176 ZOOLOGISCHE MEDEDEELINGEN — DEEL I. 



1897. M. graeffei Ortmann. Zool. Jahrb. Abt. Syst., Bnd. 10 p. 343 (no 



new record). 

 1900. „ convexus Alcock. Journ. As. Soc. Bengal, v. 69 prt. 2. p. 378 



(Andamans). 

 1902. „ convexus de Man. Abhandl. Senckenb. Gresellsch., Bnd. 25 p. 493, 



pi. 19 f. 6 — 6a (Ternate and Halmaheira). 



1906. „ inermis Rathbun. Buil. ü. S. Fish Comm. v. 23, prt. 3, p. 834, 



(Hawaiian Islands). 



1907. „ convexus Stimpson. Smithson. Inst., Miscell. Coll., v. 49 p. 97 



pi. 13 f. 2 (Loo-Choo-isles). 

 1910. „ convexus Rathbun. K. Dansk. Yid. Selsk. Skr., 7. Raekke, v. 4 

 p. 323, pi. 2 f. 3 (Gulf of Siam). 



Miers already advanced that M. inermis of Milne-Edwards might be 

 identical with Stimpson's M. convexus, and this has been confirmed by 

 de Man (1888), who could study the type-specimens of M. inermis. 



I think that the M. graeffei is founded on a very young male spe- 

 cimen *) of the species now under discussion. Indeed 31. graeffei shows 

 exactly the same shape of the lateral teeth and notably the external 

 orbital angle is sharp and pointed, directed obliquely forward and much 

 larger than the lateral teeth, the curve of the upper orbital border is 

 also alike and the ocular peduncles project slightly beyond the sides of 

 the carapace; the latter is stated by Milne-Edwards to be „dépourvue 

 de granulations ou de tubercules, à peine piquetée sur les régions bran- 

 chiales". In this young specimen I presume that the verrucous tubercles 

 on the branchial regions are not yet fully developed. Moreover the chela 

 of M. graeffei is covered with hairs only at the inner side of the fingers, 

 whereas the inner surface of the palm is naked, quite as in Milne-Edwards' 

 figure of the adult chela of n M. inermis" in the Nou v. Arch. t. 9, pi. 12 f. 5 a . 



In all the species as yet treated of, the external orbital angle is 

 either smaller than the anterior lateral tooth of the carapace or these 

 teeth are alike in size. The only exception is formed by M. telescopicus 

 with its long ocular peduncles. In M. convexus the external orbital angle 

 on the contrary is much larger than the anterior lateral tooth, it is 

 directed obliquely forward in such a way, that the tip (in adult specimens 

 at least) may be on the same level with the upper orbital border 2 ). By 



1) According to Milue-Edwards the breadth of the carapace is 14 mm., the length 7 mm.; 

 in his figure 5 a , where the dimensions of the carapace are given in natural size, these dimensions 

 are much less (breadth 8 mm., length 5.5 mm.). There must be an error either in the text or 

 in the figure. 



2) In Stimpson's figure (1907) however the upper orbital border projects much farther forward 

 than the outer orbital ande. 



