SPIDER CRABS. RATHBUN. 19 



The basal segment of the antenna has a short, forward- 

 pointing spine at each of the anterior angles, the outer spine 

 more advanced than the inner. Flagellura fringed with long 

 straight hairs. 



The upper margin of the arm is unarmed, the only elevation 

 being a tubercle at the articulation with the wrist. The 

 latter has a strong outer crest, which is entire, and a superior 

 crest which is broken into tubercles ; the two crests converge 

 but do not meet proximally. The movable finger bears a 

 very shallow tooth at its basal third in the gape. The 

 ambulatory legs are covered with hooked hairs and besides 

 there is on each side a fringe of longer, plumose hairs. 



Measurements. Male (P 2134), length of carapace 40.8, 

 width 34 mm. 



Genus LEPTOMITHRAX, Miers. 



Ann. Mag. Nat. Hist. (4), xvii., 1876, p. 20 (type, P. (/,.) 

 longimanus, Miers, 1876, specified by Miers, 1879). 



Orbit fairly complete, the postorbital spine hollowed out to 

 receive the extremity of the eye. 



Key to species in the collection. 



.a. Postorbital lobe or cup truncate and bifid at tip, the two 

 terminal teeth or spines being equally prominent 



b. Two spine sat tip of postorbital lobe. Carapace with 

 many long spines. Four long marginal or sub- 

 marginal spines in a semicircle on the branchial 

 region. Outer maxillipeds swollen at union of 

 merus and ischium. Outer spine of basal segment 

 of antenna less than twice as long as inner spine. 

 Sternal segments not deeply excavate : waitei. 



bb. Two teeth at tip of postorbital lobe. Carapace 

 covered mostly with tubercles. Three long mar- 

 ginal or submarginal spines in a semicircle on the 

 branchial region. Outer maxillipeds not swollen 

 at union of merus and ischium. Outer spine of 

 basal segment of antenna more than twice as long 

 as inner spine. Sternal segments deeply ex- 

 cavate : stern ocostulatus. 



<aa. Postorbital lobe or cup acute, not truncate. There may 

 be a spinule on the outer margin not far behind 

 the tip. 



