Medusa and Ctenophora 17h 



One Narcomedusa, Aeginopsis laurentii, is likewise typically arctic. And, 

 like Sarsai princeps, it is not only large but very easily recognized; and it is 

 now known from so many records, so widely distributed over the Arctic seas, 

 that its presence can be considered a sure indication of arctic water. 



This is equally true of the Cteuophore Mertensia ovum, which is not only 

 a true arctic form, but is so sensitive to changes of temperature that it does 

 not long survive any considerable warming of the water in which it floats (1917, 

 p. 249). 



If further confirmation of the affinities of Sarsia princeps, Sarsia flammea, 

 Aeginopsis, and Mertensia be needed, it is furnished by^ the collection of the 

 Canadian Arctic Expedition, as it is for their circumpolarity. Indeed, to find 

 any shallow-water arctic Medusa not circumpolar would be surprising, there 

 being no barrier, either in the physical conditions of the sea water or in the 

 presence of a land mass, to such distribution. 



So far as the present collection goes, it may be considered a typical repre- 

 sentative of the endemic littoral Medusa fauna of the Arctic. 



POSTSCRIPT 



List of Medusa collected by the Canadian Exploring Steamer 

 " Neitune " 1903-1904. 



The few Medusae taken during this expedition are in poor condition, and, 

 as all belong to well-known species, a simple list of the records is given. 



Catablema vesicaria (A. Agassiz). 



One specimen, 20 mm. in diameter, with thirty large tentacles (all broken 

 off short) and about as many knobs, from Black Tickle, Labrador, September, 

 1903. 



Aglantha digitale (Fabricius). 



Three specimens, very fragmentary, 20-25 mm. high, port Burwell, Ungava, 

 September, 1903. 



Cyanea sp.? 



One specimen, about 35 mm. in diameter, too fragmentary for more than 

 generic determination, Fullerton, west side of Hudson bay. Northwest Terri- 

 tories, September, 1903. 



Aurelia limbata Brandt (?) 



Seven small specimens of Aurelia, 20-30 mm. in diameter, probably be- 

 longing to this species, because of the anastomosis of the canals (p. 14h), from 

 Black Tickle, Labrador, September, 1903. One specimen of about the same 

 size from North Somerset, Northwest Territories, August, 1904. 



BIBLIOGRAPHY. 



Agassiz, A. 



1866. North'American Acalephse. Mem. M. C. Z., 1. 14+234 pp., 360 figs. 

 AuriviUius, C. W. S. 



1896. Das Plankton der Baffin's Bay und Davis Strait. Upsala. Festschrift fur Lillje- 

 " borg, pp. 181-212. 



