1915O Fauna of the Chilka Lake ; Crustacea Decapoda. 213 



narrow ; the breadth of the fronto-orbital border is contained about four and one- 

 third times in the maximum breadth of the carapace. The frontal margin is straight* 

 not furrowed , with a single large, median tooth which projects over the otherwise 

 visible margin of the endostome. The dorsal surface of the front is coarsely pitted. 

 The orbit is very small, with distinct dorsal and lateral fissures, and beneath the eye 

 there is a small notch in the margin of the endostome. The orbit is in open communi- 

 cation with the antennular fossae and there is no space between the floor of the orbit 

 and the edge of the buccal cavern. 



The side walls of the hepatic region form an independent facet, bounded below 

 by a finely beaded ridge, which is strongly convex inferiorly. This ridge ends in 

 front close beneath the antero-lateral margin at the outer limit of the orbit; pos- 

 teriorly it joins the antero-lateral margin in a well-marked though obtuse angle. A 

 small prominence defines the junction of the antero- and postero-lateral margins and 

 behind this one or two small projections, the terminations of dorsal rows of tuber- 

 cles, are visible. The posterior margin is short, straight in the female and concave 

 in the male ; the outer angles are strongly marked in the former sex, while in adult 

 males they take the form of two large blunt teeth. 



On the upper surface of the carapace the cardio-gastric is separated on either 

 side from the branchial region by a shallow depression and the surface is still further 

 broken by the presence of blunt tubercles which form a definite pattern among the 

 fine granules with which the entire surface is covered. The tubercles are most 

 strongly developed in the adult male, but can readily be seen with the naked eye in 

 both sexes when the surface moisture has been removed. There is, in the first place, 

 a somewhat ill-defined patch of tubercles on the intestinal elevation. In front of 

 this, and not distinctly separated from it, is another similar patch on the cardiac 

 region, which is continued forwards to the gastric region as three ill-defined and 

 widely separated rows of tubercles, the lateral being obsolete in the female. In some 

 specimens the median row is continued as a very fine mid-dorsal carina up to the 

 front. 



The tubercles on the branchial region are, as a rule, more distinct than the rest. 

 On either side of the carapace, midway between the middle line and the lateral 

 margin, is a sinuous row of tubercles which curves outwards posteriorly and termin- 

 ates in the middle of the postero-lateral margin, the junction being often defined by 

 a slight prominence. In front of this row and parallel to its posterior portion is 

 another row of tubercles (less conspicuous in the female) which joins it near its 

 anterior end and is directed obliquely backwards and outwards culminating in a 

 distinct prominence in the anterior third of the postero-lateral margin. This row of 

 tubercles occupies much the same position as the two ridges in P. olivacea , Rathbun. 

 Seen in lateral view the figure formed by the tubercles resembles a cursive n. 



In the third maxillipedes the length of the merus measured along its inner 

 border is little less than that of the ischium. The flagellum is greatly expanded ; its 

 outer edge is strongly convex and the anterior end broadly rounded. The buccal 

 cavern is decidedly broader than long. 



