1885.] 'lightning' AND 'porcupine' EXPEDITIONS. 35 



'Porcupine ' Exp. 1870 : Atl. St. 24, 27, 28, 28 a, 30 ; Med. Ad- 

 venture Bank. 



Distribution. North Japan (.S^^ John) ! 



This species may be known by the flattened apex and the remark- 

 able semicircular pad on the umbilicus, which is proportionally 

 much smaller than in N. josephinia. It is possible, however, that 

 the present species may be a southern, and therefore a smaller, form 

 or variety of N. affinis. The operculum in the Japanese specimens 

 is calcareous. It is also possible that my N. spheroides from the 

 'Valorous' Expedition (1/50 fathoms) may be the young of the 

 present species. 



16. Natica affinis, Gmelin. 



Nerita affinis, Gmel. ed. L. S. N. p. 3675 (ex Miill. Zool. Dan. 

 Prodr. no. 2956). 



Natica affinis, B. C. iv. p. 229 ; v. p. 215, pi. cii. f. 3; G. O. 

 Sars, Moll. reg. arct. Norv. p. 159, t. 21. f. 14 «, 14 b. 



'Lightning' Exp. St. 5. 



' Porcupine' Exp. 1869: St. 39, 65, 89. 



Distribution. Circumpolar and arctic seas in the Atlantic and the 

 Pacific, Iceland, Faroe Isles, between the Hebrides aud Faroes, 

 Norway, Labrador, Gulf of St. Lawrence, New England, Siberia, 

 Sea of Okhotsk, Aleutian I. (Dall), North Japan {v. Schrenck and 

 Lindholm) ; 1-1255 fms. 



Fossil. Pliocene: Red Crag {S. V. Wood). Post-tertiary: 

 Glacial beds in Greenland, Siberia, Iceland, Scandinavia, British 

 Isles, Palermo (Dr. van Geuns), Russia, and N. America ; 0-1360 ft. 

 The difference of level in Great Britain extends to 1840 ft., viz. 

 from the Shetland sea-bed, 480 ft., to Moel Tryfaen, 1360 ft. 



Synonyms. N. clausa, Broderip and Sowerby ; N. septentrionalis 

 (Beck), Moller; and as a variety, JV. occlusa of S. V. Wood and 

 N. russa of Stimpson. Prof. G. O. Sars considers N. affinis and 

 N. clausa distinct species, chiefly because of a difference in size and 

 in the radula. But in his figure of the larger form, which he names 

 clausa (t. 21. f. 12 b), the umbilicus is shown as quite open and 

 without any callosity. It has been said that even the good Homer 

 occasionally becomes sleepy ! The present species is not N. affinis 

 of Von d. Busch. 



The animals or soft parts of the typical form and the variety 

 occlusa or russa were described by me in my notices of the 

 ' Valorous ' Expedition. A specimen of the former is an inch aud 

 three tenths long, and nearly as broad. As to the greater size of 

 Invertebrata from Arctic seas, Mr. Norman remarks, in his " Notes 

 on the Oceanic Copepoda from Nares's Arctic Voyage : " — "With 

 respect to size, we find here, as in so many other instances among 

 the Invertebrata, an extraordinary development of the Arctic speci- 

 mens, which are at least six times the size of those from the Irish 

 coast, and measure five millimetres in length, exclusive of the an- 

 tennae." 



3* 



