The, Invertebrate Fauna of the Uitenliagc Scries. 215 



antero-ventral margins which form a broadly convex outline. Their 

 truncated posterior borders are slightly sinuous being projected 

 backwardly just below the articular socket, and having a slightly 

 excavated outline below this. The posterior borders bear minute 

 marginal denticles, and they form a roughly rectangular junction, 

 below, with the antero-ventral border. There is a shallow vertical 

 groove on the surface near the posterior border, and the pleuron also 

 bears granular and pitted ornaments on its upper and posterior parts. 

 Posteriorly situated, on its lower half, are two short, parallel, raised 

 ridges bearing several minute tubercles : these have a transverse 

 (horizontal) direction, and the lower is the shorter of the two. On 

 the pleura of the succeeding three segments (iii.-v.) the ornaments 

 are similar, but the horizontal tubercular ridges become reduced in 

 size, particularly in the fifth segment. The pleura of these segments 

 are much less extensive than those of the second segment. Those 

 of the third and fourth segments are pointed below, with sloping, 

 slightly convex, antero-ventral borders, with narrow smooth raised 

 marginal lip and straight posterior borders furnished with a row of 

 minute denticles. The pleura of the fifth segment are more broadly 

 rounded below. Those of the sixth segment are very reduced in 

 extent and have the posterior half of their inferior margin broadly 

 excavated to allow of the free movement of the expanded swimming 

 appendages of this segment. The pleura and tergum of this segment 

 are alike ornamented with minute tubercles. 



The tergum of the first abdominal segment has a shallow groove 

 rising from the articular sockets and curving slightly forwards as it 

 crosses the back. Similar grooves occur on the succeeding four 

 segments, two on either side of each tergum. They arise at the 

 (anterior) articular facet and the (posterior) articular socket and 

 slightly converge as they pass up towards the dorsal arch of the 

 tergum. The anterior groove on the second segment may be traced 

 across the back, but the remaining grooves become very faintly 

 marked or disappear on the dorsal parts. On the sixth segment, 

 the corresponding anterior groove is very strongly marked, and 

 passing right across the back, defines an anterior, convex, lenticular 

 shaped tergal facet which fits under the posterior part of the fifth 

 tergum. There is also on either side, in the posterior half of the 

 segment, a horizontal groove, separating the pleuron from the 

 tergum, and these pass posteriorly into a very weak shallow groove 

 which runs across the tergal arch close to the posterior border of the 

 segment. 



The telson is relatively narrow and elongated. Its sides form 



