88 U.S. NATIONAL MUSEUM BULLETIN 292 



Carapace with no more than one spine on anterolateral margin, branchiostegal 

 and rarely antennal spines absent 2 



2. Carapace with hepatic spine on lateral surface; rostrum with ventral teeth; 



eyes not reduced, cornea wider than eyestalk and densely pigmented; 



epigean species 3 



Carapace without hepatic spine; rostrum without ventral teeth; eyes reduced, 

 cornea not pigmented; subterranean species 8 



3. Rostrum long, usually reaching beyond end of antennal scale, with 5-11 



dorsal teeth, no more than 2 of which originate on carapace posterior to 

 level of orbital margin; second pereiopods of adult male slender, chela more 



than eight times as long as broad 4 



Rostrum short, reaching at most slightly beyond end of antennular peduncle, 

 with 10-15 dorsal teeth, at least 4 of which originate on carapace posterior 

 to level of orbital margin; second pereiopods of adult male robust, chela 

 less than seven times as long as broad 5 



4. Rostrum armed throughout dorsal length, posterior tooth usually separated 



from second by distance greater than that between second and third; 

 second pereiopod of adult male spinulose, carpus shorter than chela, fingers 



densely furred Macrobrachium acanthurus (p. 89) 



Rostrum unarmed in distal half or third of dorsal margin except for two sub- 

 apical teeth, proximal teeth subequally spaced; second pereiopod of adult 

 male smooth, carpus longer than chela, fingers bare. 



Macrobrachium jelskil (p. 109) 



5. Rostrum with sinuous dorsal margin, tip slightly upturned; second pereio- 



pods of adult male subequal in form if not in size, with short pubescence 

 and short spines along outer margin of fixed finger and continued onto 

 palm, but spines not forming distinct crest and not hidden by 



pubescence 6 



Rostrum with nearly straight dorsal margin, tip not upturned; second pereio- 

 pods of adult male unequal in both form and size with dense long fur 

 partially concealing crestlike row of long spines on margin of palm . . 7 



6. Posterior teeth of dorsal rostral series not especially erect or noticeably 



more widely spaced than others; second pereiopods of adult male subequal, 

 carpus shorter than merus and about half as long as palm, fingers only 

 slightly shorter than palm, prominent tooth near end of proximal third 

 of opposable margin of fixed finger; abdomen longitudinally striped in 



life Macrobrachium carcinus (p. 93) 



Three or fovir posterior teeth of dorsal rostral series more erect and more 

 widely spaced than anterior ones; second pereiopods of adult male usually 

 unequal in length, major one with carpus about as long as merus and about 

 three-fourths as long as palm, fingers about two-thirds as long as palm, 

 none of teeth on opposable margin of fixed finger greatly enlarged; abdomen 

 transversely banded in life .... Machrobrachium heterochirus (p. 106) 



7. Major second pereiopod of adult male with carpus usually longer than merus 



and fingers distinctly longer than palm, row of spines along mesial margin 

 of palm and fixed finger rather long on proximal portion of palm, becoming 

 shorter near middle of palm, longer near base of finger, and decreasing 



again distally on finger Macrobrachium faustinum (p. 102) 



Major second pereiopod of adult male with carpus shorter than merus and 

 fingers slightly longer or slightly shorter than palm, row of spines along 

 mesial margin of palm and fixed finger forming regular series, not decreasing 

 in length along middle portion of palm. 



Macrobrachium crenulatum (p. 99) 



