The Fr?sh-titt'r Entomostraca <>J Cnjic Prortttcr. 339 



nuiTOwed and transversely truncated, with both the upper and lower 

 corners distinctly angular. Head only slightly procumbent, and 

 terminating in a rather prominent rostrum, slightly curved at the end. 

 Surface of valves sculptured with well-marked, somewhat curved 

 longitudinal striae, which at regular intervals anastomose with each 

 other, so as to form a rather conspicuous reticulation, and in the 

 anterior part are crossed by a number of transverse arcuate ridges . 

 posterior edges of valves exhibiting, just above the lower corner, two 

 or three slight creuulations. Ocellus smaller than the eye, and located 

 much nearer to it than to the tip of the rostrum. Antennulae not 

 nearly extending as far as the latter. Tail-piece rather narrow and 

 slightly tapered distally, with the infra-anal edge nearly straight 

 and terminating in an angular corner ; supra-anal angle rather promi- 

 nent, and occurring far above the middle of the piece ; marginal 

 denticles rather small ; sub-marginal combs inconspicuous ; apical 

 claws comparatively small, each with two unequal denticles at the base. 



Length of shell about O37 mm. 



Remarks. The above-characterised form is unquestionably identical 

 with Fischer's species, and is distinguished from the nearly-allied 

 Australian species A. clathratula, Gr. O. Sars, by a somewhat shorter 

 and stouter form of the shell, and more particularly by the presence of 

 distinct crenulatious of the hind edges of the valves at the iufero- 

 posteal corners, these crenulations being wholly absent in the former 

 species. 



Occurrence. Two or three specimens of this form were found in an 

 alcoholic sample taken by Dr. Purcell from a pond in the Cape Flats, 

 and kindly sent to me for examination. 



Distribution. Throughout Europe, Siberia, Iceland, Greenland, 

 North America. 



GEN. 12. CHYDOKUS, Baird. 



Remarks. The species of this genus may be easily recognised 

 by the more or less globular shape of the shell. Most of them are so 

 closely allied that their distinction is attended with no little difficulty ; 

 but there are also among them some more deviating forms, one of 

 which will be described below. 



39. CHYDORUS BARROISI (Richard). 

 (Plate XL, tigs. 6, 6 a, fe.) 



Pleuroxvs barmixi, Richard. Cladoceres recueillis en Syrie et en 

 Egypte. Revue Biol. du Nord de France, Tome vi, 1893, p. 16. 



