I9I3-] Stani^ey Kemp : Crustacea Decapoda. 293 



examples. The fore lobe of the mesogastric areola is well defined 

 and the median groove is continued, though not always very clearly, 

 almost to the margin of the front. 



The epigastric and post-orbital crests are sharp and distinct. 

 The epigastric crests are narrow and are separated from the post- 

 orbitals b}' well-defined grooves ; though considerably in advance of 

 the post-orbital crests in the middle line, they slope away on either 

 side and in conjunction with these crests form a common curve 

 across the anterior portion of the carapace. The post-orbital crest 

 is sharply cut and trenchant up to the point where the cervical 

 groove would cut it, if it were defined, but beyond this it is broken 

 up into a number of sharp tubercles (fig. i). 



The front in adults is much less than one-third the breadth of 

 the carapace ; in small individuals about one-third. Immediately 

 behind and parallel with its edge it bears a bilobed eminence which 

 in dorsal view almost or quite conceals the margin. In this respect 

 the species resembles Potamon pealianum, but the eminences are not 

 quite so pronounced. The edge is sometimes very feebly bilobed 

 when seen from in front. 



In the smaller specimens there is only a faint indication of a 

 gap between the upper and lower borders of the orbit ; this feature, 

 however, is very strongly developed in the adult male. The antero- 

 lateral borders are sharply pinched off from the carapace, strongly 

 crenulate and well arched, and the epibranchial tooth is well deve- 

 loped. 



In the abdomen of the adult male (fig. 3) the sixth segment is 

 twice as broad as long and the seventh a little more than three 

 quarters as long as broad. 



The mandibular palp is simple. The flagellum of the exopo- 

 dite of the external maxillipedes is vestigial in six specimens (fig. 2), 

 but moderately developed in the seventh (a small example). The 

 merus of the endopod is nearly as long as broad. 



The chelipedes are almost or quite equal in all the specimens ex- 

 amined. The external surfaces of the merus, carpus and propodus 

 are squami-rugose ; the spine at the inner angle of the carpus is 

 strong and sharp The fingers are as long as the palm, pitted in 

 the large example, both pitted and fluted in the smaller individuals. 

 The upper border of the propodus bears vesiculoas granules, some 

 of which are also found at the base of the dactylus. 



The dact^di of the walking legs are longer than their propodi : 

 in the two middle pairs the propodus is rather more than two and 

 a half times as long as broad. 



In an adult male, the type specimen, the carapace is 63 mm. 

 broad, 49 mm. long and 29 mm. deep. In the next largest speci- 

 men, also a male, the breadth of the carapace is 26 mm., its 

 length 20 mm. and its depth 11 '5 mm. 



The species which bear the closest resemblance to Potamon 

 decourcyi appear to be Potamon [Potamon) pealianum, Wood-Mason, 

 and Potamon {Potamiscus) annandalei, Alcock. From the former 

 it differs in the total suppression of the cervical groove, in the 



