582 DR. GWYN JEFFREYS ON THE MOLLXJSCA 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 

 JV. 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, 2>a-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 JV. 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. 



I 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 Christiania fiord, 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, 



2V. tumidida, Malm in Scand. Naturf. Fcirh. viii. (I860), p. 621 : 

 Got. K. Vet. Vitt. Samh. Handl. Ny 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 my papers on Mollusca from the 'Valorous' 

 Expedition. What is it? 



Distribution. From Finmark to Bohusliin, Palermo, ' Challenger ' 

 Exp. (off Pernambuco) ; 20-650 fins. 



Fossil. Pliocene. Calabria and Sicily. 



It is the N. pumila of Loven MS., according to Asbjdrnsen=2V. 

 ■nucleus ft in Ind. Moll. Scand. Not my var. tumidula of N. nucleus, 

 erroneously referred by me to the present species, which I then knew 

 only by a short description, not having seen Malm's figure or a spe- 

 cimen. The young in a fossil state has been lately described and 



