336 The Philippine Journal of Science im 



gitudinal grooves, one of which is deep. These divide the 

 surface into 3 regions — 2 lateral and 1 median. Distally the 

 median region of the dorsal surface is highly convex and armed 

 with several stout spines, while the rest of this surface is spine- 

 less. The median region of the ventral surface is smooth. The 

 externolateral region of the ventral surface presents a lon- 

 gitudinal row of fairly stout spines and 2 rows of smaller spines ; 

 the internolateral region of the same surface is armed with 2 

 longitudinal rows of fairly stout spines ; the externolateral region 

 of the dorsal surface presents 2 rows of medium-sized spines; 

 and the internolateral region presents 1 row of fairly stout 

 spines. In younger males and females the more shallow groove 

 mentioned above is absent, so that the same regions cannot be 

 distinguished. The armature and shape remain about the same, 

 except that the spines diminish in size until in the smallest 

 specimens no spines are visible. The ischium grows slower 

 (Table I) than the merus and carpus, a fact which has been 

 noted in the publications of other authors on palaemons in 

 general. 



Third, fourth, and fifth legs. — The third pair of legs in speci- 

 men 2 is absent. The tip of the fourth leg and the dactylus 

 of the fifth leg extend beyond the tip of the antennal scale. 

 The diameter of the propodus of the fifth leg in the middle is 

 0.75 millimeter, and the length is 15 millimeters. In specimen 

 9 the tips of the dactyli of the third, fourth, and fifth legs extend 

 slightly beyond the tip of the antennal scale, and the measure- 

 ments for the propodus of the fifth leg are 1.25 by 25 millimeters. 

 The fifth leg only of specimen 16 is present, and 7 millimeters 

 of its propodus extend beyond the scale. It measures 4 milli- 

 meters in diameter at its middle, and is 61 millimeters long. 



Telson. — The telson of the local form agrees with the de- 

 scriptions and figures which have been published for Palaemon 

 carcinus. The innermost pair of lateroterminal spines on each 

 side of the tip is the largest and best developed. The tip of the 

 telson is acute, and does not extend as far as the posterior border 

 of the uropods. 



Character of surface. — As in many other palaemons, the char- 

 acter of the surface of the carapace and abdomen differs with 

 the age. The carapace and abdomen of males and females from 

 100 to 190 millimeters in length are strikingly smooth to the 

 touch and under magnification show no spines. The third, 

 fourth, and fifth pairs of legs are beset with rows of minute 

 yellowish spinules, especially along their distal two-thirds, but 

 the first pair of legs are devoid of spines of any sort. Males and 



