DECArOU CRUSTACEA FROM MADAGASCAR. 929 



The material which I have examined consists of eleven speci- 

 mens, from three localities, in the British Museum (Nat. Hist.) Col- 

 lection and nineteen specimens from one locality in Mr. Methuen's 

 collection. The Museum specimens (PI. XCII. fig. 1) agree witli 

 Hilgendoi-f's description of this species, except in one or two small 

 details to be mentioned below. Mr. Methuen's specimens were at 

 first regarded as repi-esenting a probably new species of Palaimon^ 

 since they possess a well-developed hepatic spine on the carapace 

 (PJ. XCII. fig. 6). Closer examination showed, however, that 

 they differed in no other respect from the Museum specimens, 

 and their specific identity was finally proved by the discovery, 

 among Mr. Methuen's specimens, of one which has no trace of a 

 hepatic spine on one side of the carapace, while on the other 

 side its place is indicated by a small and inconspicuons tubercle. 



The following description applies to all the specimens examined. 



The sides of the carapace and the abdominal somites are 

 rather coarsely punctate. The rostrum is moi'e or less straight, 

 with the dorsal edge moderately arched, of varying length but 

 always shorter than the antennal scale, and often shorter than 

 the antennular peduncle ; of the dorsal teeth, one is postorbital. 



The tip of the telson (PI. XCII. figs. 4 & 5) is rather broadly 

 rounded, sometimes, but not always, with a minute median point ; 

 the inner lateral spines are much longer than the outer. Between 

 the inner spines is a fringe of sixteen plumose haii'S. 



The third maxilliped does not reach the tip of the antennal 

 scale. The chelipeds of the first pair extend beyond the scale by 

 a little more than the chela. 



The chelipeds of the second pair (PI. XCII. fig. 2) are similar, 

 smooth, with fine scattered setules, and may extend beyond the 

 antennal scale by the length of the chela and carpus. The carpus 

 is equal to the merus, widened distally ; the chela slightly com- 

 pressed (5 : 6), a little wider than distal end of carpus ; palm 

 longer than car-pus and equal to fingers ; fingers with a shai'p 

 cutting-edge for the greater part of their length, with two small 

 teeth near the base of the dactylus, and one, with an indistinct 

 second, on the immovable finger (PL XCII. fig 3). 



Posterior legs moderately stout, propodusof last pair about twelve 

 times as long as wide and about four times as long as the dactylus. 



The females are ovigerous from a length of about 38 mm. 

 upwards. The eggs measure approximately 2 X 1"4 mm. 



It will be observed, from the table of measurements given 

 below, that the females ai-e much more numerous than the males 

 in the collections examined and also that they considerably exceed 

 them in size ; both conditions appear to be uncommon among the 

 species of Palcemon, but they are found also in P. inoorei of Lake 

 Tanganyika. 



Hilgendorf described the mandibular palp as consisting of only 

 two segments. In all the specimens which I have dissected the 

 usual three segments are distinct. Hilgendorf also attributes 

 three. teeth to the dti.ct^dus of the second chelipeds and states that 



