GO'i^CEYLlA—DITHYRA. 38. 169 



the other, white covered with an olive-brown skin, with numerous 

 nearly equidistant flat longitudinal ridges which are covered with a 

 fine brown downy pile : beaks nearer one end, rather close together ; 

 inside glossy with pale rays. 



** Margine interno integerrimo. 5, 6. 

 With the inner margin very entire. 



Arca testa oblongd decussatd barbatd, latere antico angulato, margine perforans. 



suhhiante. 

 Shell oblong decussate and bearded, angular at the anterior end, and 

 slightly open at the margin. 



Tab. nost. 13, fig. 2, 3. 

 Arca perforans. Turton, Conch Diet. p. 9. 

 Arca lactea. Pennant^ iv. p. 216, tab. 61, fig. 2. 



Da Costa, p. 171, tab. II, fig. 5. 

 Montagu, Test. Brit.p. 138. 

 Donovan, British Shells, iv. tab. 135. 

 Linn. Trans, viii. p. 92. 

 Turton, British Fauna, p. 160. 

 Dorset Catal. p. 36, tab. 11, fig. 5. 

 Dillwyn, Descript. Catal. p. 236. ' 

 Pectunculus exiguus. Lister, Conch, tab. 235, fig. 69. 

 Mus. nost. Wedged in the interstices of rocks on the western 

 coasts, and sometimes inclosed in the interior of stones. 



Shell three quarters of an inch long, and rather more in breadth, 

 convex and sloping to the margin, angular on the anterior side, white 

 covered with A fine downy skin which fringes the margin: beaks 



