CORYSTOIDEA. 301 



angle, which is excavate. Inner antennae very oblique; outer short 

 and nearly naked. 



The genus Kraussia is instituted for a species figured by Krauss, in 

 his work on South African Crustacea, as a Platyonychus* (De Haan, 

 Portumnus of Leach) ; and for another described and figured by De 

 Haan as a Xantho.f It is very far removed from Xantho, and not 

 remote in its relations from Portumnus. Yet it appears to be more 

 closely like the Corystoidea, especially Thia, and we therefore arrange 

 it in this group. It differs widely, in fact, from Portumnus and the 

 related genus Platyonychus, in having the postero-lateral margin much 

 shorter than the antero-lateral, in being a little wider than long, in 

 having the front two-lobed and denticulate, and in the outer antennae 

 not being as naked, although less hairy and shorter than in most other 

 Corystoid species, a peculiarity in which it is near Trichocera. More- 

 over, the surface in one of the species, if not both, is marked trans- 

 versely by interrupted, obsolescent lines, having a crenulate margin, 

 as in the Hippidea, and some other Anomoura. 



The abdomen in both sexes is short and narrow; in the male five- 

 jointed, in females seven-jointed. The tarsi of all the eight posterior 

 legs are thin ensiform. The buccal area is somewhat oblong, a little 

 narrower behind. Orbit with two indentations in the margin above. 

 Internal orbital fissure filled or nearly so, by the first joint of the 

 outer antennas. Eyes of moderate size. In our specimen, the tarsus of 

 the second, third, and fourth pairs of legs is a thin blade, concave in 

 outline above, with the back thin except a small broad triangle at 

 base, which is concave in its surface, and the penult joint is flattened 

 above with the anterior of the upper margins subcristate. The tarsus 

 of the fifth pair is a similar blade, but with a broad concave back 

 reaching to its tip. The inner antennae make an angle of about sixty 

 degrees with one another, and are but imperfectly retracted into fos- 

 settes, the fossettes being very shallow. 



The Trickocera porcellana of A. White (Voy. Samarang, Crust., p. 

 69), appears to be a Kraussia; and is possibly identical with Krauss's 

 species. 



* Platyonychus rugulosus, KRAUSS, page 26, Plate 1, fig. 5. 

 j- Xantho integer, DE HAAN, Faun. Japon., p. 66, PI. 18, fig. 6. 



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