial and muscular scars usually indistinct, owing to 

 the thin texture of the shell. L. 0-575. B. 0-45. 



HABITAT : Shelly gravel and sand, in 8-20 fathoms, 

 on the coasts of Cornwall, Devon, and Dorset, as well as 

 at Guernsey, and in the south and west of Ireland. It 

 is recorded in the ' British Mollusca ' as having been 

 found by Lyons and Hanley at Tenby, by M 'Andrew at 

 Anglesea, and by Barlee at Oban ; but another locality 

 there given on my authority (" off Skye ") must have 

 originated in a mistake. Searles Wood found a single 

 specimen in the Coralline Crag at Sutton. Its foreign 

 range appears to be limited or little noticed. Lillje- 

 borg has taken it at Christiansund in Norway, Malm 

 and Loven on the coast of Bohuslan in Sweden (the 

 former in 12-20 fathoms), I found it at Etretat in Nor- 

 mandy, Cailliaud in the Departement of Loire-inferieure, 

 and M f Andrew dredged it at 8 fathoms in Vigo Bay. 

 It may be decidedly considered a local species. 



K2 



