y s RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 203 



APPENDIX. 



My paper was already finished and under press, when I became 

 acquinted with Laurie's important treatise on the Brachyura of the Suda- 

 nese Red Sea (Journ. Linn. Soc. London, v. 31 n° 209), published in 

 July of this year. In this paper (p. 470), M. graeffei A. Milne-Edwards 

 is treated of as a distinct species, different from M. convexus. The author 

 states, that in M. graeffei the eye-stalks are longer, reaching slightly 

 beyond the tip of the outer orbital angle, whereas in M. convexus these 

 eye-stalks are shorter, falling short of the outer orbital angle, but in 

 my figure we may observe, that the pigmented region of the eye touches 

 exactly the tip of this outer angle, so that the difference anyhow seems to be 

 not very great. Further there is some slight difference in the shape and 

 the direction of the external orbital angle and the anterolateral teeth of 

 the carapace, which in M. graeffei are more spiniform and more trans- 

 versely disposed than in M. convexus. As to the subterminal spine at the 

 anterior border of the meropodites of the walking legs, such a spine 

 exists in the case of the first to third pairs of these legs in both spe- 

 cies; that such a spine really does exist at the hindermost walking legs 

 is indicated in Stimpson's figure (1907) of M. convexus, but I am inclined 

 to regard this as an aprioristic presumption. The extremely small spine 

 at the meropodites of the first pair of walking legs may easily escape 

 notice, so that Alcock did not mention it. 



Laurie's figures of the cheliped however seem to prove the right of 

 existence of M. graeffei as a distinct species, for even in the larger 

 specimens, of about the same dimensions as the adult M. convexus, the 

 fingers have no larger teeth. 



Moreover Laurie (with Miss Rathbun, 1906) denies the synonymy of 

 M. convexus and M. inermis, on account of the fact, that both Alcock 

 and Stimpson state that the inner surface of the palm of the cheliped of 

 the male is hairy in M. convexus, whereas Milne-Edwards says that this 

 inner surface is naked in M. inermis. I regard this as a difference of 

 little importance, perhaps due to age. It is further true, that Milne- 

 Edwards has not figured subterminal spines on the meropodites of the 

 walking legs of M. inermis ; these spines may have been overlooked, I 

 suppose. For the rest de Man has had occasion to examine typical spe- 

 cimens of M. inermis and declared them to be identical with M. convexus. 



