from the Chinese Seas. 357 



becomes gradually and sli^ditly more and more emarginate 

 towards tlie hinder end of the body, but is never strongly so, 

 for it is only in about the last four keel-bearing segments 

 that the posterior angle of the keel is [)roduced into a point 

 Avhich surpasses the posterior border of the tergite ; the lateral 

 border of the keels very lightly convex and very finely denti- 

 culate, the anterior angle rectangularly or posteriorly obtusely 

 rounded; the anterior border very lightly sinuate, being 

 lightly convex in its basal half and nearly straight in its distal 

 half, the upper surface of the keel sculptured. The caudal 

 process with a spiuiform tubercle in the middle of its length, 

 the tip truncate. Anal sternite not distinctly tubercular. 



Legs stoutish ; femur a little longer than the trochanter, 

 but distinctly shorter than the tarsus ; tibia much shorter 

 than trochanter, almost twice as long as patella, but barely 

 (except on the last somite) half the length of the tarsus. 



Total length 17 millim. ; width across keels 3*3, between 

 them 1-8. 



Loc. Da-zeh Valley, 60 miles inland of Sam-Moom Bay, 

 Che Kiang, China [Bassett- Smith). 



Polt/desmus paludicola, sp. n. (PI. XI. fig. 5.) 



Very nearly allied to the preceding species in all its cha- 

 racters, but with the sculpturing stronger and the keels much 

 narrower, being in fact in the rriiddle of the body scarcely 

 Avider than long, with the anterior border not sinuate but 

 straight. The colour, too, is more of a miiform slate-grey, 

 there being less red about the keels and less fuscous on the 

 legs and back. 



Length 15 millim. ; width across keels 2*6, between 

 keels 1'6. 



Loc. Wo Lee Lake, 25 miles S. of Ningpo {Bassett- Smith). 



[PolT/desmus compactus, sp. n. (PI. XL fig. 6.) 



Colour a slate-grey, slightly tinged with red ; margin of 

 the keels reddish ; legs reddish yellow. 



{Antenna; fractured.) 



The keel-bearing parts of the segments in contact, the keels 

 overlapping each other. The dorsal surface polished ; the 

 first tergite large, not sculjitured, its anterior border evenly 

 convex, its posterior border very lightly emarginate mesially, 

 and at the sides directed obli(juely forwards, its angle acute. 

 The rest of the segments nearly flat above, lightly convex; 

 the sculpturing into polygonal areas is weak and does not 



