380 The Philippine Journal of Science 1914 



Palaemon lar Fabricius. Plate II, figs. 7 and 7a-h. 



The widely distributed Palaemon lar Fabricius is represented 

 in our collection by a large number of specimens, most of which 

 were collected in Mindoro. 



Rostrum and penduncle of the first antenna. — The rostrum in 

 our specimens usually extends to a point slightly beyond or 

 slightly behind the tip of the peduncle of the first antenna, but 

 in one case it reaches to the tip of the antennal scale. In males 

 possessing mature characters (chelipeds longer than the body 

 and fingers gaping widely and with heavy teeth) the rostrum 

 does not extend as far forward with reference to the tip of the 

 antennal scale as in the younger, immature individuals. 



Curvature and dental formula of rostrum. — In the youngest 



specimens the tip of the rostrum is straight and there is almost 



no convexity of the dorsal border of the rostrum, but older 



specimens show a slight upward curve of the tip and a gentle 



convexity over the eye. The first 2 rostral teeth are found on 



the carapace, and usually are separated from one another by 



a greater distance than are those farther forward. Frequently, 



the third tooth lies partly on the carapace. The lateral ridge 



on the rostrum divides the surface into an upper wider and a 



lower narrower region. The number of teeth does not vary 



7 8 

 through a very great range, the dental formula being - ' v . 



Z, o, 4 



First pair of legs. — The whole of the propodus extends beyond 

 the tip of the antennal scale in all the specimens, and in most 

 individuals this distance is increased by from one-fifth to one- 

 third of the carpus. 



Chelipeds. — The chelipeds of immature specimens are approx- 

 imately equal in length except in cases where one cheliped is re- 

 generating. Some of the mature males have chelipeds which are 

 about equal in length, but as a rule there is considerable inequal- 

 ity. Here again, as in many other palaemons, it is impossible 

 to determine from preserved specimens whether the inequality 

 is the result of injury or whether it is a normal, characteristic 

 condition. An interesting case is shown in Plate II, fig. lb, 

 where one of the chelipeds is considerably longer than the other 

 but the palm of the former has a smaller diameter and the fingers 

 are more weakly developed. Our collection does not include 

 the oldest mature males which may attain a body length of almost 

 200 millimeters. Specimens 10 and 13 are young mature males, 

 and their chelipeds are longer than the body. The younger im- 

 mature males, the "males feminises" (No. 12, Table VI), and the 



