32 MOLLUSCA FROM THE CRAG. 



mediate ray in the aged shell, and fine diverging strife visible between the rays ; ears 

 large, nearly equal, and rayed ; right valve the smaller of the two. 



Lciifflh, 5f . llciyld, b\ inches. 



Locality. Cor. Crag, Ranisholt. 



This noble shell appears not to have lived beyond the Period of the Coralline Crag, 

 at least, I have not seen it from any more recent deposit, although Woodward, in his 

 ' Gcol. of Norf.' has included it in his List of Fossils from the Mamraaliferous Cras: at 

 Tiiorpe, with the letter a at the end of the locality, denoting its abundance, but 

 I have not been able to see a specimen, or ascertain that it was even found in tliat 

 formation, perliaps, fragments or imperfect specimens of P. hlandicus may have been 

 mistaken for it. 



This is the largest species of the genus belonging to the nearly equivalved section, 

 equalling in magnitude the common Scallop. Pecten Magdlanicus somewhat re- 

 sembles this shell, and may be considered its representative on the other side of the 

 Atlantic ; but it has not the rays so distinctly marked or elevated as those upon 

 the Crag shell, and is a flatter or more compressed species, with a few other minor 

 distinctions sufficient to separate the two. 



An American fossil above referred to, as far as can be determined by the figure and 

 description, appears so closely to resemble our shell, that they are here considered as 

 probably the same species ; some slight differences may, however, be pointed out, as 

 our reliance is entirely upon the representation, without the opportunity of comparison. 

 Our shell has the auricles large and unequal, those on the posterior side being much 

 the smaller, while in the American fossil they appear more equal, and somewhat less, 

 and the rays are represented as bifurcating, or double in number, on the outer part of 

 the shell, or its latter growth ; the Crag shell has from 70 to 80 small and convex 

 rays, rounded and slightly imbricated, but never angulated, the distance between them 

 about equal to the rays ; at the outer part of my largest specimen is an intermediate 

 ray, thereby resembling the figure of the American fossil ; between the rays may be 

 seen fine diverging or divaricating strios, crossing the lines of growth in an oblique 

 direction. Under the anterior auricle of the right valve is a large opening. The 

 valves are closed nearly all round, slightly gaping at the shoulders. The same sized 

 rays ornament the auricles, which are also scabrous. Oysters and Barnacles are 

 attached to the roughened surface of t]i(> shell, and may be seen, sometimes upon the 

 right, in others on the left valve. 



This was found, in situ, in the tranquil deposit at Ranisholt. Pecten sublcBviffatiui 

 Ni/st, so much resembles a small specimen in my possession, that it is probably only 

 the young state of this species. 



. Say's name appears to have priority of date, but from the uncertainty of identifi- 

 cation, the much more appropriate one given by Mr. Sowerby lias, for the present, 

 been retained. 



