of the Fishery Board for Scotland. 



213 



with three slender processes ; two of them are prolongations of the 

 lateral angles, and the other of the intermediate angle by which the 

 posterior edge of the plate is divided into two sub-equal portions. It has 

 to be noted, however, that these dorsal expansions are so extremely 

 delicate that, though many specimens have been examined, it was rare to 

 find one with the appendages uninjured. The following is M. Hesse's 

 description of the posterior dorsal plate : — "Enfin la sixieme expansion 

 membraueuse que est aussi triangulaire comme celle placee sur l'occiput, 

 est fixee un peu audessus de la base de l'abdomen qu il recouvre, et 

 semble destine a prot^ger les oeufs ou les embryons. Son bord inferieur 

 pr^sente deux ddcoupares, terminees per trois lanieres, dont l'une est au 

 milieu et les deux autres a l'extremite du bord inferieur." 



The cephalo-thorax in the female is comparatively large, and consists of 

 five segments ; in adult specimens, however, the segments are not very 

 clearly defined. The first four do not differ much in size, but that 

 which forms the head or cephalosome is rather smaller than the others. 

 The last segment is fully twice the length of the preceding one, and is 

 composed of two coalescent segments — the fourth and fifth segments of 

 the metasome. This double segment is destined, as in other members of 

 the iVotodelphyoida, to be a receptacle for the eggs and developing larvae, 

 and when packed with eggs or larvae it becomes considerably enlarged, 

 and is also more highly coloured than other parts of the animal. (See 



% i.) 



In the female the abdomen — urosome — is moderately elongated, 

 slender, and cylindrical, and is composed of five segments, but the 

 prefurcal segment is very small and of a peculiar structure, and seems to 

 overlap the base of the short furcal joints. These joints, which are 

 somewhat arcuate, are each armed with about four very short but strong 

 curved spines (fig. 19). 



Neither the male nor the young female appears to be furnished with 

 the prominent dorsal appendages possessed by the female that has 

 reached the ovigerous stage. Figure 3 represents a young female with an 

 adult male adhering to its dorsal surface, in both of which the wing- 

 like expansions are wanting. The female appears to have reached the 

 stage when these expansions Bre beginning to be developed, but in the 

 male no trace of them can be observed, though its structure shows it to 

 be a mature example. 



In the specimens under consideration the antennules (anterior 

 antennae) are in both sexes apparently nine- jointed. In those of the 

 female the first two joints are of large size, but the remaining joints are 

 considerably shorter and narrower, and the second and third from the end 

 are smaller than any of the others. The male antennules are moderately 

 stout and taper gradually towards the distal extremity ; the first two 

 joints are not so dilated as the first two in the female, but the remaining 

 seven joints are rather larger. (See figs. 4 and 5.) 



The antennae (posterior antennae) of the male, though considerably 

 smaller than those of the female, are similarly armed with strong 

 terminal claws, as shown in figs. 6 and 7. 



The mandibles are well developed and possess a broad, biting edge, 

 armed with several irregular teeth ; the mandible-palp is moderately 

 large and two-branched ; the proximal branch appears to be uni-articulate, 

 but the other is two-jointed ; both branches bear plumose setae (fig. 8). 



The maxillae (fig. 9) are also moderately developed and supplied with 

 numerous plumose setae. 



The first maxillipeds have the basal part greatly enlarged and 

 provided with a number of long plumose setae on its inner margin ; the 



