MB. A. H. GEEEN ON THE BEAVEK. 361 



adopta the second species of Johnston's Northia, the N. concliy- 

 lega {Onuphis conchylcga of Sars). But I cannot see why M. 

 Mahiigrcn adopts Dr. Johnston's genus and at the same time 

 refuses to accept the species tuhicola as the type. For my own 

 part, I should have preferred retaining the genus Nothria for the 

 species tuhicola, and should have wished M. Malmgren had con- 

 stituted a new genus for conchylega. The only generic difference 

 between the two species, as far as I can see, consists in the 

 presence of the two postoccipital cirri in conchylega, and their 

 absence in tuhicola. Johnston does not seem to have seen these 

 cirri in the specimens of conchylega which he examined; and 

 Sars, who originally described the species, takes no notice of them, 

 either in his description or his figures (see Sars, Beskriv. og 

 Jaktt. p. Gl, tab. 10, fig. 28). Our British specimens of the 

 species are unfortunately imperfect, those from Berwick Bay (Dr, 

 Johnston's own specimens) consisting of tubes only and one frag- 

 ment of the animal ; while the specimens we possess from the sea 

 off the Shetland Islands, collected by Mr. Jeffreys, are equally 

 fragmentary, seven or eight specimens existing of the inferior half 

 of the animal only, not one having the head or anterior portion of 

 the body entire. 



It is just possible, therefore, that the Northia conchylega de- 

 scribed and figured by Sars and Johnston may turn out to be a 

 distinct species from that described by (Ersted, Grrube, Malm- 

 gren, &c., which not only possesses the postoccipital cirri, but, 

 according to ffirsted's figure and diGSCY\\)i\onoi Onuphis Eschrichti 

 (considered to be synonymous with conchylegahy Malmgren), has 

 also bipartite branchiae. 



On the Natural History and Hunting of the Beaver (Castor ca- 

 nadensis, Kuhl) on the Pacific Slope of the Rocky Moun- 

 tains, by AsHDOWN H. Gteeen, Esq. "With Supplementary 

 Notes by Eobebt Bbowjst, Esq., E.R.Gr.S. (Communicated 

 by James Mubie, M.D., F.L.S.) 



[Read November 5, 1808.] 



I HAVE have been for three years almost constantly engaged in 

 trapping beavers, so that what remarks I may have to make on 

 their habits and history, though somewhat at variance with the 



