146 SMITHSONIAN MISCELLANEOUS COLLECTIONS 



of a septum between the antennulse and the equahty in size of the 

 meros and ischium-joints of the outer maxilhpeds. The orbits 

 appear nearly the same in both. Characters derived from the orbits 

 and eyes (as "retractile" and "non-retractile") are as difificult of 

 apprehension here as among some Maioids. 



241. HALICARCINUS OVATUS Stimpson 



Halicarciniis ovatus Stimpson, Proc. Acad. Nat Sci. Phila., x, p. 109 

 [55], 1858. 



Carapax subovate, narrowing before. Length and breadth nearly 

 equal. Upper surface smooth, flattened in the male, somewhat con- 

 vex in the female. Regions generally sufficiently distinct, separated 

 by linear sulci. Lateral margins angular, with a small acute tooth 

 at each angle, of which there are two on each side of the carapax. 

 Front prominent, with three deeply cut, closely appressed, equal, 

 flattened teeth projecting from beneath the straight supra-frontal 

 margin, but nearly at the same level. Internal antennae large. 

 Epistome moderately large. Buccal area of moderate size, closed 

 in front : maxillipeds somewhat convex or protuberant. Chelipeds 

 of male subclavate, smooth, sparsely hairy within ; meros with a 

 small tooth at summit ; hand with rounded, swollen palm and rather 

 slender fingers minutely serrated within. Ambulatory feet long and 

 slender, naked ; a small, sharp tooth at the summit of the meros- 

 joint. The feet of the middle pairs are a little more than twice as 

 long as the carapax. Dactyli falciform, and slender from the base 

 throughout. Abdomen of the male contracted near the extremity ; 

 terminal joint subcordate. obtuse. Dimensions of carapax in a 

 male: Length, 0.251 ; breadth. 0.252 inch. 



Taken in Port Jackson. Australia. 



Genus TRIGONOPLAX Milne Edwards 



242. TRIGONOPLAX TRUNCATA Stimpson 



Trigcnoplax tnincata Stimpson. Proc. Acad. Nat. Sci. Phila.. x. p. 109 

 \55]. 185S. 



Carapax not indurated, rounded-ovate, smooth, above flat or 

 slightly concave in the male, slightly convex in the female. Propor- 

 tion of length to breadth, i : 1.07. Regions scarcely distinct. Lat- 

 eral margin with two or three equidistant inconspicuous angles, bet- 

 ter marked in the female than in the male, but seldom dentigerous. 

 Posterior margin straight or slightly convex. The sharp margins 



