142 Bulletin Vanderbilt Marine Museum, Vol, VI 



The external maxillipeds are pediform, slender, with the dis- 

 tal article bearing black-tipped spines and extending almost to the 

 tip of the antennal peduncle. 



Discussion : The present species, which is closely related to 

 A. macroskeles Alcock and Anderson, and also to A. talismani 

 Coutiere, differs from macroskeles as figured by Coutiere, in that 

 the present species has the antennular peduncle longer by the 

 third article than the inner portion of the scaphocerite, while 

 macroskeles has these two subequal in length. The stylocerite of 

 explorator is distinctly shorter in ratio to the related first anten- 

 nular joint and is also broader, or wider, with the lateral margins 

 more convex than in macroskeles; the apical spine of explorator 

 is acute, but is more decisively set apart from the convex proxi- 

 mal portion of the stylocerite than is that of either talismani or 

 macroskeles. The rostrum of the present species has about the 

 same length ratio to the first antennular peduncle joint as in the 

 two other species, but is distinctive in that it continues posteriorly 

 as a distinct carina for a little more than half the length of the 

 carapace. The great cheliped resembles that of talismani in its 

 much attenuated slenderness, but differs in having the fixed finger 

 of explorator bent inward at a decided angle, in having this finger 

 a little longer in ratio to the palm and in having the upper finger 

 shorter in relation to the fixed finger. 



Dr. Alcock stated of macroskeles that "the eyes are markedly 

 deficient in pigment"; but explorator has fairly large, well- 

 developed ocular areas visible dorsally as circular spots and also 

 visible slightly as black ocular lobes protruding on the frontal 

 region slightly beyond the carapace. 



Brevirostris Group, ss. Coutiere 

 Alpheus rapax Fabricius 



Plate 37 



Type : Fabricius' type came from the East Indies and, if still 

 extant, is very probably in the British Museum. 



Distribution: Red Sea, Djibouti (Coutiere); Massaouah 

 (Nobili) ; King Island, Mergui Archipelago (de Man) ; Hulule, 

 Male Atoll, Maldives (Coutiere) ; Sagarai Bay, Japan (Doflein) ; 

 Zanzibar (Hilgendorf). 



