EEPOET ON THE ISOPODA. 59 



I take the opportunity of naming this species after Professor Gr. 0. Sars, who has so 

 largely increased our knowledge of this as of other families of the Crustacea. 



The specimens in question are a male and a female. The female is rather the larger 

 of the two, measuring 24 mm. in length, by 1 1 mm. in greatest breadth ; the difference 

 in length between the two specimens appears to be entirely owing to the fact that the 

 anterior thoracic segments are longer than in the male to make room for the attached 

 ovigerous lamellae. Otherwise the two sexes appear to present no recognizable differences. 



The species was also obtained at Station 147, from a depth of 1600 fathoms. 



In no case, unfortunately, are any of the thoracic limbs or the antennae preserved, a 

 fact which is to be the more regretted, as the modifications of the thoracic limbs are 

 precisely those characters which have largely served Professor Sars as a means of 

 dividing the group into its several genera. It is not the possibly rough handling of the 

 specimens themselves when being transferred to spirit that has injured them in this way ; 

 some manuscript notes by Dr. v. Willemoes Suhm state that this species was never 

 dredged with its limbs complete. As it is, in all the specimens, five in number, there are 

 only the first joints of the ambulatory appendages left adherent to the body. 



The head segment is about equal in size to that of any of the anterior segments of the 

 thorax. 



The first four segments of the thorax are of about the same antero-posterior diameter, 

 the fourth alone being rather narrower than the three which precede it. 



The breadth of these segments, their diameter from side to side, progressively 

 increases so that the fourth is the widest ; the anterior margin of each is rather concave 

 forwards, the posterior margin convex backwards ; the fourth segment, however, has its 

 two margins ajDproximately straight and parallel ; the posterior margin is slightly concave 

 instead of convex ; this segment, in fact, forms the middle point of the body, in front 

 of it the segments are curved forwards, behind it they are curved backwards. 



The upper surface of the body is entirely devoid of spines or tubercles of any kind, 

 which are often characteristic of other species of the genus. 



Each of the four anterior thoracic segments is somewhat saddle-shaped, its anterior 

 and posterior margins being produced into a ridge, and the central part between the two 

 ridges depressed ; laterally, the posterior ridge widens out into a triangular convex 

 area which occupies the whole of the segment just behind the articulation of the epimera ; 

 this convex area does not, however, become fused with the anterior ridge of the segment, 

 bat remains distinct from it ; the latter terminates on either side in a short, forwardly 

 directed, spiny process, which becomes progressively longer in the segments passing 

 from before backwards, and is indeed hardly visible in the first segment of the thorax. 



The epimera of these segments are conspicuous ; a transverse line of division, 

 approximately parallel to the transverse axis of body, divides each epimeron into two 

 halves, an anterior and a posterior; the former is produced into a longish spiny 



