90 CARCINOLOGICAL STUDIES. 



larger and stouter thau in the two lastnamed species. The 

 anterior margin of the epistoma is divided in Plag. immacu- 

 lata as well as in Plag. speciosa into three lobes, of which 

 the middle one is much smaller than the two lateral ones. 

 The two lateral lobes present three (or more) secondary 

 lobes in the former species, but I observe in those of the 

 male specimen of Plag. speciosa only one single small in- 

 cision , and in the female the lateral lobes are even entire. 

 The inferior margin of the orbits , on the contrary, appears 

 entire in Plag. immaculata , but in Plag. speciosa this 

 margin presents a larger emargination near the internal 

 angle and several smaller ones between this incision and 

 the external angle, so that the margin appears irregularly 

 denticulate or lobate. 



The third , fourth , fifth and sixth segment of the abdo- 

 men of the male are coalescent; the abdomen is smooth, 

 and marked with some faintly impressed trans- 

 verse lines. The segments of the sternum bear also a 

 few impressed lines, of which those of the anterior 

 segment are for a part fringed by short stiif hairs. In the 

 female the third, fourth and fifth segment are coalescent and 

 here the abdomen is also ornamented with a number 

 of transverse and symmetrical impressed lines, 

 each of which is bordered by a fringe of short stiff hairs. 

 The sternum and the abdomen of the male of Plag. imma- 

 culata , however, present no impressed lines , and the fourth , 

 fifth and sixth segment only seem to be coherent; the 

 abdomen of the female of that species is seven-jointed and 

 also smooth. 



The hands are stouter, more robust and co m- 

 paratively higher than those of Plag. immaculata. 

 Those of the male are about once and a half, those of 

 the female scarcely twice as long as high ; the hands of 

 Plag. immaculata are comparatively less high and there- 

 fore more slender. The hands of Dana's species present 

 a greater resemblance to the form we observe in the 

 species of the genus Grapsus. The convex outer surface of 



Notes from tlie J-ieyden JMuseum, Vol. XII. 



