152 ZOOLOGISCHE MEDEDEELTNGEN — DEEL I. 



M. polleni = latreillei. 

 „ serratus = M. latreillei. 

 „ simplicipes = M. pectinipes. 

 „ verreauxi — M. telescopicus. l ) 



So there remain 25 names referring to well defined species and marked 

 with an asterisk in the complete list of names. 



The following key may serve in distinguishing these species 2 ) : 



1. Carapace with large spinous tubercles, conspicuously visible to 

 the naked eye ; posterior margin of propodites of walking legs in the 

 penultimate pair with a row of large, curved spines. M. pectinipes. 



Carapace differently shaped, either transversely broadened and con- 

 spicuously twice as broad as long, or more or less subquadrangular, but 

 always smooth or with rounded obtuse tubercles ; walking legs mostly 

 hairy or smooth, but not spinous at the propodites. 2. 



2. Ocular peduncles much elongated, projecting more or less far beyond 

 the external orbital angle. 3. 



Ocular peduncles shorter, in extreme cases reaching a little way 

 beyond the external orbital angle (only for the length of the corneae). 5. 



3. Length of carapace to breadth about as 1 : 1.60, smooth; eye-stalks pro- 

 jecting beyond the external orbital angle for about half their length. 4. 



Length of carapace to breadth about as 1 : 2.40, with very declivous 

 branchial regions and a longitudinal row consisting of 3 — 4 denticu- 

 lated tubercles on these regions; eye-stalks projecting for a third of 

 their length beyond the external orbital angle. M. transversus. 



4. The two last joints of the hinder pair of legs flattened, penultimate 

 joint nearly circular. 31. latipes. 



The two last joints of the hinder pair of legs not differing from 

 the joints of the foregoing legs. M. télescopions. 



5. Carapace nearly exactly twice as broad as long, sometimes even broad- 

 er; outer surface of the palm of the male cheliped with an elevated 

 rim running close to and parallel with the under margin (sometimes 

 modified into a row of small granules). 6. 



Carapace more subquadrangular and always less than twice as broad 

 as long, palm of the male cheliped nearly smooth, mostly without rim, 

 which may be however faintly visible on the immovable finger. 13. 



1) This list does not agree in several respects, as I am fully aware, with long accepted 

 views of former authors, but I shall have occasion to sustain my opinion in discussing the 

 various species. 



2) I do not consider the species provided with a musical crest in the male ses a natural 

 group within the genus, as Ortmann seems inclined to do (Zool. Jahrb. Abt. Syst., Bnd. 10, 1897, 

 p. 340) and consequently I have not separated those species from the rest. 



