232 136 



towards the anterior end. The dorsal margin descends abruptly on both sides, in 

 front in an almost straight line, and at the back somewhat convexly. The ventral 

 side is decidedly curving. The surface is covered with close-set, fine, concentric ribs, 

 all of which do not, however, pass entirely round the valve, but are most of them 

 incomplete and inserted irregularly between each other. Upon the anterior and 

 posterior sides these ribs are crossed by fine radiating grooves which make the 

 surface granulated at these places; these radiating grooves are at different distances 

 apart and are most evident at the anterior end. At the upper part of the middle 

 of the valves, somewhat below the beaks, at the point where the valves are most 

 convex, the concentric ribs disappear and a bare glossy spot is formed. The lunule 

 is large and lanceolate, circumscribed by a distinct impressed line, not affected by 

 the radiating sculpture, but merely striated by fine lines of growth; a well-defined 

 area does not occur. The interior of the shells is smooth, white and glossy. In 

 the right valve there are three cardinal teeth of which the central is triangular; 

 the anterior is small, and from it proceeds a lamellar tooth which is situated 

 between the lateral tooth and the upper margin which is double. In the left valve 

 there are also three cardinal teeth; the posterior is the smallest, it is compressed, 

 narrow and acute. Each valve has an anterior lateral tooth, oblong, compressed 

 and triangular, parallel with the upper margin and separated from it by a deep 

 groove. The inner ventral margin is flat. 



Long. 4 mm., alt. 4 mm., crass. 2-5 mm. 



Between Koh Rin and Clifl" Rock, 15 fathoms (■■/a). Gulf of Rayong, 7 — 10 

 fathoms, sand and mud (^/s). Koh Chuen, 30 fathoms (^/a). W. of Koh Chuen, 

 mud mixed with clay (^/s). S. of Koh Chuen, 30 fathoms, shells ('''/a). S. of Koh 

 Samit, 20 fathoms, mud (2 -f "'/a). South-east of Koh Samit, 13—14 fathoms, mud 

 mixed with sand ('/a). S. of Koh Tulu, 10 fathoms, mud mixed with sand (^/a). 

 Sound of Koh Chang, 3—5 fathoms, soft clay (^/a). W. of Koh Chang, 20 fathoms, 

 mud (3 + i-'/a). Between Koh Kut and Koh Kahdat, 10 fathoms, shells (2 + ^^-hi). 

 Between Koh Kahdat and Koh Kut, 6 fathoms, mud mixed with clay (^**/2). S. of 

 Koh Kahdat, 8-10 fathoms, mud ('■'/a). W. of Koh Kut, 15 fathoms, mud ('^'a). 

 S. of Koh Kut, 17—20 fathoms, mud (^/a). 



This characteristic and beautiful little species is common in the Gulf of Siam; 

 it is nearest related to C. nana, Melv., and C. aniica, Smith, from which it is, 

 however, easily distinguished. I have ventured to dedicate this species to Mr. James 

 Cosmo Melvill, who, by his valuable papers, has contributed so largely to our 

 knowledge of the marine Molluscan fauna of Asia. 



Circe (Lioconcha) picta, Lam. 



Cylherea picta, Lamarck, Hist. nat. d. anira. sans vert., V, 1818, p. 5öi), No. 33. — od. 2, VI, 1835, p. 309, 



No. 33. 

 Lioconcha picla, Lamarck, Römer, Malakozoolog. Blätter, IX, 1862, p. 144, No. 13. 

 Circe — — Reeve, Conchol. icon., XIV, Circe, Sp. 42. 



Cylherea (Lioconcha) picta, Lamarck, Römer, Monogr. d. Molluskengatt. Venus, I, p. 104, No. 15, pi. 45, fig. 3. 

 Meretrix — — — Anthony, Bull, du Museum d'Hist. Nat. I'aris, 1905, p. 494. 



