Fresh-water Entornostraca of South America. 27 



Fam. Macrothricidae. 



Gen. Crriinaldina, Richard. 



Generic Characters. — Carapace rather compressed 

 and of broadly quadrangular shape, being transverly truncated 

 behind. Valves well developed, permitting the whole of the 

 tail to be obtected, lower edges fringed with rigid setæ. 

 Head not defined above from the carapace by any depres- 

 sion, procumbent, and terminating in a short deflexed ros- 

 trum carrying the antennulæ, fornix very distinct, extending 

 as far as the tip of the rostrum. Eye normally developed; 

 ocellus very small. Antennulæ slender, scarcely curved, with 

 transverse rows of minute spikes anteriorly. Antennæ unusually 

 feeble in structure, rami slender, and narrow, with the usual 

 number of natatory setæ, none of which is conspicuously 

 transformed. Labrum forming a conical expansion below. 

 Five pairs of legs present, the 3 anterior ones without any 

 trace of epipodites, the last 2 with these appendages of 

 quite an unusual large size and sacciform; exopodite of last 

 pair well developed, lamellar, and provided with a very large 

 recurved seta clothed on both edges with exceedingly long 

 and delicate cilia. Caudal part of very large size, lamel- 

 larly expanded and very mobile, anal denticles disposed in 

 several separate sets, caudal claws of moderate size, caudal 

 setæ much elongated, and distinctly biarticulate. Intestine 

 not forming any coil, but provided in front with 2 small 

 cæcal expansions. Male very like young female speci- 

 mens, the secondary sexual characters being only faintly 

 indicated. 



Remarks. — This genus, established by Mr. Richard 

 in the year 1892, is a very distinct one, differing, as it does, 



