CANCROIDEA. 253 



The same species varies much in the dentation of the arm, even 

 the right and left arm being often much unlike. Moreover the spine 

 of the lateral margin, and that of the inner margin of the carpus, 

 may become blunt, or almost disappear with age. It is, therefore, 

 exceedingly difficult to determine how far these points may afford 

 specific characters. The colour is various among the species, and 

 seemingly important; yet we have been unable to test this impor- 

 tance, since specimens differing decidedly in style of colouring, are 

 apparently identical in their other characters. Riippell* considers 

 the colour as a specific distinction, and has named several species on 

 this ground, not mentioning other characters. 



The character of the tarsus is cjuite peculiar, as shown in our figures. 

 The extremity is an oblong process with a blunt apex, filled and not 

 hollow. The upper margin of the apex is set with exceedingly short 

 spines, blunt at the point, and other longer spines and hairs are 

 situated as shown in the figures referred to. The pterygostomian 

 region is crossed by a raised line, which begins either side of the buccal 

 area, near its posterior part (fig. 5 d) . 



The species, as well as the Tetraliae, are found among the closely 

 entangled branches or folia of living corals, and are very common in 

 the tropics. 



Grapsillus, of M'Leay (Smith's Tllust. S. Af., Annulosa, p. 67), is identical with Tra- 

 pezia of Latreille, as remarked by Krauss (loc. cit., p. 35). 



1. Later a cara/pacis inermia. 



Trapezia speciosa. 



Frons fere integer, versus oculos et ad medium obsolete^ emarginatus. 

 Pedes antici subaiqui, carpo supra obtuso, articulo tertio apicem inter- 

 num acuto (rectangulato) et marginem internum denticulato, denticidw 

 subquadratis, minutis. Pedes 8 postici toti tenues, coxis articulisque 

 sequentibus perangustis, subcylindricis. 



Front very nearly entire, obsoletely emarginate at middle and also 



* Krabben des rothen Meeres, Frankfurt, 1830, p. 27. 

 64 



