445 Canon A. M. Norman on British Isopoda. 



This fine species would seem to be subject to an amount 

 of variation which is very unusual, or else there are several 

 closely allied forms. I prefer to regard these forms as 

 varieties. If hereafter writers are of a different opinion, the 

 names here employed can be raised to specific rank. 



[Var. 1. typica. 



It is this form which all the figures above referred to 

 illustrate. It is furnished with highly elevated, conical, 

 spiniformed processes, arranged in transverse pairs and 

 developed on all the segments of tlie body. The figure 

 in 'The Depths of the Sea' is excellent, and illustrates 

 the habit of the genus in carrying its young attached 

 to the antennae. The specimen which the figure referred 

 to illustrates was taken by the * Porcupine ' Expedition, 

 1869, Stat. 59, lat. 60° 21' N., long. 5° 41' W., in 

 580 fathoms — that is, in the cold area of the Faroe Channel. 

 My own collection contains specimens from Bafiin's Bay 

 (^Albany Hancock) and Greenland [D'Arcy Thompson). 



[Var. 2. intermedia. 



In this variety the tubercles are greatly reduced in size 

 and elevation on the iiead and first four segments of 

 mesosome, but on the fifth and succeeding segments they 

 are as well represented as in the typical form. Baffin's 

 Bay [Albany Hancock, in Mus. Nor.). 



[Var. 3. tuberosus, G. O. Sars. 



1876. Arcturus tuberosus, G. O. Sars, I. c. p. 350. 



1877. Arcturus baffini, \a.x., Feildeni, Miers, "Report Crust. Arctic 

 Exped. 1875-1876," Ann. & Mag-. Nat. Hist. ser. 4, vol. xx. p. 14, 

 pi. lii. fig. 1. 



1885. Arcturus tuberosus, G. 0. Sars, I. c. p. 102, pi. ix. fig. 22. 



"^ Without distinctly perceptible hairs and without dorsal 

 spines, but presenting an irregular rugged surface'' (G. 0. 

 iSars). The type of Sars measured 35 mm., but I have seen 

 an example 60 mm. Greenland (D'Arcy Thompson, in 



Mus. Nor.). 



l^Aixturus scahrosus, sp. n. 



In general character as A. hciffini, but somewhat more stoutly 

 built. Dorsal surface entirely devoid of spines or elevated 

 tubercles, but extremely rugged, covered with depressed 

 nodules; the entire surface, including the nodules, covered with 

 granules of considerable size. These granules not only cover 



