474 BULLETIN 152, TTNITED STATES NATIONAL MUSEUM 



widest part of the mesogastric region. Anterior part of this region 

 outlined; crescentic grooves at middle of carapace well marked. 

 Each lobe of front is oblique and subdivided into three, one large 

 submedian and two small. Inner supraorbital tooth with transverse 

 anterior margin; outer angle obtuse, not advanced; lower margin 

 bidentate, inner tooth prominent, outer one lower than the inner, 

 but similar to and almost merged with the tooth above it, but more 

 advanced. Second to fourth lateral teeth shallow, more or less trun- 

 cate or lobiform, having short anterior and long posterior margins, 

 which meet at an obtuse angle. Fourth tooth subdentiform, last 

 tooth dentiform, blunt, projecting outward; from it a low, blunt ridge 

 runs obliquely backward. 



Dactylus of major chela with a large basal tooth, fixed finger with 

 a large subbasal tooth; other teeth few and large. The fingers of the 

 minor chela have numerous small teeth. The dark color of the fin- 

 gers ends in an uneven or broken, oblique Hne, the color extending 

 the length of the prehensile edge but little more than half the length 

 of the outer edge. On the distal upper half of the inner surface of 

 both palms in both male and female there is a broad oblong patch 

 of striae obliquely placed, which serves as a stridulating organ. It is 

 adapted for playing against the thick edge of the second and third 

 antero-lateral teeth and the outer suborbital tooth. There is a series 

 of granules on the suborbital and subhepatic regions which may pro- 

 vide the element of friction, although the articulation of the arm 

 seems not to permit this. There is a row of these round or oblong 

 granules or small tubercles behind and parallel to the lower orbital 

 border, and on the second and third antero-lateral lobes, besides a 

 few granules toward the buccal cavity. 



Color. — Young specimens, a dark purplish blue, the very young 

 always with a white spot on the wrist; with age the color becomes a 

 dark brownish red more or less mottled and spotted with dusky 

 gray. (Hay.) Fingers black; legs ornamented with red and yellow 

 bands. 



Measurements. — Male (32250), total length of carapace 85.6, width 

 of same 127, fronto-orbital width 47, width of front 24.6 mm. 



Habitat. — The young are hatched at intervals throughout the 

 spring and summer and, after having assumed the crab form, appear 

 to resort to the deeper channels of the harbor where they live under 

 the shell fragments with which such bottoms are covered. On at- 

 taining a width of half an inch or thereabouts they move into shal- 

 lower water and may be found among the oyster shells and the rocks 

 about the harbor jetties. Here they live until they have attained 

 full size, when, if circumstances seem to demand it, they move to 

 some shoal and just below low-tide mark make burrows. These 



