20 G. 0. SARS. CRUSTACEA. [norw. POL. EXP. 



the solitary specimen procured having been taken in the Pacific, at some 

 distance from Tahiti. The genus was justly placed in the extensive family 

 Lysianassidm, though in some characters it differs rather markedly from 

 the other known genera. It was, indeed, very surprising to find this genus 

 represented in the Polar Sea by a well-marked and very beautiful species; 

 and I had intended to dedicate it to our celebrated explorer. Prof. Nansen. 

 The same species, however, has been quite recently recorded by M. E. Chevreux 

 from the Expedition of the Prince of Monaco, and, as nothing has as yet 

 been published about the Crustacea of the Nansen Expedition, the name pro- 

 posed by M. Chevreux for this species ought of course to be retained. The 

 species will be described in detail below. 



5. Cydocaris Guilelmi, Chevreux. 

 (PI. II & III). 



Cydocaris Guilelmi, E. Chevreux, Bulletin de la societe zoologique de 

 France, T. XXIV, 1899, p. 148. 



Remarks. The present species is nearly related to the Pacific form 

 described by the Rev. Mr. Stebbing as C. tahitensis, though evidently speci- 

 fically distinct, being not only of considerably larger size, but also differing 

 in some of the structural details, as will be seen by comparing the figures 

 here given with those reproduced in Mr. Stebbing's Avork. On the other 

 hand, no doubt can arise as to the identity of the Polar form with that 

 recorded by M. Chevreux under the above name. 



Description of the Female. 



The length of the largest specimens in the collection is about 18 mm. 

 Those examined by M. Chevreux were somewhat smaller, measuring from 

 11 to 12 mm. 



The general form of the body (see PI. II, fig. 1) is moderately slender 

 and somewhat compressed, with the mesosome slightly exceeding in length 

 the metasome and urosome combined. The back is quite smooth throughout, 

 and generally slightly curved. 



The cephalon (see also fig. 2) is rather thick and massive, and, from 

 a lateral point of view, quadrangular in form, being transversely truncated 



