296 THE VOYAGE OF H.M.S. CHALLENGER. 



Pecten noronhensis, n. sp. (PI. XXI. figs. 4-46). 



Testa paulo inEequivalvis, couvexa, inaBquilateralis, alba, aurantio vel .saturato-rosco 

 maculata, costis ad 17 valde promineutibus instructa ; cost^e valvae dextrge iuterstitii.s 

 profundis pulcberrime transversim lamellatis latiores, laevigatse ; valva sinistra costis 

 paulo gracilioribus, interstitia sequantibus, lira mediana teiiui Ijipartitis instrur-ta, undique 

 et supra et inter costas tenuissime lamellata. Auriculae insequales, radiatim tenuiter 

 costulatro. Pagina interna imrpuraseens, alljo limbata, vel omnino alba. 



This species is somewhat inequivalve, the right valve being a trifle deeper than the 

 left. It is rather convex, and inequilateral, and has an apparent obliquity, owing to the 

 hinder slope from the umboues being longer than the anterior. It is white, and more 

 or less copiously blotched with orange or deep rose. The valves are differently sculptured. 

 The right has the ribs (about seventeen in number) smooth above, and broader than the 

 deep intervening sulci, which are most beautifully ornamented with close and excessively 

 delicate concentric lamellae. In the left valve the ribs about equal the furrows in width, 

 are divided into two parts by a fine central lira, and are crossed by the very delicate lamellae 

 which also occur in the sulci. The ears are unequal. In the left valve both are concave 

 at the sides, especially the front one, which is the smaller. In the right valve the posterior 

 is incurved laterally, and the anterior is deeply cut in underneath and ornamented with 

 about five squamate ridges. The interior of the largest specimens is purple, with the 

 exception of a narrow white border, but smaller specimens are entirely colourless within. 



Length 27 mm., height 26, diameter 12. 



Habitat. — Station 113a, off Fernando Noronha, in 25 fathoms; volcanic sand and 

 gravel. 



This species is considerably like Pecten gibbus, Linn., but may be recognised l)y the 

 following difi"erences. Judging from the few specimens at hand, it appears to be rather 

 more convex, more inequilateral, the ribs are stouter, fewer, more elevated and sharply 

 cut, and differently sculptured, and the posterior auricles are less oblique at the side and 

 more concave. 



Pecten 2yhiH2)pii, Recluz. 



Peden pJiilipjjii, Eecluz, Joiirn. de Conch., 1854, vol. iv. p. 52, pi. ii. figs. 15, IG. 

 Pecten philip2ni, Petit. Cat. Moll. Test. Europe, pp. 79, 200. 

 Peden pliiliiipn, Hidalgo, Moluscos Marin. Espaua, pi. xxxii. tig. 2. 

 Peden philippii, Weiukaiiff, Conchyl. Mittelm., vol. i. pp. 251, 300. 

 Peden commutatm, Monterosato, Poche Note Conch. Medit., 1875, p. G. 



Habitat. — Station 75, off the Azores, in 450 fathoms; volcanic mud. 



