18/9.] '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 petaynce (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. 

 S Crenella decussata, B. C. ii. p. 133, pi. hi. 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 (Cataliua I. 

 and Corea); 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. 

 t/ Dacrydium vitreum, Torell, Spitzb. Moll. p. 138, t. i. f. 2a, 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, 

 ' Cballenger ' Exp. (between the 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 1 876, 

 p. 429. 



This remarkable and pretty mollusk makes a nest (like Modiolaria 

 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. 



