14 Proceedings of the Royal Society of Victoria. 



Head. — The head is very convex on the dorsal and anterior 

 surfaces. The anterior end, as seen from above, is truncate. 

 The anterior margin has a slight V-shaped cleft immediately 

 below the level of the eyes. From the anteroinferior margin of 

 the head a strong furrow runs upwards and then backwards, 

 parallel to the long axis of the body, and reaches as far as the 

 posterior end of the head. This furrow divides the head into 

 two well-marked portions, the upper of which has the form of a 

 quarter of a sphere, while the lower, as seen from the side, is 

 oblong and forms a prominent convex cheek. The transverse 

 depression mentioned by Chilton in P. australis and in P. 

 assimilis is absent in the present species. 



Eyes.- — The eyes are as in P. australis, except that they consist 

 of about forty lenses, in proportion with the greater size of the 

 animal. 



Pereion. — The first segment of the pereion is fused to the head, 

 the line of union being strongly marked. The Krst segment is 

 very little narrower than the second. The anterior and posterior 

 dorsal edges are straight, and parallel to one another. In side 

 view the segment widens slightly and is bent forwards in close 

 apposition to the side of the head. The sides of the segment are 

 globose and larger than in the case of the succeeding segments. 

 The second, third and fourth segments are all of about equal 

 size. The inferior margins (epimera) of each segment have a 

 notch in the centre for the reception of the basi of the legs. 

 The anterior angle is thickened and slightly produced downwards. 

 In the fourth segment the posterior angle is formed by a slight 

 flat fold, which gradually decreases in size in the preceding 

 segments until, in the first, it forms merely a ridge which does 

 not reach the posterior angle. The epimera of the fifth, sixth 

 and seventh segments are broadly notched. The anterior margin 

 of the fifth segment is produced forwards into a broad, rounded 

 plate. The corresponding plates in the two succeeding segments 

 are smaller and more angular in shape. The posterior marginal 

 plates are of the same size in the three segments, that of the 

 seventh segment being of about the same size as the anterior one. 



Pleon. — The first segment is narrower than the seventh 

 segment of the pereion, and gradually narrows as it passes 

 downwards. It extends downwards considerably beyond the 



