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Show 582 DR. GWYN JEFFREYS ON THE MOLLUSCA OF THE [June 17, by its usually smaller size, thinner texture, having a rounder and less oblique outline, and being more uniformly convex; the posterior side is more abruptly angular; the beaks are more gibbous,and straight instead of inclining to one side ; the hinge-line is broader, and teeth fewer; and the cartilage and pit are shorter and smaller, and not placed so obliquely as in N. tenuis. N. macandrcei of Hanley. The young was named by me N. convexa ; and the fry appears to be the N. perminima of Monte-rosato. 3. NUCULA CORBULOIDES, Seguenza. N. corbuloides, Seg. Nuc. terz. merid. d'lt. p. 9, t. i. f. 3, 3a-h. 'Porcupine ' Exp. 1869 : St. 5, 6, 23, 40, 41. 1870 : Atl. 3, 16, 17, 17a. Fossil. Pliocene. Calabria and Messina district. This somewhat resembles the young of N. cegeensis, but is more triangular and gibbous, besides being closely and regularly striated in the line of growth. I had provisionally named it N. gibba. 4. NUCULA DELPHINODONTA, Mighels. N. delphinodonta, Migh. and Adams, in Proc. Boston Soc. Nat. Hist. i. p. 48 (1841) ; ii. p. 324, pi. iv. f. 5 (1842). 'Lightning' Exp.: St. 3. 'Porcupine' Exp. 1869: St. 65. Distribution. Davis Strait, 'Valorous' Exp., Norwegian arctic Exp. 1878, Norway from Vadsoe to Christianiafiord, N.E. America from G. St. Lawrence to B. of Fundy; 25-410 fins. Fossil. Pliocene. Sicily. N. corticata of Moller. The fry are oval. B. Edge crenated. 5. NUCULA TUMIDULA, Malm. N. tumidula, Malm in Scand. Naturf. Forh. viii. (1860), p. 621 : Got. K. Vet. Vitt. Samh. Handl. N y tidsf. viii. (1863), p. 122, pi. 2. f. 3. 'Porcupine' Exp. 1869 : St. 36, 39, 47. 1870 : Atl. 3a, 6, 9, Vigo B., 16, 17, 22,; Med. 55. A valve from the last station, at the depth of 1456 fathoms, is permeated by the same peculiar organism which I noticed in m y papers on Mollusca from the 'Valorous' Expedition. What is it ? Distribution. From Finmark to Bohuslan, Palermo, ' Challenger' Exp. (off Pernambuco) ; 20-650 fins. Fossil. Pliocene. Calabria and Sicily. It is the N. pumila of Loven MS., according to Asbjornsen=iV. nucleus ft in Ind. Moll. Scand. Not m y var. tumidula of N. nucleus, erroneously referred by m e to the present species, which I then knew only by a short description, not having seen Malm's figure or a specimen. The young in a fossil state has been lately described and |