300 OSTREAD^. 



Pecten subrufws, Turt. Dithyra Brit. p. 210, pi. 17, f. 1. — Brit. Marine Concli. 



p. 116. — SowERBY, Thesaur. Conch, vol. i. p. 53, pi. 19, f. 



208, 209, 210. 

 „ Audonmii, Payraudeau, Cat. Moll. Corse, p. 77, pi. 2, f. 8, 9. — Hanl. 



Recent Shells, vol. i. p. 273. 

 Peiijne ojxrculaire, Chenu, Traite Element, p. 101, f. 339. 

 Pecten pleheius and Pecten sukatus (fossil), Sowerby, Min. Conch, pi. 393. 



Both valves of this orhicular shell are convex, but the 

 lower one is decidedly the more so. They are tolerably 

 strong, and similar in sculpture to each other, being every- 

 where rough with minute scales or squamular crense, 

 which are most crowdedly arranged on very numerous and 

 closely disposed elevated radiating striulse. From eighteen 

 to twenty- three ribs diverge from the umbo of each valve ; 

 these are but moderately elevated, and in the more typical 

 examples rounded, and of about the same width as their 

 interstices. In the variety Audouinii, the scales are espe- 

 cially developed, and those which, crowning the summit 

 of each rib, are seated on stria so coarse as almost to 

 carinate it, are manifestly larger than the rest. The ribs 

 of the immature specimens are abrupt, and narrower in 

 proportion than in the adult : their interstices are simply 

 sculptured with very delicate concentric lamellae. The 

 auricles are of very nearly equal dimensions, and rather 

 small than otherwise ; they are subrectangular above, the 

 under ones inclining slightly to the obtuse, the front one 

 of the upper valve to the acute : occasionally they are 

 costellated and echinated, but chiefly on the under valve, 

 more frequently they merely exhibit coarse and minutely 

 squamular elevated striae. The auricular sinus is small and 

 shallow, delicately pectinated, or rather, minutely dentated 

 (at times obscurely) below, with the terminal angulation 

 smgle and acute. The hinge-margin is not level, but rises 

 a little on either side of the beaks, particularly in the less 



