BIVALVIA. 31 



in the Sicilian Beds, I have not yet seen it from any of the three Crag Formations of 

 Essex, Suffolk or Norfolk. As it is a fossil in the Clyde Beds, and may, probably, be 

 hereafter found in the Crag, it ought not to be here passed over in silence. The 

 specimen figured (which is the right valve) was given to me by James Smith, Esq., 

 of Jordan Hill, and is undoubtedly identical with the British shell recently obtained in 

 considerable plenty by Mr. George Barlee. 



Our specimen contains a good deal of animal matter, with some slight remains of 

 colour, as indicative of its comparatively modern origin. The shell like that of 

 P. fifferimis, is ornamented with curved radiating or diverging striae, but less promir 

 nent and distinct, and most visible at the lateral edges. A specimen of P. Biimasii, 

 given to me by Professor Edward Forbes, which he obtained from a great depth in the 

 Mge&n Sea, does not appear to differ specifically from the British shell, and I have 

 followed his example in uniting the two. Our fossil, however, appears to agree with 

 the recent British specimens better than with the Dumasii from the Mediterranean, in 

 having a rather larger posterior auricle ; but my specimen from the iEgean differs also 

 in that character from the Mediterranean shells, in having as large an auricle com- 

 paratively as the British specimens. The number of ribs is a variable character; 

 sometimes the right valve has six, when the left one has only five, the depressions of the 

 one valve corresponding to the elevations of the other, and vice versa. 



In this, as in most of the species of this genus, the auricles are comparatively 

 larger in the younger shell than in the adult ; my specimen, is a full grown shell, with 

 six ribs or elevations, and the whole surface rayed or striated longitudinally, made 

 rough or scabrous by elevated lines of growth, and the diverging or curved striae 

 visible only at the sides.* 



7. Pecten Princeps, /. Sowerbi/, Tab. VI, fig. I. 



Pecten Princeps. J. Sow. Min. Conch., t. 542, fig. 2, 1826. 



— — 77oo(/wa?YZ. Geol. of Norf., p. 4-1, 1833. 



— — 5. JFood. Catalogue, 1840. 



— — Morris. Cat. of Brit. Foss., p. 115, 1843. 



— Cltntonius? Say. Jouni. Acad. Nat. Sci., vol. iv, p. 135, pi. ix, fig. 2, 1824. 



— — ? Conrad. Foss. of the Med. Tert. of the United States, p. 47, pi. 23, 



fig. 1, 1838. 



— sDBL^viGATUS ? juv. Nyst. Coq. Foss. de Beige, p. 298, pi. 24, fig. 4, 1844. 



Spec. Char. Testa, orbiculari, subhuequivalvi, convexd, lontjitudinaliter cosiatd, costis 

 numerosis confertis, suhsquaviosis, interstitiis divaricatim striatis ; auriculis magnis sub- 

 aqualibns ; valrd dextrd minori. 



Shell orbicular, slightly inequivalve, convex, externally ornamented with numerous 

 close set, rounded and slightly squamose or imbricated striae, with a small inter- 



* A specimen much worn, and -without its auricles, very recently found iu the Red Crag, is in my 

 Cabinet, and may possibly be of this species, but it is too much mutilated for fair examination. 



