ix, d, 4 Cowles: Palaemons of the Philippine Islands 341 



Palaemon philippinensis seems to be most nearly related to 

 P. nipponensis de Haan, 23 differing from this species in size, in 

 the absence of the rather thick coating of hairs on the fingers, 

 and in the presence of distinct tubercles along the sides of the 

 cutting edge. The tubercles (absent in young males, in most 

 "males feminises," and in all females but the largest specimen) 

 remind one of P. elegans de Man 24 and P. rudis Heller, 25 but 

 in Palaemon philippinensis the tubercles are found on both sides 

 of the cutting edge of the mobile finger and only on one side, 

 the inner, of the cutting edge of the immobile finger. 



Two other striking characteristics of this species are the 

 variability in the shape of the rostrum, reminding one of 

 P. weberi de Man, and the variability in proportion between 

 the lengths of the carpus and merus, which also seems to be 

 characteristic of P. ritsemae de Man 26 and P. rudis Heller. 

 These variations, together with the occurrence in the collection 

 of both forms of the male, would have aroused a doubt in my 

 mind as to the specimens being of one species if I had not seen 

 them all shortly after they were taken from the water, when 

 the living color was still retained and when they showed a 

 characteristic T-shaped pigment mark and certain "obliquely 

 placed pigment marks on each side of the carapace, which are 

 found in no other species in our collection. (See discussion on 

 the color of P. philippinensis.) 



The following is a description of the largest male specimen in 

 the collection (one from San Juan River near Manila), after 

 which follows a comparative description of specimens differing 

 in age and sex : 



This male (Table II, specimen 31) (Plate II, figs. 2, 2a, 2b, 

 and 2c) measures 144 millimeters in length. The rostrum fails 

 to reach the tip of the antennal scale. The dorsal border is 

 conspicuously convex over the eye, the ventral border curves 

 upward moderately, but the tip is not directed upward. The 

 ridge along the side of the rostrum divides the surface of the 

 latter into an upper wide and a lower narrow area. Along the 

 dorsal border are 12 teeth, the first, second, and third of which 

 are situated on the carapace. These are separated by wider 

 intervals than those immediately following. The ninth and 

 eleventh teeth are also farther apart than those immediately 



w Fauna Japonica. Siebold (1833), 1, 171. 



84 Zoologische Ergebnisse einer Reise in Niederlandisch Ost-Indien (1892), 

 2, 440. 



"Reise der Osterreichischen Frigatte Novara (1868), 2, 115. 

 "Zool. Jahrb., Systematik (1897), 9, 774. 



