FROM THE INLAND SEA OF JAPAN, 441 



Avas described last year by Dr. Caiman as Parath. sphiescens, both fingers of both 

 chelipeds are spoon-shaped : though in old males the fingers of the larger cheliped 

 become obtuse, gx*ada.illy losing their spoon-like shape, as may be observed in some 

 species of Leptodlus. Pot. spinescens becomes therefore the type of the new subgenus 

 Parapotamon. 



PotajVion (Parapotamon) spinescens, Caiman. 



Parathelphusa spinescens, Caiman, in Ann. & Mag. Nat. Hist. ser. 7 , vol. xvi. 1905, p. 156. 



Pour males and one female without eggs from the Yunnan-Fu Lake, China. 



In the youngest male and in the female of the same size the antero-lateral margins are 

 armed on each side with five spiniform teeth ; in the male, however, the last tooth on the 

 left side is rudimentary and a smaller granule is situated just before it. In the male the 

 right cheliped is somewhat larger than the left. The right chela, which is 24 mm. long, 

 is almost just as long as the length of the cephalothorax in the middle line; the fingers 

 are a little shorter than the palm and barely longer than the palm is high. Though the 

 dactylus is nearly straigbt, there is, however, a small hiatus between both fingers ; both 

 fingers carry fine punctuations, which are partly arranged in longitudinal rows. In 

 Caiman's somewhat larger male the dactylus was " slightly arched and very obscurely 

 furrowed." The oviter surface of the palm is quite smooth, finely punctate. The fingers 

 of the left chela are just as long as the palm. The anterior border, articulating with the 

 chela of the u[)per surface of the carpus, carries a few small denticulations ; otherwise 

 the upper surface is smooth, punctate. In the female the right chela is very slightly 

 larger than the left; the fingers are a little shorter than the palm and a little longer 

 than the latter is high. Pingers and palm of the left cheliped are equally long. The 

 fingers of both chelipeds are, in tliis male and in the female, spoon-shaped ; the margins 

 of the spoon-shaped tips of the fingers are white. The three other males are of much 

 larger size ; in the largest the cephalothorax is 54 mm. broad, the antero-lateral margin 

 of the right side is armed with five teeth, that of the left witii seven, the last being rudi- 

 mentary ; the first and second are grown together at the base, as are also the third and 

 fourth, (See Kote C on page 454.) 



Measurements in millimetres. 



1. 2. 3, 



6- 6. $. 



Greatest breadth of the cephalothorax at the level of the 



penultimate antero-lateral teeth St' 345 34 



Length of tlie ceplialotiiorax in the middle line, without the 



abdomen 38 25 24 



Distance between the external orbital angles 32 21 5 21 



Ereadth of the frontal border 14-5 10 10 



Length of the larger (right) chela 54 24 20 



Nos. 1 and 2 the largest and the youngest males, No. 3 the female. 

 Both specimens were collected, together with the types desciibed by Dr. Caiman, in 

 the lake at Yunnan-Pu. 



