24 



The front is less declivous and less distinctly bilobed. 



The epigastric crests are only just in advance of the post-orbital crests. 



The legs are longer, the 2nd (longest) pair surpassing the chelipeds. 



In all these characters it resembles the following species, P. koolooense, 

 Eathbuu ; but it differs from this in its more convex carapace, and (individuals 

 of the same size and sex compared) in its Avider front. 



In the largest specimen — a male which seems to be adult — the carapace is 

 just over Itths of an inch long, and just over liV inch broad. 



Types. 



It is remarkable to find a variety of P. fluviatile so far east, but there is 

 no reason to doubt the labels. 



4. PoTAMON (Potamon) koolooense, Eatlibuu. (Fig. 38.) 



rotamon {Potamoii) kootooemis, Mary J. Rathbun, Nouv. Archiv. du Museum, Paris (4), VI., 1904, p. 270, 

 pi. X., fig. 1. 



This species is distinguished from P. fluviatile, var. ibericum, by the foUow- 

 insr characters : — 



(1) It is a smaller species, egg-laden females sometimes having a carapace 

 less than an inch long ; 



(2) The carapace is broader (its length being only three-fourths of its 

 greatest breadth), flattei', and more roughly rugose antero-laterally ; 



(3) The front is less declivous, is very obscurely bilobed, and is narrower 

 — its breadth being less than one-third that of the carapace in the adult ; 



(4) The cervical groove is deeper cut ; 



(5) The epigastric crests are very slightly in advance of the post-orbital 

 crests — the amount varies. 



(6) The epibranchial tooth is not pre-eminent above the general seri'ation 

 of the antero-lateral borders of the carapace ; 



(7) The legs, even in the adult, are longer in relation to the chelipeds. 

 Carapace : length about ifths the greatest breadth, flat from side to side, 



almost flat fore and aft behind the frontal declivity. Gastric region well 

 defined, the epigastric and mesogastric areolte defined anteriorly, other 

 areolation quite indistinct. Epibranchial regions rather faintly areolated — (1) 

 by a median obliquely transverse depression ; and (2) by extremely faint 

 depressions festooning the gastric region behind the cervical groove. Cervical 

 groove well graven, cutting the post-orbital crests at a point in line with the 

 inner angle of the external orbital spine ; sometimes, behind the spot where it 

 cuts the crests, it appears to give ofi" a branch that runs outside the crest 

 towards the epiliranchial tooth. The greater part of the carapace is smooth, 



