98 



Bit. J. &. DE MAK ON A NEW FRESHWATER [Feb. 19, 



rather sharp, curved extremities that cross one another. The 

 dactylus is somewhat granular along the inner border of its upper 

 surface, but for the rest both fingers appear smooth and shining 

 externally ; they are not furrowed, but each finger is marked with 

 two or three longitudinal rows oE small impressed punctures. On 

 the inuer surface, however, the dactylus appears at base dis- 

 tinctly furrowed just beneath the upper margin, but this groove 

 also gradually changes, on the middle of the finger, into a row of 

 punctures ; the immobile finger shows likewise on its inner surface 

 a rather shallow longitudinal furrow that extends almost to the 

 extremity. The dactylus is armed with about 20 or 21 small 

 teeth, the fifth of which is the largest ; the first tooth is but little 

 smaller, the three following gradually decrease in size ; beyond 

 the fifth 15 or 16 very small teeth extend nearly to the pointed 

 tip, two or three of them being a little larger than the remaining. 

 The immobile finger bears also 21 small teeth, the sixth of 

 which is the largest and nearly of the same size as the fifth 

 tooth of the dactylus. The first four gradually increase in size, 

 the fifth is quite small, beyond the sixth there are three or four 

 teeth smaller than the sixth, slightly decreasing in size and sepa- 

 rated from one another by two or three very small teeth. The 

 latter appear on both fingers, are someAvhat compressed, with a 

 straight or slightly arcuate upper edge; the hirger teeth are more 

 pointed. 



The smaller chela measures four-fifths of the other, but fully 

 agrees with it in shape and characters. 



The ambulatory legs are of moderate length, those of the last 

 pair being little longer than the cephalothorax is broad. The 

 meropodites of the last pair are exactly three times as long as 

 broad, also those of the penultimate pair, which are 20 mm. long 

 and 6| mm. broad. Along their anterior edge the meropodites 

 are covered with depressed acute granules, and they appear a little 

 granular on their outer surface, especially near the anterior 

 margin, except those of the last pair, which are quite smooth. The 

 following two joints are likewise beset, on their fore edge, with 

 small acute teeth or granules, and a few occur on the posterior 

 margin ot the propodites. The slender and slightly arcuate 

 dactylopodites taper regularly to\\ ards their pointed tips, and are 

 longitudinally ridged both on their outer and inner surfaces. 

 Those of the second and third pairs are furnished, at the base of 

 their posterior margin, only with one spinuliform tooth, those 

 of the fourth and fifth pairs with two or three ; several spinuli- 

 form teeth are observed along the anterior edge oi these joints. 



In colour the cephalothorax is of an olive-green, that is hghter 

 on the gastric region and on the sternum than elsewhere. The 

 postfrontal crest, the margins of the orbits and of the front, the 

 granules of the antero-iateral margin, and the tooth of the epistome 

 are yellow. The chelipedes are greenish yellow, the ambulatory 

 legs reddish yellow. 



Potamon {Potamoncaites) auhryi H. M.-E. is a different species. 



