102 PKOCKEDINGS OF THE M ALACOLOGICAL SOCIETY. 



The Challenger dredged Area corpulenta off jVoith-East Australia in 

 1,400 fathoms, in mid- Pacific in 2,425 fathoms, and near Juan 

 Fernandez in 1,375 fathoms ; Lima goliath off South Japan in 

 775 fathoms, and off South Patagonia in 245 fathoms. 



It is obvious, however, that our ability to study the vital 

 conditions which govern the existence of the MoUusca, not only in 

 these great depths, but even in comparatively shallow water, is 

 infinitesimal as compared with our opportunities of studying the 

 life conditions of Mollusca which live habitually between or not far 

 below tide-marks. In the one case we can only do a little scraping 

 of the bottom here and there, in the other we have the coastline of 

 all the seas in the world to work upon. It seems possible that in the 

 zeal for deep-sea exploration, which has been prosecuted with such 

 signal success in every branch of marine zoology for more than forty 

 years, we may have lost sight of the rich harvest of knowledge which 

 must assuredly be reaped by a further study of the habits, mode of 

 life, and distribution of tlie shore fauna, using the term to include 

 the shallow-water fauna as Avell. 



Let me indicate a few problems of distribution whicli may be said 

 to be waiting for solution. 



How does it come about that Siphonuria, a littoral genus whicli 

 occurs in a ])rofusion of individuals wdierever it is found, is common 

 tliroughout the Tropics, and ranges as far south as Cape Horn, tlio 

 Falklands, St. Paul's Island, and Kerguelen Island, in an area of cold 

 water, whose surface temperature in winter barely exceeds 40° F., 

 and even in summer does not exceed 50° F., while at the same time, 

 in European seas, it only reaches a point on the Spanish coast, some- 

 where north of Cadiz, where the summer surface temperature is 

 68° F. and the winter temperature is scarcely less than 60° F. '? 

 The same phenomenon is repeated on the south-east coast of North 

 America, where Siphonaria lineolata, Orb., reaches its extreme northern 

 range in Georgia, and S. alternata. Say, in East Florida and in 

 Bermuda. On the other hand, on the west coast of North America, 

 a species {S. tkersites, Carp.) is reported from Vancouver and up to 

 57° N. lat.^ Is it possible that at the present moment Siphonaria 

 is spreading northward along the western shores of Europe and the 

 eastern shores of America? If not, special investigation might throw 

 light on the anomalies of its distribution. 



The geographical range oi Patella forms another subject of interest. 

 It is a remarkable fact tluit, although many of our own littoral mollusca 

 occur on the eastern and some also on the western coasts of North 

 America, botli East and West America, north of the Tropics, are 

 destitute of Patella proper altogether. If we nuvy assume that the 

 focus of distribution of a genus is the area, be it great or small, within 

 which the genus attains its largest number of species and its general 

 maximum of development, the foci of the distribution of Patella are 

 South Africa, and to a much less considerable extent Southern 



1 P. P. Carpenter, Eeport, 1863, p. 133 (647) ; G. W. Taylor, Trans. Roy. Soc. 

 Canada, ser. Ii, vol. i (4), pp. 17-100, 1895. 



