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Show 1879.] 'LIGHTNING'AND 'PORCUPINE'EXPEDITIONS. 569 Distribution. Brittany, G. Gascony, N. Spain, Provence, Canaries; 12-50 fms. Fossil. Pliocene. Siena, Palermo. Modiola gibberula of Cailliaud, and Lithodomus semigranatus of Reeve. Differs from Modiolaria petagnce (with which it has been found) in size, shape, sculpture, and the prolongation of the terminal beard-like epidermis. CRENELLA DECUSSATA, Montagu. Mytilus decussatus, Mont. Test. Brit. Suppl. p. 69. Crenella decussata, B. C. ii. p. 133, pi. iii. f. 4 ; v. p. 172, pi. xxviii. f. 6. ' Lightning ' Exp. : St. 4, 5. 'Porcupine' Exp. 1870: Med. Adventure Bank. Valves, smaller than North-Atlantic specimens. Distribution. Spitzbergen to the coasts of Northumberland and co. Antrim, Novaya Zemblia, White Sea, and coasts of Russian Lapland, Davis Strait to New England, N. Pacific (Catalina I. andCorea); 0-1750 fms. Fossil. Pliocene and Post-tertiary. Norway, Scotland, Sicily; 0-40 ft. DACRYDIUM VITREUM (Holboll), Moller. Modiolal vitrea (Holboll), Moll. Ind. Moll. Grcenl. p. 19. Dacrydium vitreum, Torell, Spitzb. Moll. p. 138, t. i. f. 2 a, b. ' Porcupine ' Exp. 1869 : St. 23, 23 a, 25, 37, 38, 65. 1870 : Atl. 16, 17, 17a, 22, 30. Distribution. Swedish arctic Exp. 1868, ' Valorous' Exp. 1875, Novaya Zemblia, Norwegian arctic Exp. 1877 and 1878, 'Challenger' Exp. (between tbe Azores and Bermuda), Norway from Vadsoe to Christianiafiord, both sides of the Mediterranean, Gulf of St. Lawrence, New England ; 30-2750 fms. Fossil. Pliocene and Post-tertiary. Elie in Fifeshire, Cassel, Palermo. Modiola pygmcea of Philippi and Dacrydium hyalinum of Monte-rosato. I cannot discover any difference except size to distinguish Mediterranean from North-Atlantic specimnns. As to the name and characteristics of the genus Dacrydium, I would refer to the 'Annals and Magazine of Natural History ' for November 1876, p. 429. This remarkable and pretty mollusk makes a nest (like 3Iodiolaria discors and Lima hians) consisting of a narrow tubular case twice the length of the shell. The case is lined with a delicate membrane, and coated with minute Foramiuifera, fragments of sponge, and coc-cospheres, which are firmly agglutinated. The Dacrydium inhabits the broader and lower half of the case, its front or " ventral" margin lying in the direction of the narrower part or opening. |