926 un. w. T. f^ALMAis' ox 



While all the adult males and a good many of the females in 

 the collection have been referred, to one or other of these species, 

 there remain over a number of specimens which either lack the 

 large chelipeds or are clearly immature. It is possible that these 

 may include representatives of some other species, but I have not 

 succeeded in identifying them, and it does not seem that any 

 good purpose would be served by enumerating them here. 



The most interesting species in the collection is that which I 

 identify with Bithynis hildebrandti of Hilgendorf, which does not 

 appear to have been re-examined since its description in 1897. 

 The series of specimens collected by Mr. Methuen, together with 

 those already in the Museum Collection, show, I think, that this 

 species is not closely related to the Chilian species which is the 

 genotype of Bithynis ; that the single character which led to its 

 being referred to the genus Bithynis is a matter of individual 

 variation ; and that, therefore, the species should be removed to 

 the genus Falcemon. 



Pal^^mon (Macrobrachium) lepidactylus Hilgendorf. 



Palcemon lepidactyhos Hilgendorf, Monatsber. Akad . Wiss. Bei-lin, 

 1878 (1879), p. 838, pi. iv.'figs. 14-16. 



Palcemon {Macrohrachmm) lepidactylus Couti^i'e, Ann. Sci. Nat. 

 Zool. (8) xii. 1900, p. 272, pis. x., xi. figs. 1-13 a. 



Localities. Arabatonharanana, 7 males (^Methuen) ; Rapides de 

 ITfotry, 1 male (Methuen): Betsileo, 3 males, B.M. 80.27. 



In the characters of the rostrum and of the larger cheliped all 

 the specimens fall within the range of vai'iation determined for 

 this species by Coutiere. In no case, however, does the form of 

 the smaller cheliped agree with that which he regards as typical. 

 The fingers of this appendage are in all the specimens straight or 

 nearly so, meeting completely or with only a slight gap, and 

 having a scanty pi'ovision of bristles on their opposed edges. In 

 these respects the specimens agree much better with Couti^i-e's 

 B. hilgendorfi, a.nd suggest that that species should not be 

 i-egarded as distinct from P. lepidactylus. 



Pal.emox (Parapal^mon) DOLicHODACTYLUS Hilgendorf. 



Palcemon dolichodactylus Hilgendorf, Monatsber. Akad. Wiss. 

 Berlin, 1878 (1879), p. 840, pi. iv. fig. 18. 



Palcemon dolickodactyhis Coutiere. Ann. Sci. Nat. Zool. (8) xii. 

 1900, p. 283, pi. xi. %s. 18, 19. 



Localities. Andraiiolaho and Tongoroby, Onilahy River, 15 

 males, 3 females [Methuen). 



The larger males in the collection agree very well with the 

 accounts of tins well-marked species given by Hilgendorf and by 

 Coutiere. With them are associated some smaller specimens in 

 which the w^oolly covering of the larger chela is very slightly 

 developed. The rosti^al formula is -~£, with 4-5 of the upper 

 teeth postoibital. 



