64 THE VOYAGE OF H.M.S. CHALLENGER. 



from Stations 147 and 237. The distribution, geographical and bathymetrical, of this 

 species is of some little interest, and is, I venture to think, confirmatory of an opinion 

 which I have elsewhere expressed, respecting the distribution of the deep-sea Isopoda. 



In my report on the genus Serolis 1 I pointed out that the distribution of two 

 species, Serolis bromleyana and Serolis antarctica, was confirmatory of Gerstaecker's 

 view that, to the south as well as to the north of the equator, the depth at which a 

 species is found increases progressively with its distance from the equator. 



The distribution of Eurycope fragilis does not bear out this view at all, but 

 does support my own view that the size of the individuals increases as the species passes 

 south. The specimen of Eurycope fragilis from Station 152 is three times the size 

 of any of the specimens dredged at Station 237, while the single specimen from 

 Station 147 is not only intermediate in geographical position, but also in size between 

 the other specimens. So possibly with Eurycope atlantica, if I am right in assigning 

 the fragment from Station 147 to that species; the individual from the North Atlantic 

 is considerably smaller than that from Station 147 ; in this instance increase of size is 

 correlated with the increase of depth in the habitat, but I am not inclined to lay any 

 stress upon this relation as it is not borne out in the other species. 



The largest specimen, that from Station 152 (1260 fathoms), measures 30 mm. in 

 length ; the individual from Station 147 measures 17 mm. in length, that from Station 

 158 about the same; the largest of the series of small individuals from Station 237 

 measures only 12 mm. 



The following description of the species is, as already stated, based upon these smaller 

 specimens, because they happen to be better preserved than any of the larger individuals. 



The head is long, but narrower than the first segment of the thorax ; the first four 

 segments of the thorax are subequal in antero-posterior diameter, but increase gradually 

 in breadth ; the second, third, and fourth of these segments, or the third and fourth only, 

 have a longish spine in the median dorsal line. The antero-lateral margins of the 

 segments are prolonged into a short, forwardly directed spine, in the third and fourth 

 segments only ; the epimera of all these segments are furnished with a long spine, 

 considerably longer than that of the tergum, but following the same general direction ; 

 in the first two segments of the thorax there is only one epimeral spine ; in the three 

 succeeding segments there is an additional shorter spine. 



The three posterior segments of the thorax have the form which is characteristic of 

 the genus ; the body of the species is widest at the first of these segments. 



On the ventral surface of the thoracic segments are a number of short spines ; on each 

 of the first four segments is a single short spine in the median line; these increase in 

 length progressively from the first segment backwards ; there are a series of similar 

 spines, but apparently stouter, upon the last thoracic segments, and one short conical 



1 Zool. Glial], Exp., part xxxiii. p. 82. 



