REPORT ON THE OSTRACODA. 39 



than one-third of the length ; end view broadly ovate, widest toward the ventral margin ; 

 surface of the shell smooth. Length, l-43d of an inch (•57 mm.). 



Dredged in Simon's Bay, South Africa, 15 to 20 fathoms (Station 140); Port 

 Jackson, Australia, 2 to 10 fathoms. The anterior depression of this species suggests 

 doubt as to the propriety of its genuine location as a Pontocyjyris, but I do not know 

 of any genus, except perhaps Bythocypris, to which it could with propriety be referred, 

 its anatomical characters being quite unknown. 



[PI. XV. fig. 6, a-d. a Carapace seen from left side, h from above, c from below, 

 d from front. All magnified 60 diameters.] 



Argillcecia, G. 0. Sars. 



Air/ilheda, Sars, Oversigt af Norges marine Ostracoder, 1865. 



Argillcecia, Brady, Crosskey, and Robertson, Post-Tertiary Entomostraca, 1874. 



Valves equal, smooth, elongated, moderately robust, scarcely higher in front than 

 behind, more or less angulated at the junction of the posterior and ventral margins. 

 Anterior antenna (PL IV. fig. 5) robust, five-jointed, first joint large and stout, the rest 

 beset on the lower margins with strong spines, and on the u^sper margins, especially in 

 the male, with numerous long setae ; posterior antennae (PL IV. fig. 6) short and thick, 

 otherwise as in Pontocypris ; the setae of the antepenultimate joint in the female short, 

 in the male very long, and reaching much beyond the terminal claws. Mandibles 

 (fig. 7) almost as in Pontocypris, the palp, however, having only three or four setae 

 (" one," Sars) in place of a branchial plate. Palp of the second pair of jaws indistinctly 

 three-jointed (fig. 9) bearing several terminal setae (" ending in a single claw," Sars). 

 First pair of feet (fig. 10) strong, ending in two nearly equal claws; second pair unlike 

 the first, and almost like those of Pontocypiis ; last joint very short, and bearing three 

 setae, of which one is very long and curved. Postabdominal rami short, attenuated 

 towards the apices, terminal claws very small. Eye wanting. 



The anatomical details of Argillcecia ehurnea, as shown in PL IV., do not in all 

 respects coincide with Sars' generic description ; the antennal setae of Argillcecia ehurnea 

 are much longer and more slender than ought to be the case, the branchial setae of the 

 mandible-palp are more numerous, and the second pair of maxillae seem to be some- 

 what difierent in structure ; yet, notwithstanding these divergences, I prefer, for the 

 present at least, to place this species in the already established genus, rather than to 

 create a new one on what might perhaps prove to be insufficient grounds. The genus, 

 though widely distributed, does not seem to contain a large number of species, and 

 these, like most of the Cypridce, present so few peculiarities of external form that their 

 identification is a difficult matter in the case of fossil species and of recent empty shells. 

 The subacute infero-posteal angle, and the overlap of the right valve in the centre of the 

 ventral surface, are the only tangible distinctive marks, so far as the sheU is concerned. 



