REPORT ON THE ISOPODA. 45 



Ischnosoma bacilloides, F. E. Beddard (PL VI. figs. 8-13). 



Ischnosoma bacilloides, F. E, Beddard, Proc. Zool. Soc. Lond., 188R, pt. i. p. 99. 



The present species, like the last, consists only of a fragment, which is fortunately 

 nearly perfect so far as it goes ; the fragment corresponds almost exactly to the already 

 described fragment of Ischnosoma bacillus ; it has lost, however, a portion of the fourth 

 segment of the thorax, corresponding to its epimera, i.e., to the arms of the T in Ischnosoma 

 bacillus ; so at least I am led to interpret the appearances presented by this region of 

 the body ; there is evidently a suture on either side at the anterior end of the segment, 

 but it is not quite certain whether the broken fragments, which during the life of the 

 animal were clearly articulated to the sutural margin, belong to this segment, or whether 

 they are really portions of the segment in front, the fourth segment being in that case 

 without epimera ; in the latter case there will be another difference between the two 

 species in addition to those which I shall point out in the following description. 



Of this species, as of the last, there was only a single fragment obtained off the west 

 coast of South America in 1450 fathoms ; the depth at which this species lives is not 

 widely different from that of Station 158, at which Ischnosoma bacillus was obtained 

 (1800 fathoms), and the latitude is nearly the same. 



The fragment measures 1 1 mm. in total length and the proportion of the segments 

 is about the same as in Ischnosoma bacillus. 



The general aspect of the body, as may be seen by a comparison of figs. 6 and 8, is 

 exactly the same in both species. 



The fourth segment of the thorax appears to be similar to that of Ischnosoma bacillus, 

 but it is impossible to speak with certainty for the reasons already given. 



The fifth segment of the thorax, like that of Ischnosoma bacillus, is the longest and 

 has the same form as in that species ; the epimeral spines, however, instead of being, as 

 in Ischnosoma bacillus, directed outwards at right angles to the longitudinal axis of the 

 body, or at most with a sbght forward flexure, are unmistakably bent backwards. The 

 sixth segment, however, presents the most striking difference between the two species, 

 and serves at once to distinguish them ; it is in fact provided with long spiniform 

 epimera precisely similar to those upon the segment in front, and like them bent backwards, 

 though at a somewhat greater inclination with the longitudinal axis of the body. 



The seventh and last segment of the thorax is similar to that of Ischnosoma 

 bacillus. 



The abdominal shield is rather more circular in form than in the last species, and the 

 distinction between its anterior and posterior regions is therefore more marked ; the 

 posterior region of the caudal shield as it approaches its termination is rather bent 

 upwards. The same is the case with Ischnosoma bacillus. The abdominal shield is 

 preceded as in that species by a narrow free abdominal segment. Owing to the fact that 



