80 CRUSTACEANS OF THE 



Potamon {Perithelphusa) Biittikoferi, n. sp. 



(Plate 6, fig. 5). 



Four males of difi'erent size from Sintang, collected by 

 Max Moret. 



This new species bears some resemblance to the prece- 

 ding one: the meropodites of the ambulatory legs present 

 a spine on their anterior margin and the upper angle of 

 the arm of the chelipedes also, the abdomen has about 

 the same form and as regards the postfrontal ridge , as 

 little defined , both species agree with one another. There- 

 fore this species, that I have the pleasure to dedicate to 

 the Zoologist of the Expedition, may be likewise referred to 

 Perithelphusa. The second male has- been compared by 

 Prof. Hilgendorf with the type of Potamon horneense v. Mart, 

 and he wrote me that he considered this species to be new. 



As in Pot. horneeyise v. Mart. var. hilaris, the greatest 

 width of the cephalothorax is in proportion to its length 

 as 4:3, but the distance between the epibran- 

 chial teeth and also that between the outer 

 orbital angles are in proportion to the great- 

 est width a little shorter and as the lateral 

 margins have a different form and direction, 

 the cephalothorax of both species presents a 

 different shape and figure. 



As regards the convexity of the carapace, as well from 

 end to end as from side to side, both species almost agree 

 with one another; in the largest specimen the gastric 

 region appears slightly less convex transversely but this 

 may be an individual difference. Concerning the little deve- 

 lopment or rather absence of a post-frontal ridge, both 

 also agree with one another; it is only indicated by the 

 slope, by means of which the gastric region subsides to- 

 wards the front and towards the post-frontal furrow. The 

 epigastric lobes are slightly advanced, wrinkled anteriorly, 

 not limited off posteriorly, but continuous with the gastric 



T^otes from the Leyden JMuseucn, Vol. XXI. 



