's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 153 



6. Inner surface of the palm of the male cheliped with a distinct tooth, 

 placed not far from the proximal end of the palm. 7. 



Inner surface of the palm of the male cheliped without tooth. 12. 



7. External orbital angle and first lateral tooth of the carapace near 

 together and placed crosswise: the longitudinal axis of the orbital 

 angle is placed nearly perpendicularly to the axis of the first lateral 

 tooth, which apparently forms the outer orbital angle. 8. 



External orbital angle and first lateral tooth of the carapace sepa- 

 rated by a distinct incision and both pointing in about the same 

 direction. 9. 



8. Outer orbital angle directed somewhat backward, first lateral tooth 

 pointing transversely; eye-stalks projecting slightly beyond the sides 

 of the carapace. M. sulcatus. 



Outer orbital angle directed transversely outward, first lateral tooth 

 pointing both outward and forward; eye-stalks shorter, scarcely reaching 

 the inner margin of the first lateral tooth. M. grandidieri. 



9. Outer surface of the palm of the male cheliped coarsely granulated 

 in the upper part, median part smooth, under part with a distinct 

 elevated rim, immovable finger without larger tooth on the cutting 

 margin. M. dilatatus. 



Outer surface of the palm of the male cheliped smooth to the 

 naked eye, very finely granulated or punctate when examined with 

 a magnifying glass, under part of the palm with a row of rather 

 large granules that are placed on a more or less distinctly elevated 

 rim; immovable finger with a large, denticulated tooth. 10. 



10. Upper border of the orbital groove very much curved, the top of 

 this curve is in about the same level with the tip of the outer or- 

 bital angle ; palm of the male cheliped very much elongated, its length 

 (without immovable finger) about four times the greatest height. M. brevis. 



Upper border of the orbital groove less curved, sloping, the top of the 

 curve reaching far beyond the tip of the outer orbital angle; palm 

 of the male cheliped short, its length (without immovable finger) only 

 about twice the greatest height. 11. 



11. Upper margin of the palm distinctly serrated, movable finger gra- 

 nulated ; carapace nearly smooth, regularly rounded in a transverse 

 direction, without verrucose tubercles on the branchial regions; 

 first lateral tooth of the carapace larger and projecting farther for- 

 ward than the external orbital angle ; incision between these teeth 

 rather wide. M. hilgendorfi. 



Upper margin of the palm and movable finger smooth; carapace 

 conspicuously granulated, transverse grooves strongly pronounced, 



