122 THE NAUTILUS. 



to Long Island as a terminus. The sound is not deep and tides not 

 great, this barrier would be and was crossed. The eastern coast is 

 different. The trend of the ice, though slightly deflected towards 

 the east, was in a southerly direction ; comparatively little passed off 

 the east coast. Add now a study of Greenland, as it is under conti- 

 nental glaciation conditions and probably exactly as New England 

 was. Peary's exploration shows a range of animals like the musk- 

 ox, arctic wolf and others at Independence Bay, and practically the 

 extreme northern limit of Greenland, and this implies food on which 

 they live. In other words, Greenland under a glacier yet has a 

 shore line of animal and vegetable life. The distribution of H. 

 hortensis fits the theory that it is a survivor. The present abodes 

 are such that it could not have been carried from one to the other 

 and not have found a home on the mainland more than it has. On 

 the other hand Grand Manan, outer islands in Casco Bay, the ex- 

 tremity of Cape Ann and Cape Cod, are places that would be last 

 resorts. A more exhaustive treatment of the subject would deal 

 with elevation and subsidence, possible islands or land in the east 

 now submerged. The stronger tides that would break up a mass of 

 ice extending seaward. I leave these topics and present only the 

 imple suggestion. 



A NEW SPECIES OF PERIPLOMA FROM CALIFORNIA. 



BY WILLIAM HEALET DALL. 



Periploma sulcata n. s. 



Shell rotund, white, with the left valve flatter, thin, sculptured 

 with numerous, close-set, irregularly concentric, more or less inter- 

 rupted, low ridges, separated by subequal shallow interspaces ; the 

 surface is also microscopically shagreened, and there is a low rib ex- 

 tending from the beak to the lower margin of the ill-defined rostrum 

 and an ill-defined furrow radiating from the beak toward the anter- 

 ior base, in the right valve; beaks low, distinctly fissured ; anterior 

 dorsal hingeline rounded, posterior ditto, shorter, nearly rectilinear, 

 forming with the elevated rib a subtriangular space which is free 

 from the undulations which cover the rest of the shell ; interior 

 shining, hardly nacreous, the muscular impressions very small, the 

 pallial line obscure ; chondrophores pvominent, spoon-shaped, extend- 



