CRUSTACEA — WIIITELRfJCiK. 



205 



A loiiti;itu(liiial su])ine(li!in pair of cavin;o coiiimcnce on tlic 

 rostral spine and are continued to the ceplialic suture; at this 

 point they unite and form a single median keel, 

 which ceases at a short distance from the acutely 

 ridged hinder margin. 



There is a low longitudinal ridge on each side, 

 connnencing at the antero-latferal angle of the 

 front and terminating near the sutural depres- 

 sion ; the latter marks the limits of four short 

 longitudinal ridges, of which the posterior pair 

 subtends the median and the anterior pair the 

 submedian carint>3. 



Second (first free) segment as wide as the first, 

 but a little shorter, third segment shorter than 

 the fourth and about one-third longer than the 

 seventh, the fifth and sixth are subequal in length 

 and breadth. 



All the free segments are marked superiorly by 

 a well defined median keel and a submedian pair ; 

 the latter varies in length on the different segments. 

 On the second they extend along the whole length 

 of the segment, on the third they are confined to 

 the posterior two-thirds, and on the remaining 

 segiaients of the peraeon they commence about 

 the middle and terminate at the posterior border. 



The submedian ridges are bounded on each side 

 by a pair of short transverse ridge-like tubercles ; 

 the larger one is seated on the anterior border 

 and the smaller about the middle of the segment ; 

 they are separated by a narrow transverse 

 depression. Body viewed from 



" ' ' ' ABOVE. 



The second, third and fourth segments of the 

 peraeon are widest in the middle ; the sides when viewed from 

 above have an evenly curved outline ; fifth, sixth and seventh 

 segments wider behind than in front, the marginal outline being 

 oblique and bidentate. 



Each epimeral process bears a pair of strongly marked ridges. 



Coxal joints of the second pair of legs, with a small angular 

 spine-tipped process, directed outwards and forwards; each suc- 

 ceeding coxa bears a broad incisor-like lobe ; the lobes of the 

 third and foui^th are overhung and almost concealed by the 

 epimeral processes, but those of the succeeding segments are very 



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