]02 DB- J. G. DE MAN ON A NEW PRE9HWATEE [Peb. 19, 



it extends laterally to the autero-lateral margin. The lateral 

 margins of the front, which is strongly deflexed, are very oblique 

 in both males and curve regularly into the anterior margin, which 

 is slightly emarginate in the middle ; the upper surface of the 

 front is finely granular and appears a httle concave in the middle. 

 The anterior"^half of the gastric region is distinctly granulate, and 

 the lateral parts of the upper surface show the usual finely- 

 granulate, transverse rugae. The rest of the upper surface is 

 smooth and punctate. The suborbital area is finely granulate and 

 separated from the branchial floor, which is covered with short, 

 tjausverse, granulate rugae, by a rather shallow groove ; this 

 groove, however, is bordered by a finely-granulate line. The 

 pleural suture limiting off the subhepatic and subbranchial regions 

 from the branchiostegite is defined anteriorly by two granulate 

 lines, just as in P. svprasulcahim Hilgd. 



The outer foot-jaws are furnished with a distinct furrow on the 

 ischium-joint in Hilgendorf's species ; but in the true P. hihjen- 

 doi'fi Pfeffer the "ischial line" is completely ivanting, at least in 

 the two males lying befoi'e me. 



The carpus of the anterior legs is covered above with very fine 

 granulate rugae, and is armed at the inner angle with & conical tooth, 

 beneath which a much smaller one ia seen. The immobile finger 

 of the chelipedes shows a deep longitudinal groove a little below 

 the middle of its outer surface, and above this groove still another 

 one that is less deep ; the outer surface of the dactylus is also 

 marked with two longitudinal grooves, the lower of wliich is, 

 however, rather shallow. Pfeffer describes these furrows as 

 " eiuen breitern und einen schmaleru Langseindruck." In the 

 species that was described by Hilgendorf there are no furroivs on 

 the fingers, at least none on the immobile. One observes on the 

 outer surface of the palm very short, vertical, finely-granulate 

 lines that gradually pass into very fine granules towards and on 

 the fingers. 



Measurements of the two specimens of Potamon hilgendorfi 

 Pfefi'er in millimetres : — 



Greatest Avidth of the carapace 26 14 



Length of the carapace 19 lOi 



Distance between the extraorb. angles . . 18^ 10| 



Breadth of the anterior frontal margin . . 8 4| 

 Length of the front, in the median line 



of the cephalothorax 21 1 1 



Thickness of the carapace 9 5 



Breadth of the orbits 5 3 



Height of the orbits . 31 ] | 



Length of the meropodites of the pen- 

 ultimate pair _ . . J 2 71 



Breadth of these meropodites 4 2| 



Length of the meropodites of the fifth 



pair lOi 6 



Breadth of these meropodites 4i 2 



