CO^CHYUX—DITHYRA. 39. 171 



The beaks appear to separate and become gradually more dis- 

 tant at their points, as they advance in age, exhibiting the 

 marks of their annotination, or annual growth, by transverse 

 lines or wrinkles in the hollow space between them, and not 

 on the external surface, as in most other bivalves. 



Pectunculus testd obliqud iiKsquilaterali, nntice stihangulatd. Giycymeiis, 

 Shell oblique and inequilateral, a little angular at the anterior 

 side. 



Tab.nost. 12, fig. 1. 

 Area Glycymeris. Linn. Syst. Nat. p. IIJ3. 



Gmelin,Syst. p. 331S. 



Turton, Linn. Syst. iv. p. 256. 



Pennant, Brit. Zool. iv. p. 216. 



JAnn. Trans, viii. p. 93, tab. 3, fig. 3. 



Turton, British Fauna, p. J 60. 



Dillwyn, Descript. Catal. p. 241. 



Turton, Conch. Diet. p. 7. 



Ckemnits, vii. p. 229, tib. 57, fig. 564. 

 Pectunculus maximus. Lister, Conch, tab. 240, fig, 77. 

 Mns. nost. Western coasts and British Ciiannel. 



Shell growing to more than three inches in diameter, rather 

 convex, but not so tumid as tlie Pectunculus pilosus, very finely 

 decussate, and when fresh clothed round the margin witli a dark 

 Drown silky skin, under which it is greyish-white with obscure 

 longitudinal reddish marks: the outline is oblique, with a slight 

 angularity at the produced side. 



z 2 



