98 



of the second thoracic pair arc somewhat unequal, but in nil of them 

 the fingers are nearly as long as the palmary portion of the hand, thus 

 differing from the P. brachydactylus of Wiegmann. 



JPalcemon tenellus, sp. nov. Male. Rostrum very long, reaching far 

 in advance of the tips of the antennal scales, the basal half high, 

 curved somewhat downward, then beyond the middle curved strongly 

 upward, and tapering to a slender extremity; the upper edge armed 

 with eight to ten teeth, of which seven or eight are on the basal half 

 and the others near the tip, and the under edge with six or seven teeth. 

 Second thoracic legs slender and nearly smooth, except the fingers, 

 which are straight, slender, somewhat hairy, and not quite as long 

 as the palmary portion of the hand. Fifth segment of the abdomen 

 projecting into a sharp point at the posterior lateral angle. Sixth 

 segment less than a third longer than broad; the lamellae rather 

 narrow and evenly rounded at the extremities. Tei'minal segment 

 narrow and tapering to a triangular tip armed with small spines. 

 Length of body from tip of rostrum to extremity of abdomen, 96 mm ; 

 length of carapax from orbit to middle of posterior margin, 23.1 ; 

 length of rostrum, 23.9. Another specimen gives : Length of body, 

 83 mm ; carapax, 18.7; rostrum, 20.0; second thoracic legs, 41.0; merus 

 in second thoracic legs, 9.1 ; carpus, 12.1; hand, 10.5; dactylus, 4.8. 



Polvon, Occidental Department of Nicaragua. 



Both of the second thoracic legs are preserved in no one of the 

 specimens, and those which are present seem very small and may have 

 been reproduced. This species is very much like P. Amazonicus 

 Heller, Sitzungsberichte der kaiser. Akacl. der "Wissenschaften, Wien, 

 xlv, p. 418, pi. 2, fig. 45, 1862 (which is the same as P. ensiciclas Smith, 

 Trans. Conn. Acad., vol. ii, p. 26, pi. 1, fig. 2, 1869), but is at once 

 distinguished from it by the terminal segment of the abdomen, which 

 has a triangular and spinous tip, instead of terminating in a very 

 slender and acute point; the sixth segment also is not nearly so 

 narrow, and its lamella? are not so long and slender. 



