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Show 18/9.] « LIGHTNING '/ND ' PORCUPINE ' EXPEDITIONS. 561 17. PECTEN FRAGILIS, Jeffreys. (Plate XLV. fig. 1.) P. fragilis, Jeffr. in Ann. & Mag. N. H . Nov. 1876, p. 424. ' Porcupine ' Exp. • 1869, St. 23a (young, but perfect and living) : 1870, Atl. 16, 17 (fragments). Distribution. 'Valorous' Exp.; 1450-1750 fms. Norwegian Arctic Exp. 1876-8; 656-1333 fms. According to Friele there are no ocelli in the edge of the mantle. 18. PECTEN VITREUS, Chemnitz. Pallium vitreum, Chemn. Conch.-Cab. vii. p. 335, t. 67. f. 637a. Pecten vitreus, B. C. v. p. 168, pi. xcix. f. 6. 'Lightning' Exp.: St. 6, 7. ' Porcupine ' Exp. 1869 : St. 3, 4, 5, 6, 13, 23, 23a, 47. 1870 : Atl. 1, 2, 3, 6, 8, 9, Vigo B., 16,17a, off C. Espichel, 24, 26,27, 28, 28a, 31-34. Some specimens from the same locality are more or less covered with tubercles or short scales on the concentric lines of growth; others are quite smooth and constitute the variety abyssorum. The microscopic striae which radiate from the beak are also sometimes nearly wanting in young specimens. Distribution, Greenland, Iceland, Scandinavia, Shetland, S.W. France, coast of Portugal, Mediterranean, N.E. America, var. abyssorum ' Challenger ' Exp. (W. Patagonia) ; 20-600 fms. Herr Friele dredged a specimen at Bergen attached to Primnoa, which measured an inch in length and breadth. Fossil. Pliocene and Post-tertiary. Norway, Sicily. 1. AMUSSIUM FENESTRATUM, Forbes. Pecten fenestratus, Forh. Rep. Brit. Assoc. 1843, pp. 146, 192. P. philippii, Acton, Ricerche conchiliologiche, 1855, f. la. P. actoni, v. Martens, Mai. Bl. 1857, p. 194, t. iii. f. 1-3. 'Porcupine' Exp. 1870: Atl. St. 24, 27, 28, 28a, 36; Med. Cartagena B., Adventure Bank, off Rinaldo's Chair. Var. cancellata. White and of thinner texture, with the concentric ridges less numerous than the longitudinal striae, which are equal in size; it is also destitute of the inside ribs. 'Porcupine' Exp. 1869, St. 37, from the great depth of 2435 fathoms ; a living specimen. A remarkable monstrosity occurred in an upper valve from the Adventure Bank having the proper sculpture of the lower valve, viz. being concentrically and closely striated ; and the upper valve of another specimen has partly its own decussated sculpture and partly that of the lower valve. The sculpture is very variable, and is more or less deficient as well on the outside as in the inside of both valves ; and the ears of the lower valve are nearly equal in two specimens. Distribution. Coast of Portugal, Mediterranean, and iEgean; 50-250 fms. Fossil. Pliocene. Sicily and Rhodes. P. ineequisculptus, Tiberi. P. concentricus of Forbes is the lower valve of either this species or A. hoskynsi. In neither of these species is the shell " sequivalvis," as described by him ; nor did he notice the PROC. ZOOL. Soc-1879, No. XXXVI. 36 |