vew C rah from the Indian Ocean. 31 



side. Abdomen o£ male with seven segments distinct, the 

 third to fifth more firmly connected than the others. 



Type species, Calocarcinus africanns, sp. n. 



This genus approaches closely to Sjjhenomerides, Rathbun 

 {Sphenomerus, Wood-Mason), though differing from it in 

 several important characters. In having the orbital gap 

 completely closed it agrees with the more typical Trapeziinse, 

 but in the general shape of the carapace, and especiallyin 

 the relative narrowness of the frontal region, it differs from 

 these and from all the related subfamilies, and assumes more 

 the typical Xanthine aspect. On comparing the species 

 described below with Sphenomerides trapezioides, W.-M.*, 

 and with a Trapezia, it is impossible to doubt that all three 

 are closely related, although Sphenomerides is excluded by 

 its open orbital gap and Calocarcinus by its narrow front from 

 current definitions of the Trapeziinas. It is very easy to 

 point out that the characters hitherto relied on for the sub- 

 division of the Xanthidaa are all of very slight importance, 

 but it is very difficult to suggest any better. Borradaile f 

 has shown that such characters as the "pulley-like" articula- 

 tion of the dactylus of the walking-legs and the closure of 

 the orbital gap, which might be supposed to be of systematic 

 importance, recur in groups apparently unrelated, and Calo- 

 carcinus only adds to evidence already existino- that the 

 general proportions of the carapace are not always trustworthy 

 as a guide to affinity. 



Calocarcinus africanus, sp. n. 



Carapace about three-fourths as long as broad, convex in 

 both directions, smooth and polished, with only slight traces 

 of inter-regional grooves ; octagonal in outline, the antero- 

 lateral margins between the two pairs of antero-lateral teeth 

 being straight and parallel. Fro:it about three-eightlis of 

 greatest width of carapace, with a very shallow median notch 

 and with the supraorbital angles slightly produced, but not 

 acute. There is no tooth at the outer angle of the orbit. 

 Antero-lateral margin straight to the first tooth, the distance 

 being a little more than that between the first and second 

 teeth, which are both blunt. Postero-lateral margin distinctly 

 longer tlian antero-lateral. 



Eyes smaller than in Sphenomerides, nearly concealed 

 when retracted. Antennal flagellum as long as major 



* I am indebted to Dr. N. Annandale, Superintendent of the Indian 

 Museum, Calcutta, for a specimen of this crab. 



t Gardiner's 'Fauna . . . Maldives,' i. p. 239 (1902). 



