4 a , , Canadian Arctic Expedition, 1913-18 



The'northern Lymnaeas are extremely puzzling. I have had a large number, 

 including a series named by Morch from Beck's types in Copenhagen, with 

 which to make comparisons and I cannot detect from the shells any specific 

 ■differences between the form w« have called caperata Say, and the numerous 

 variations of the Greenland type which have passed under the name of vahli 

 Beck. I am disposed to regard all of them as boreal mutations of L- palustris 

 Miiller. 



The Physa is of unusual interest as the most northern species of the genus, 

 and the only one so far reported from the Arctic coast as properly restricted. 



A small collection was made at Orca, in Prince Willifim sound, containing 

 nine species which should be left out of consideration in discussing the Arctic 

 fauna. These, while incorporated in the general list, have not been included 

 in the present review of the Arctic species. 



Summary op Marine Si-ecies. 



Arctic species from the western Arctic area west of the Mackenzie River delta 72 



Arctic species from east of the delta 58 



Total : . . 130 



Species common to the two areas 30 



Acttial number of species 100 



New marine species 6 



The new marine species from east of the Mackenzie delta are: — 



F'seudamusium andersoni (PI. II, figs. 7 and 8). 

 Macoma oneilli (PI. II, fig. 1). 



Those from weSt of the delta: — 



Leda {Portlandia) collinsoni (PI. II, figs. 3 and 4). 

 Plicifusus johanseni (PI. Ill, fig. 1). 

 Volutopsius stefanssoni (PL I, fig. 1). 

 Margarites ecarinatus (PI. II, figs. 5 and 6). 



New fresh-water species: — 



Physa jennessi (PI. II, fig. 1). 



It will be noted that only five per cent of the marine species are character- 

 istically Eastern Atlantic forms, and with more thorough exploration of the 

 Western Atlantic fauna several cif these may prove to be circumpolar species. 



Of the forty-two western area species and the twenty-eight eastern area 

 species which were not collected in both areas by the expedition, none are' known 

 that are not found in some part of the western iarea. The fact that they were 

 not collected there by this expedition is purely accidental. 



When we examine a map and observe the vast gulf of the Polar sea heading 

 to the southeast in the passages eastward from cape Bathurst; and on the other 

 hand observe the narrow, tortuous, and ice-blocked passages which communicate 

 with the Greenland seas, it requires no further evidence to explain the failure of 

 the Eastern Arctic fauna to penetrate westward, or the success of the Western 

 Arctic species in colonizing the ground they occupy. 



Those who understand the difficulties which hamper the work of a collector 

 in these icy seas will feel appropriately grateful to Mr. Johansen and his associates 

 for these important contributions to our knowledge of the distribution of marine 

 life in a region so inaccessible to the ordinary collector. 



