FOSSIL SHELLS OF THE CRAG. 295 



h. Ligamental pit at the angle^ edge entire. 

 Nucula trigonula, Nob. PI. xiv. fig. 3. 



Shell ovato-deltoidal, tumid, smooth, umbo prominent, margin crenulated ; 

 lunule embedded, convex in the middle. Longitudinal diameter, i§ ; 

 transverse diameter, \ of an inch. 



Coralline crag, Sutton. 



Posterior side truncate and straight, the centre of the lu- 

 nule only projecting beyond a line drawn from the umbo to 

 the extremity of the ventral margin ; anterior side angulated ; 

 from six to eight teeth on one side of the ligamental pit, and 

 from twelve to fifteen on the other, with a sub-carinated dor- 

 sal projection; no vestige of longitudinal st^^ice externally, 

 except when the outer coating is removed. This shell differs 

 from Nucula trigona, ' Min. Con.' tab. 192, fig. 5, in being 

 more tumid, — in the posterior side being more truncated, and in 

 the umbo terminating in an acute angle. Fifty specimens of 

 this fossil in my possession preserve such uniformity of cha- 

 racter as to warrant its estabhshment as a distinct species. 



Nucula tenera, Nob. PI. xiv. fig. 2. 



Shell subtriangular, smooth, margin entire. Longitudinal diameter, f ; 

 transverse diameter, ^ an inch. 



Mammaliferous crag. South wold. Red crag, Bawdsey. 



Bawdsey, a village on the Suffolk coast, is the only red 

 crag locality from which I have obtained this shell: it closely 

 resembles Nucula nucleus in shape, but it is destitute of lon- 

 gitudinal stricB, and has the margin entire. Area tenuis, 

 Montague, 'Test. Brit.' Suppl. page ^Q, tab. 29, fi^. I, ap- 

 proaches this fossil in most of its characters, differing only in 

 having the dorsal margin more rounded, and in having but 

 fifteen teeth, the crag species possessing upwards of twenty ; 

 six or seven on one side of the ligamental pit and fourteen 

 or fifteen on the other. Many of the specimens from the 

 crag appear as if they had been concentrically striated, but 

 this arises from their altered state, two or three in my posses- 

 sion being quite smooth. This shell appears to connect the 

 two species above referred to, having the contour of the former 

 with the entire margin and delicacy of the latter. 



Nucula Cobboldics, 'Min. Con.' tab. 180, fig. 2. 

 Mammaliferous crag, Bramerton. Red crag, Sutton. 



The red crag specimens, jlidging from those which T have 



