296 Th. Mortensen. 



Asterias MüUeri is not knovn from the American East Coast, 

 but otherwise from the whole North Atlantic (Iceland, Færoes, 

 Britain, North Sea and the Danish Seas); along the Norwegian 

 Coast it passes to the Kara Sea, the Siberian Ice Sea and perhaps 

 even to the Bering Sea. Fischer records it from Jan Mayen (Oesterr. 

 Polarstat. Jan Mayen. 1886. p. 31). I would suggest that this is per- 

 haps a mistake for the var. grønlandica. The typical Ast. MüUeri is, 

 as seen by the distribution, decidedly a boreal form, though one of 

 more eurytherm nature than other boreal species. Probably the 

 temperature would not be a hindrance to its living at Jan Mayen, 

 but as it is unknown at the North-East Coast of Greenland and at 

 Spitzbergen, it seems very remarkable that it should have reached 

 Jan Mayen, though — as is well known — it has not pelagic larvæ. 



The distribution of the species Solaster endeca, glacialis and 

 squamatus cannot be made out with full certainty as yet, these spe- 

 cies having only recently been cleared up (through the researches 

 of Döderlein and Grieg), while they were previously confounded 

 under the names S. endeca and papposus. It is, how^ever, evident 

 that the species glacialis and squamatus are arctic species, probably 

 developed in the Northern Sea, while S. endeca is a boreal species^ 

 though one wdiich is not bound to the warm water. The fact that 

 it reaches a larger size at the northern coasts of Norway than at 

 the West Coast (Grieg. "Mich. Sars" Asteroidea. p. 66) seems to 

 indicate that it prefers a somewhat low^ temperature, a fact in 

 accordance with its occurrence in the littoral region of Greenland. 



Pteraster pulvillus is evidently an arctic species, known from 

 the arctic region of the East coast of North America, the East 

 Coast of Greenland, Spitzbergen, the northern Coast of Norway 

 and from the Siberian Ice Sea. It must be supposed to have 

 developed in the Northern Sea. Its occurrence at North America 

 may perhaps be accounted for by its having wandered round the 

 South Coast of Greenland, across the Davis Strait (over the ridge?), 

 in a former colder period. This would seem to be the natural 

 explanation of its recent distribution in case it is really not found 

 at the West Coast of Greenland (especially to the North). Our pre- 

 sent knowledge of the fauna from the Baffms Bay northwards is,, 

 however, scarcely sufficient for proving definitely its non-existence 

 in these waters. 



Poraniomorpha tumida is likewise a purely arctic form, known 

 only from the Polar Sea, from the East Coast of Greenland to the 

 Siberian Ice Sea. It is not known from North America. 



Pedicellaster palœocrystallus is hitherto known with certainty 

 only from the northern Greenland, bul il can scarcely be doubted 



