The Fresh-water Entomostraca of Cape Province. 327 



Occurrence. This form also developed in great abundance in some 

 of my aquaria prepared with mud from the neighbourhood of Berg- 

 vliet. It was also found occasionally in some of the alcoholic samples 

 sent to me from the South African Museum. 



Distribution. Australia, South America. 



GEN. 8. ILYOCBYPTUS, G. O. Sars. 



Remarks. This peculiar genus differs considerably from the other 

 genera comprised within the family Macrothricidae, both in general 

 appearance and in structural details, and should perhaps more properly 

 be regarded as the type of a separate family. We know of three well- 

 defined European species, and to these have been added recently a 

 limited number of exotic forms more or less closely related to them. 

 To the fauna of Cape Colony belongs one species, to be described 

 below. 



25. ILYOCRYPTUS SORDIDUS (Lieviu). 

 (Plate XXXVII, figs. 1, 1 a-c.) 



Acanthocercus sordidus, Lievin. Die Brauchiopoden der Danziger 

 Gegeud. N. Schrifteu d. naturh. gesellsch. in Danzig, vol. iv, 2, 1848, 

 p. 34, pi. viii, figs. 7-12, 



Specific Characters Female. Carapace, seen laterally, subtrigoual 

 in outline, gradually expanding behind, with the posterior and inferior 

 edges of the valves of about equal length and passing into each other 

 by a very strong curvature, being throughout fringed with ciliated 

 setae, dorsal margin only very slightly arched and joining the free 

 edges of the valves at an obtuse angle ; superposed valves varying in 

 number according to age. Head comparatively small, seen laterally, 

 triangular in form, and defined above from the carapace by a distinct 

 depression, fornix rather prominent and terminating in front in an 

 angular corner ; inferior edge of head straight and horizontal, without 

 any distinct rostral projection. Eye remote from the front, with only 

 three or four refracting bodies ; ocellus a little smaller than the eye 

 and occurring at a short distance behind it. Anteunulae distinctly 

 biarticulate, proximal joint very small, distal joint long and slender, 

 linear in form. Antennae short and thick, not adapted for swimming. 

 Tail-piece large and compressed, conic-ally produced at the tip, and 

 exhibiting in the middle of the posterior edge a distinct sinus, supra- 

 anal margin occupying about half the length of the piece and armed 

 with about ten equal-sized denticles, anal denticles about fourteen pairs, 

 sub-marginal spines rather slender and somewhat curved, about nine on 



