﻿366 The Philippine Journal of Science mi 



which are seen in our specimens of P. lanceifrons, are absent in 

 P. sundaicus. 



Palaemon lanceifrons is not the young of Palaemon philip- 

 pinensis. The latter has differently shaped fingers, there is no 

 thick coating of hair on them, the eggs are much larger, and the 

 color markings are different. 



De Man's 40 suggestion that Palaemon lanceifrons Dana is 

 possibly identical with Palaemon dispar von Martens receives 

 considerable support from my observations. I believe that the 

 former is very closely related to the latter, the only differences 

 being found in the shape of the rostrum, the number of proximal 

 teeth on the fingers, the number of distal tubercles on the fingers, 

 and the shape of the tip of the immobile finger. Further col- 

 lections and an actual comparison of specimens of the two species 

 may show them to be identical. 



There are 9 males and 24 females of this species in the col- 

 lection; they were all purchased in a Manila market. Nearly 

 all the females bear eggs. These measure from 0.5 to 0.7 by 

 0.6 to 0.8 millimeter. 



A local form of Palaemon lanceifrons Dana, collected in San 

 Juan River near Manila, differs slightly from the specimens just 

 described. Except for minor differences, the chelipeds have the 

 same proportions and general characteristics. The rostral for- 

 mula is practically the same, but the rostrum is slightly longer 

 and is less convex over the eye. 



Rostrum and antennal scale. — The rostrum extends about as 

 far forward as the antennal scale, but in some cases fails to 

 reach it or extends beyond it a very short distance. 



Curvature and dental formula of rostrum. — The shape of the 

 rostrum does not vary much, but it must be added that there are 

 not many individuals in the collection and that they do not 

 show a very great range in size. The tip of the rostrum of old 

 and middle-aged specimens turns up slightly, but in the young 

 it is straight. The rostrum usually has its origin rather far 

 forward on the carapace, but in Nos. 5, 7, and 8 (Table IV) 

 it arises from about the middle of the same. Usually, there are 

 2 teeth on the carapace, and the 4 distal teeth at the tip of the 

 rostrum are more widely separated than the rest. The first and 

 second teeth are more widely separated than those immediately 

 anterior to them. The lateral surface of the rostrum is divided 



" Zoologische Ergebnisse einer Reise in Niederlandisch Ost-Indien 

 (1892), 2, 419. 



