ix, d, 4 Cowles: Palaemons of the Philippine Islands 349 



females become more nearly mature there is an increase in the 

 distance between the longitudinal ridge on the side of the rostrum 

 and the dorsal border. At the same time there is a decrease 

 in the relative length of the rostrum, so that the rostrum of 

 younger individuals is a rather narrow blade while that of the 

 older individuals is a broader blade. 



The dental formula for the males (33.5 to 144 millimeters) is 

 11, 12, 13 

 % 3, 4, 5 



, while that for the few females in our collection is, 



with one exception, — ' ' — . As in the local form of Palaemon 



carcinus, there is no evidence that the number of teeth on the 



rostrum increases with age. It should be mentioned that the 



exception referred to above is a female 93 millimeters long, in 



18 

 which the rostral formula is -=- (Table II). This specimen has 



recently carried eggs, and has a rostrum similar in shape to 

 the largest males. The living color markings agreed exactly 

 with those of other females of this species. The chelipeds, in 

 shape, armature, and proportion, are much like the chelipeds 

 of specimen 37 (97 millimeters) indicated in Table II. I have 

 hesitated before diagnosing this individual as P. philippinensis, 

 but as I can find no character which would rule out the specimen, 

 except the large number of teeth on the dorsal border, I am 

 forced to include it. In young and middle-aged males the teeth 

 9 and 10, or 10 and 11, or 11 and 12, or 12 and 13 on the dorsal 

 border of the rostrum are more widely separated from one 

 another than those farther back. The comparatively wide space 

 between any two or any three of the teeth just mentioned is very 

 evident in the young, but it decreases gradually as the animal 

 grows larger, until in the largest males these teeth are almost 

 evenly spaced. Similar prominent spaces are seen on the young, 

 middle-aged, and older females. The first, second, and third 

 teeth are usually found on the carapace in both males and females, 

 although occasionally the third is astride of the edge of the orbit. 

 The distance between the first and second and usually also between 

 the second and third is greater than that between the teeth 

 immediately succeeding. The lower border of the rostrum in 

 both sexes and at all ages curves upward in its distal two-thirds, 

 but this upward curving is not so pronounced in old age. The 

 most distal tooth of the lower border is almost invariably at a 

 considerable distance from the tip of the rostrum. 



