26 



£ii?. Ramnee, Garwhal. Museum Collector. 6 c? , 1 9- 



10 



5450 



Nepal Terai. Mascmii Collector. 1 cJ. 



?1IM^. Bhini Tal, Kumaon, i500 feet. N. Annandale. 15 J, 17?. 



10 



•^•^^^ Naiiii T.U District. Museum Collector. 1 t?. 



10 



51^. Hazara, United Provinces. Museum Collector. 2 <5 , 1 9 . 



10 



5i^. NainiTal. Purchased. 1 c? . 



10 



ool6 jj jj^^.j (-|,^.j„^j,.^ Captain Murray. 1 (?, 1 ?. 



10 



The egcrs of P. koolooense, though large — about 2*5 mm. in diameter— are 



numerous. 



5. PoTAMON (Potamon) atkinsonianum, Wood-Masoii. (Fig. 39.) 



Ti-lphnxa alkiiisoniana, Wood-Mason, Journ. Asiatic Soc, Bengal, XL.. 1871, pt. I., p. 205, pi. xiv., figs. 12-16. 

 Potamon (Potamon) atkinaonianns, Mary J. Rathbun, Nouv. Archiv. du Museum, Paris (4), V'l.. 1904, 

 p. 271 {ubi lit.). 



This species resembles all the preceding in having the merus of the 

 external maxillipeds broader than long. 



From P. fluviatile and its varieties it differs in the following particulars : — 



(1) The carapace is broader, its length being only three-fourths its greatest 

 breadth, and behind the frontal declivity it is quite flat in both dimensions ; 



(2) The front is narrower, being considerably less than one-third the 

 greatest breadth of the carapace in the adult ; it is also less distinctly bilobed ; 



(3) The cervical groove is particularly deep-cut, and the epibranchial 

 regions are very distinctly areolated ; 



(4) The epigastric and post-orbital crests, though distinctly separated from 

 one another, form one curve, the general trend of which is gently convex 

 forwards ; 



(5) The chelipeds are more boldly sculptured. 



From P. koolooense it is distinguished by the following characters : — 



(1) It attains a larger size ; 



(2) The carapace is flatter, with a deeper-cut cervical groove and more 

 distinct areolation of the epibranchial regions ; 



(3) The epigastric and post-orbital crests form one curve ; but this is 

 sometimes the case in P. koolooense. 



It must be admitted, however, that P. atkinsonianum and P. koolooense 

 may probably be the extremes of one variable series, and so " species " only in a 

 conventional sense, in so far as the extremes of the series can be defined; As 



