10 Annals of the South African Museum. 



\ 



regarded as decidedly longer than the fingers. The transverse 

 granulation along the lower surface of the hand is a very notable 

 character. 



CHAEYBDIS SEXDENTATA (Herbst). 



1783. Cancer sexdentatus, Herbst, Naturg. Krabben u. Krebse, vol. i., 

 pts. 2-5, p. 153, pi. 7, fig. 52 (not pi. 8, fig. 53). 



1798. Portumts annulatus, Fabricius, Supplern. Ent. Syst., p. 364. 



1899. Charybdis (Goniosoma) annulata, Alcock, Journ. Asiat. Soc. 

 Bengal, vol. Ixviii., pt. 2, pp. 49, 54. 



The synonymy of this species, not unattended by doubts, is 

 supplied with Alcock's usual care in the place above cited. But he 

 does not include Talamita sexdentata, Ruppell, Krabben des Eothen 

 Meeres, p. 4 (Thalamita, p. 28), pi. 1, fig. 1, 1830, nor Portunus 

 (Charybdis) 6-dentatus, de Haan, Crust. Japonica, decas secunda, 

 p. 41, pi. 12, fig. 1, 1835. In his key to the Indian species of 

 Charybdis the present species, in common with C. cruciatus, belongs 

 to a group in which " the antennal flagellum is completely excluded 

 from the orbital hiatus ; the ridge that bounds the dorsum of the 

 carapace posteriorly forms a curve with the postero-lateral borders ; 

 no spine on posterior border of arm." Furthermore, these two and 

 some other species have " no distinct transverse ridges on the cara- 

 pace behind the level of the last spine of the antero-latei*al borders," 

 not more than three large spines on the anterior border of the arm ; 

 the orbits have no decided dorsal inclination and their major diameter 

 is never more than one-third the width of the interorbital space. 

 But whereas in C. cruciatus the first spine of the antero-lateral 

 border is anteriorly truncated and notched, in the present species 

 it is acute, and here the sixth pleon segment of the male has the 

 sides parallel, not, as in the other species, convergent. 



From other species with which this is perplexingly surrounded it 

 appears to be sundered by the comparative sharpness of the frontal 

 teeth, the comparative smallness of the last antero-lateral tooth, the 

 character of the last peraeopods, which have the merus or fourth 

 joint nearly twice as long as broad and the hind margin of the 

 propodite or sixth joint serrated in a large part of its extent. The 

 sixth pleon segment is not quite so long as broad. According to 

 Alcock " the major diameter of the orbit is only a fourth the width 

 of the interorbital space." This appears to suit our specimens, but 

 I am not quite clear as to how the measurements are taken. 



The male specimen from the Durban Museum has a carapace 



