372 



as in the specimens collected by the "Siboga", the 2 nd is slightly longer than the i st : the 

 carpal segments of the right leg of the female, indeed, measure i,6mm., 1,72 mm., 0,6 mm., 

 0,7 mm. and 0,9 mm., while the chela is 1,36 mm. long (palm 0,54 mm., fingers 0,82 mm.). 



According to H. Milne-Edwards A. bidens should attain a length of 3 inches, while 

 for A. tridentatus the length of 23 mm. is indicated. The specimens collected by the "Siboga" 

 are all of a much smaller size, the largest male and the largest egg-bearing female being 

 23 mm. resp. 23,5 mm. long. The rostrum reaches to the 2 nd thircl part of the 2 nd antennular 

 article, the tooth on the post-rostral carina is small and subacute. Just in front of this tooth 

 one observes at either side an acuminate and pointed tooth, the basal part of which is broad 

 and flattened; these teeth appear more acute and more pointed than in Coutière's figure 57. 

 Orbits prominent, terminating in an obtuse point or tooth, though no spine; between these 

 teeth and the rostrum the frontal margin presents at either side a dentiform, obtuse prominence. 



Basal joint of caudal swimmerets ending in two strong spines, the outer of which is a 

 little longer than the other. 



Second antennular article almost one and a half as long as the visible part of the i st 

 and almost twice as long as thick. So e. g. in the male from Stat. 133, which is 23,5 mm. 

 long, the 2 nd article is 1,1 mm. long and 0,58 mm. thick, while the visible part of i st article 

 is 0,85 mm. long. According to Zehntner the anterior margin of i st antennular article should 

 bear a small spine: in all the specimens captured by the "Siboga" one observes here two 

 small spines placed near one another, which measure one-fourth the length of the 2 nd article 

 and the outer of which is slightly longer than the other; these spines reach almost or just as 

 far forward as the pointed spine in which ends the stylocerite, but sometimes the stylocerite 

 and these spines are slightly shorter. Third article nearly as long as the visible part of the i 5t . 



Antennal peduncle usually reaching to the middle of 3" 1 antennular article, sometimes, 

 as in the egg-bearing female from Stat. 240 and as in the specimen from Stat. 154, only 

 to the end of the 2 nd article. As far as I am aware, the male of A. bidens was still un- 

 known, for Coutière does not mention A. bidens among the species of the Crinitus group, in 

 which the small chela shows the 13 alaeniceps-iovm. (Coutière, 1. c. p. 228). In this species, 

 however, it is really the case. In the male from Stat. 133 the small cheliped is situated at the 

 right side. The upper margin of the merus ends in a strong, spiniform tooth, the two other 

 margins are unarmed. The anterior margin of the carpus bears above two rounded lobes, that 

 are separated by notches from one another and from the contiguous parts of the anterior 

 margin. The chela is turned outward, so that the upper margin is situated externally and the 

 fingers are horizontal; the upper margin of the palm, which is hardly longer than the fingers, 

 is marked with a very short, transverse groove, just behind the articulation of the dactylus 

 and, at either side of the latter, one observes an acute tooth, the tooth at the inner (upper) 

 side being larger than the other. The dactylus shows quite conspicuously the characteristic 

 Balaenicefis-ioxm, the arched upper surface of this finger appears, between the hairy lateral 

 carinae, very obtusely carinate longitudinally. The inner (upper) surface of the chela is covered 

 with long, fine hairs. 



The fingers of the female have the usual slender form and are as long as or a little 



240 



