294 FOSSIL SHELLS OF THE CRAG. 



the finest lace-work. The shell is rather flat, and regularly 

 oval ; the central areas finely and granularly striated ; on the 

 lateral and terminal areas, the radiating ridges are so regu- 

 larly intercepted by concentric lines, as to present a cancel- 

 lated appearance. The margin is apparently smooth, but the 

 lens discovers very minute sandy granulations ; its colour is 

 brown, banded with darker patches. The general colour of 

 the shell is creamy- white, variegated with red. 



Chiton atratus. (Con. lUus. fig. 57, 58). 



Ch. testa ovali-oblonga, laevi, sul)carinata ; valvis sutrectis, subrostratis; 

 areis lateralibus inconspicuis ; margine laevi. Long. 1 ; lat. i, poll. 



Falkland Islands. Mus. Miller. 



The smooth, narrow, slightly angulated species above de- 

 scribed, is of a blackish brown colour ; the lateral areas are 

 not distinctly marked, except by rays of lighter colour in 

 some specimens on them, and on the terminal valves. The 

 margin is smooth. 



May, 1840. 



Art. Yl.—On the Fossil Shells of the Crag. By S. V. Wood, 

 Esq., F.G.S. 



( Continued from page 234.^ 

 a. Inequilateral^ ligamental pit at the angle ; edge crenulated. 



Nucula nucleus, Fleming. PI. xiv. fig. 1. 

 Area nucleus^ Linn. Syst. 



Red crag, Sutton. Coralline crag, Sutton. 



This shell is not common in the red crag, although very 

 abundant in the coralline deposit. It exhibits a well marked 

 identity with the British variety of Lamarck's Nucula mar- 

 garitacea ; and though this species appears to have existed 

 fi-om the commencement of the tertiary period, the specimens 

 from the Paris basin, as well as those from the London clay, 

 are much larger than those of the crag ; a condition perhaps 

 depending upon the reduction in temperature which the cli- 

 mate of this part of the globe is supposed to have undergone, 

 since the eocene strata were deposited. 



