4 FOSSIL MALACOSTRACOUS CRUSTACEA. 



breadth of the front, and the more even transverse direction of the nuchal furrow, indicate 

 a difference between the two forms which I consider sufficient to warrant a distinct generic 

 place. 



The resemblance is still so striking in the general form of the carapace, the existence 

 of four triangular teeth on the latero-anterior margin, and the waved outline of the front, 

 that I have thought it desirable to express the similarity in the name applied to it. The 

 genus Xantho itself, as it was left by Prof. Milne Edwards, requires a complete revision, 

 and ought probably to be considered as comprising three or four genera, an arrange- 

 ment which that distinguished naturalist suggests by the sections which he has himself 

 indicated. 



Xanthosia granulosa, sp., M'Coy. Plate 1, fig. 13. 



Margine latero-anteriore lobis quatuor obtusis. 

 Reussia granulosa, M'Coy. 



With some hesitation I have referred the species indicated, but neither figured nor 

 described, by Prof. M'Coy, under the name of Reussia granulosa, to the present genus, 

 instead of that to which the author had assigned it. The specimens which I have had an 

 opportunity of observing are scarcely sufficient to supply me with any satisfactory 

 characters, but such as exist lead me to consider the species as more nearly allied to 

 Xanthosia than to Reussia of M'Coy. The general form of the carapace is very similar 

 to that of the foregoing species, but the latero-anterior margin, instead of having four 

 rather acute teeth, has that number of obsolete lobes; this margin also extends somewhat 

 further back than in the former. The regions are very well marked, and are even more 

 gibbous than in X. gihbosa. The carapace is evenly covered with minute and regular 

 granulations. 



Length of the carapace, 7 inch; breadth, 1\2 inch. 



It has hitherto been found only in the upper Greensand of Cambridge, where it is 

 very rare. The specimen figured, and from which the above imperfect description is 

 taken, is in Mr. Carter's collection. 



Genus — Etyus, Mantel/. 



Char. Gen. Testa transverslm elliptica, bis fere latior quam longior, tuberculata, 

 sulco nuchali transverso fere recto in medio divisa. Orbita oblonga?, approximata?, supra 

 tuberculis tribus subtus excavatis armatse. Pedes longi, gracilis. 



