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



Cei)haUc Shield. — The cephalic shield is very slightly raised above the general 

 surface of the body ; its posterior surface is furnished with a short blunt tubercle ; a slight 

 ridge separates the autero-lateral portions from the rest, as in other species. The eyes 

 are entirely absent, their place being occupied by a small tubercle similar to the rest of 

 the chitinous integument, and containing no traces of any optic structures. 



Tliorax. — The dorsal surface of the thorax, as well as the rest of the body, is very 

 much sculptured, more so than in any other species of the genus ; upon the epimera the 

 sculpturing takes the form of a network of ridges enclosing irregularly shaped roundish 

 pits ; the anterior half of the cephalic shield is sculptured in a similar fashion ; the posterior 

 part of the cephalic shield and the terga of the thoracic segments (especially upon their 

 posterior portions) are covered with thicker ridges anastomosing irregularly ; these are 

 most conspicuous ujion the lateral portions of the terga of the three anterior free 

 thoracic segments. The sculpturing ujjon the terga of the abdominal segments is very 

 slight. The scidpturing upon the caudal shield differed in different specimens ; in some 

 it resembled that of the epimera, in others the central portion between the median and 

 lateral carinje was occupied by a number of roundish irregularly scattered tubercles. 



The posterior margin of all the thoracic as well as the abdominal segments is pro- 

 longed in the median line into a short blunt tubercle ; these are larger upon the two last 

 thoracic and the abdominal segments. 



The first epimera are not divided into two portions by a suture ; the succeeding 

 epimera are closely applied to each other, the extreme end alone projecting freely ; they 

 are rather different in shape from what is customarily found in Serolis; instead of rapidly 

 narrowing towards the free extremit)' and terminating in a fine point, the anterior 

 margin runs parallel to the posterior margin of the previous epimeron until just before 

 the termination of the latter, when it passes abruptly backwards in a direction nearly 

 parallel to the long axis of the body, and joins the jiosterior margin almost at right angles. 

 The fifth and sixth ejiimera are more like those of other species. 



The epimera of the three anterior free thoracic segments are separated from the terga 

 bj- a suture. 



The sterna of the first two thoracic segments have the usual form (PI. III. fig. 4) ; the 

 median sclerite of the first segment is keeled, that of the second segment has a short keel 

 extending from the anterior extremity to about the end of the first third. The sterna 

 of the three posterior thoracic segments are similar to those of the last described species 

 {cf. PI. III. fig. 2) ; the male genital pores are very closely approximated in the middle 

 line. 



One of the male specimens pi'esents an abnormality in the presence of a pair of 

 ovigerous lamelL^ upon the third free thoracic segment ; the lamella of the right side was 

 about twice as large as that upon the left side. 



Abdomen. — The three anterior abdominal segments have been alreadv described ; the 



