39 



the distal extremity, is 2,6 mm. long, 0,34 mm. broad near the base and 0,27 mm. in the 

 middle, being almost lo-times as long as broad in the middle, the slightly curved and tapering 

 dactylus, finally, is 1,35 mm. long. The relative measurements of the 3'''^ leg are therefore: 

 merus 2,2, carpus i, propodus 1,44, dactylus 0,75. 



The 4''' leg of the male presents the following measurements. Merus 3,1 mm. long, 

 0,42 mm', broad, 7,4-times as long as broad; car])us 1,65 mm. long, 5-times as long as thick 

 at the distal extremity; propodus 2,4 mm. long, 0,3 mm. broad near the base, 0,24 mm. in 

 the middle, lo-times as long as broad in the middle; dactylus lost. The relative measurements 

 are: merus 1,9, carpus i, propodus 1,45. The merus of the 4''' leg of the female, finally, 

 2,7 mm. long and 0,4 mm. broad, is 6,75-times as long as broad; carpus 1,5 mm. long, 5-times 

 as long as thick at the distal extremity; propodus 2,12 mm. long, dactylus 1,12 mm. and the 

 relative measurements are here: merus 1,8, carpus i, propodus 1,4, dactylus 0,75. 



The appendix masculina of the 2"^' pleopod of the male measures one-fourth the length 

 of the endopodite and is implanted just behind the middle of the latter; it bears anteriorly 

 and on the tip about a dozen of setae; the naked and glabrous stylamblys looks like a ribbon. 



Alpheiis tenuicarp2is de Man differs at first sight by the deep emarginations, by 

 which the orbital hoods are separated from the rostrum, by the antennal peduncle projecting 

 by the length of 3'''' article beyond that of the upper antennae, by the larger chela of 

 the male being about 3-times as long as high and by some slight differences in the measure- 

 ments of the following peraeopods. 



Alpheits iejtuipes de Man from the northern entrance of Buton-strait is also closely 

 related, but easily distinguished by the different form of the telson, which is more narrowed 

 posteriorly, with smaller dorso-lateral spinules and the posterior margin of which is 

 truncated, not at all projecting backward; the rostral carina is separated by feeble 

 depressions from the orbital hoods, the stylocerite is as long as basal antennular article and 

 the peraeopods of the 3'''^ pair are still more slender. 



Alpheus rapacida de Man, finally, differs by the rostral carina which can be followed 

 almost t o the middle of the carapace, by the less slender shape of the peraeopods 



and by some other characters. 



t 



Measurements in millimeter s. 



Length of the telson , 



Width at the base 



Width of the posterior margin 



Length of the posterior margin in the middle line 



Proportion between the length of the telson and the distance of the an- 

 terior pair of dorso-lateral spinules from the posterior margin 



Proportion between the distances of both pairs of spinules from the 

 posterior margin 



Proportion between liie length of the telson and the width of the poste- 

 rior margin 



Proportion between the width at the base and that of the posterior margin 



N". I male from Stat. 51, N". 2 female from Ambon. 



