84 Recordf! of the hid inn illuseuvi. [Yol. XIV, 



The antero-Iateral border {text-fio;. ]a) is sharper and much more 

 stron«iy reflected iijiwards than in P. andersonianum. It is separated 

 from the coarsely granular epibranchial region by a deep smooth groove 

 aiul its margin, instead of being serrulate, is spinulose. At the posterior 

 end of the border the spinules are small and closely packed ; anteriorly 

 they are larger and more Avidely spaced ; the foremost is a large epi- 

 branchial tooth which frec|uently bears one or more granules on its 

 edges. 



The antennular fossae and epistome are much as in the related 

 form. The ischium of the outer maxillipedes (text-fig. 16) bears the 

 usual groove ; the merus is as long as broad and is rounded in outline, 

 rather than irregularly hexagonal as in typical specimens of P. ander- 

 sonianum. 



The chelae are more or less of a size. The merus is similar to that of 

 P. andersonianum,, but the granulation is much crisper, the serrated 

 margin being spinulose and the tooth near the distal end of the inner 

 face becoming a sharp spine with accessory spinules at the base. The 

 carpus is smoother above and is not, or not appreciably, umbilicate. 

 On the upper surface of the palm there are some small and inconspicuous 

 tubercles w^hich extend a little way down the outer face ; the lower half 

 of the outer surface is quite smooth. The fingers are more compressed 

 than in the alhed species and the teeth on their inner margins are much 

 larger. The dactylus is grooved in the usual way and bears some sharp 

 tubercles at the base of its upper surface. 



The walking legs are rather more slender than in P. andersonianum,, 

 but the anterior margin of the propodus, as in hat species, is double- 

 edged. The propodus of the penultimate leg is two and a half times, 

 and that of the last leg twice as long as broad. 



In the abdomen of the male (text-fig. Ic) the length of the sixth 

 segment is rather more than half its greatest breadth ; the seventh is a 

 little broader than long. 



The carapace in six specimens yields the following measurements 

 (in mm.). 



Tlie eggs borne by an ovigerous female are very large, about 3 mm. 

 in diameter. 



Potamon hrowneanum may be distinguished from P. andersonianum. 

 (i) by its more convex upper surface, (ii) by the incompletely circum- 

 scribed mesogastric areola, (iii) by the deeply bilobed front, (iv) by the 

 granulation, which, except on the chelae, is everywhere crisper — parti- 

 cularly on the antero-Iateral borders of the carapace, the lower borders 

 of the orbits and the merus of the chelipedes, (v) by the smooth outer 

 surface of the chelae and larger dactylar teeth and (vi) by the more 

 slender propodus of the walking legs. From P. fealianum. (Wood- 

 Mason), which it resembles in the convexity of the upper surface of the 

 carapace, P. broumeanum, is distinguished by the stronger curve and 

 sharper spinulation of the antero-Iateral borders, by the more deeply 

 bilobod front and the nuieh less conspicuous frontal eminences. 



