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Show 1879.] 'LIGHTNING' A N D 'PORCUPINE' EXPEDITIONS. 577 The teeth are much more numerous and finer than in L. pustulosa. Yoldia nana of M . Sars. 9. LEDA TENUIS, Philippi. Nucula tenuis, Phil. En. Moll. Sic. i. p. 65, t. v. f. 9. L. pygmcea, B. C. ii. p. 154 ; v. p. 173, pi. xxix. f. 5. 'Lightning' Exp.: St. 2, 3, 5, 7. 'Porcupine' Exp., 1869: St. 1,8, 13, 14, 15, 17, 18, 23a, 35,61, 62, Loch Torridon. 1870 : Atl. 1, 2, 3a, 9, 13, 22, 24, off C. Sagres, 26-34 ; Med. 45, Cartagena B., 55, Benzert Road, Adventure Bank, off Rinaldo's Chair. Distribution. Scandinavia to the iEgean ; 10-650 fms. Fossil. Pliocene and Post-tertiary. Siberia?, Scandinavia, Great Britain and Ireland, Belgium ?, Transylvania ?, Biot, Italy ; 0-240 ft. This species was referred by Philippi in his second volume to the Nucula pygmcea of Von Miinster; but the description and figure of the latter species given by Goldfuss in his ' Petrefacta Germaniae/ and specimens of the fossils kindly sent me by Dr. Wiecbmann, have convinced me that they are different species. I have therefore adopted Philippi's original name tenuis. The well-known Nucula tenuis of Montagu belongs to another genus ; but Philippi did not distinguish the genus Leda, and therefore changed his name for that of Von Miinster. According to Forbes, N. gibbosa of James Smith is a variety of the present species. L. tenuis does not appear to inhabit the Arctic seas, although L. lenticula of Moller, = Yoldia abyssicola, Torell, has been mistaken for it by some authors, which makes it difficult to verify all the localities mentioned by them. 10. LEDA LENTICULA, Moller. Nucula lenticula, Moll. Ind. Moll. Grcenl. p. 17. Yoldia abyssicola, Torell, Spitz. Moll. t. i. f. 4, a, b. 'Porcupine' Exp. 1869 : St. 9, 23a, Loch Torridon (perfect but dead and perhaps semifossil, like L. arctica). 1870 : Atl. 34, 27, 28, 30. Valves only. Distribution. Wellington Channel, Davis Strait, Dutch arctic Exp., Novaya Zemblia, Norwegian arctic Exp. 1878, Shetland (semi-fossil?); 20-656 fms. Fossil. Post-tertiary or " glacial." Norway, Clyde beds, Siberia, Labrador, Canada, Maine. I agree with Professor G. O. Sars that this may be Moller's species; but the description is so short and indeterminate that it is almost equally applicable to L. tenuis. The late Professor M . Sars regarded it as a variety of the latter species, and as the Nucula yibbosa of James Smith. It is the Yoldia abyssicola of Torell, but not of M . Sars. The present species is gibbous ; and the anterior end is much more marked and upturned than in L. tenuis. PROC. ZOOL. Soc-1879, No. XXXVII. 37 |