BIVALVIA. 



117 



Sj)ec. Char. Testa minutd, ovata, subinmquilaterali, compressd, tenui, fragili ; dente 

 cardinali unico ; dentihus later alibus magnis, distantibus. 



Shell small, ovate, nearly equilateral, compressed, very thin, and fragile ; hinge 

 with one cardinal tooth, and two large and distant lateral teeth. 



Length, |-th of an inch. 



Locality. Cor. Crag, Sutton. Recent, British Seas. 



When compiling my Catalogue, one specimen of a shell strongly resembling the 

 description given by Turton as a distinct species of Lepton, was in my Cabinet, and 

 I am sorry to say it is the only one I have as yet seen. As the authors of the ' Hist, 

 of British Mollusca ' confirm its existence in the recent state, and have given a good 

 distinguishable figure, I am able with a little more confidence to describe my shell 

 under the name originally given. My solitary specimen possesses characters more in 

 accordance with the diagnosis of Lepton than of Kellia, as given by the proposer of 

 the two Genera, both as regards the hinge as well as the shell. My specimen is, I 

 suppose, the left valve having the cardinal tooth before the ligament, which is placed 

 in a triangular fossette immediately within a slightly prominent umbo, two large 

 lateral teeth extend to the edge of the dorsal area, and the two sides are a little 

 unequal in size, the anterior being a trifle the larger, and the less rounded ; the shell 

 appears to have been very thin, and the impression of the muscles indistinct, while 

 the exterior is somewhat rough and uneven, as if it had been altered by erosion. 



Kellia,* Turton, 1822. 



Amphidesma (sp.). Lam., 1818. 

 Lasea. Leach, MS., 1819. Brown, 1827. 

 Eeycina (sp.). Besh., 1824. 

 Petricola (sp.). Gray, 1835. 

 Tellimya (sp.). Brown, 1827. 

 Cyladina. Cantraine, 1830. 



BoENiA. Phil., 1836. 

 Aligena. H. C. Lea, 1843. 

 ScACCHiA (sp.). Phil., 1844. 

 Myalina? Conrad, 1845. 

 PoKONiA. Becluc, 1846. 

 Chironia. Desk., sec. Gray. 



Generic Character. Shell generally small and thin, equivalved, subequilateral, 

 orbicular, spheroidal, ovate, or roundedly-oblong ; tumid, or compressed ; surface 

 smooth, or covered with visible lines of growth. Hinge composed of two, sometimes 

 only one, tooth in each valve, with a trigonal pit for the reception of the ligament, 

 which is within the margin of the shell, though visible in some species when the 

 valves are closed. Impressions by the adductor muscles suborbicular, often indistinct, 

 that by the mantle without a sinus. 



Animal of the form of the shell, with the edges of the mantle disconnected 

 only in places, extending posteriorly into one short siphonal tube, and at the anterior 



* Etym. Name commemorative of J. M. Kelly, Esq. 



