CONCIIYLIX—DITHYRA. 23. 71 



being so much proJuced at one end : but they gradually run into 

 each other, and may be readily known from all the species of this 

 division, by the regular transverse striaj, which grow gradually 

 fainter and disappear towards the iiinge. 



Mactra tesld ohlongd depressd incequilatcrali, latere produclo 

 rotunda to altera sublruncato, vmttonibus incurvis. 



Shell oblong flattish inequilateral, rounded at the elongated 

 side and somewhat truncate at the other, with the beaks in- 

 curved. 



Tab. nost. 5, fig. 8. 



Mus. nost. Dredged up in the offing of Exmoutli. 



Shell five-eighths of an inch long, and an incli and a quarter 

 broad, opake and strong ; one side elongated, sloping from the 

 beaks^ and rounded ; the other shorter and somewhat angular, 

 where it is a little open: color dull greyish-white, covered with 

 a shining bronzed skin reflecting metallic lustres ; coarsely and 

 irregularly striate transversely, with a few coarser ridges towards 

 the hinge: inside glossy greyish-white, with the margin plain : 

 beaks rather prominent and pointed, a little inclining to the 

 longer side. 



Of this very beautiful shell we know neither description nor 

 figure, in the outline it something resembles the Mactra deal- 

 bata described in the eighth vol. of the Linnean Transactions, 

 p. 68, tab. 1, fig. 10, and the Dorset Catalogue, tab. 7, fig. 7. 

 But that shell is represented as thin and transparent, and some- 

 what angular at the longer side : the teeth also appear to be 

 different. 



(leaunita. 

 5. 



