REPORT ON THE ISOPODA. 171 



is convex and roughened by numerous minute tubercles; towards the posterior boundary 

 of each segment is a single row of short blunt spines. The lateral regions of the 

 segments have four projecting spines on each side, which are arranged in pairs one above 

 the other; the most anterior and dorsal of these spines is in every case the larger; the 

 spines are blunt and comparatively short. 



The fourth segment of the thorax has the form characteristic of other species of this 

 genus ; it is wider anteriorly than posteriorly ; the anterior part of the segment is as wide 

 as the foregoing segments, while the posterior part is of the same diameter as the 

 extremely elongated and narrow fifth segment; the dorsal surface is furnished with a 

 single row of short tubercles near to its posterior margin, and also a few tubercles 

 scattered over the anterior region. Along the lateral margin of the segment are about 

 eight spines, similar to those which fringe the lateral margins of the anterior segment. 



The fifth segment of the thorax is as long as the four anterior segments taken 

 together; the anterior part of the segment is elongated and narrow, the whole segment 

 resembling in shape the corresponding segment in other species of the genus. Along the 

 lateral margin is a row of about sixteen blunt spines, which pass uninterruptedly from one 

 end of the segment to the other ; there is also a double row of similar but less numerous 

 tubercles on the dorsal surface ; the dorsal and lateral tubercles are of about the same 

 size and about equal in length to the dorsal tubercle of the preceding segments. The 

 hinder part of the segment has a median longitudinal ridge, which is continued on 

 to the succeeding segments of the thorax. 



The sixth and seventh segments are very short and subequal in antero-posterior 

 diameter ; the breadth of the sixth segment is somewhat less than that of the posterior 

 part of the fifth segment; the seventh segment is narrower still. The anterior margin 

 of the segments is convex, the posterior margin concave. The dorsal region of the 

 segment is beset with a few scattered tubercles, and the lateral margins have also a number 

 of short spines which are like those of the fifth segment, and much shorter than those 

 upon the three first segments. 



The abdomen is oval in form, and, as in other species, provided with a median 

 convexity which runs nearly to its extremity. The anterior part of the abdomen is 

 separated off from the rest and forms a distinct free abdominal segment. This segment 

 is divided from the rest of the abdomen by a notch on either side, in front of which is a 

 pair of short spines. The lateral regions of the abdomen have on either side three short 

 spines, one being placed just in front of the point of articulation of the uropoda. The 

 abdomen terminates a little way behind the uropoda in a bifurcate extremity, as shown 

 in the accompanying figure (woodcut, fig. 1). 



There are no traces of the antennules or antennse, except the large basal joint of the 

 former appendages. 



The thoracic appendages are very similar to those of Ischnosoma spinosum, the joints 



