18 FOSSIL MALACOSTRACOUS CRUSTACEA. 



Length of carapace, 12 inch; breadth, 1 inch. 



Found hitherto only in the upper Greensand of Cambridge. 



Obs. A certain general resemblance to some of the species of Palaocorystes led 

 Professor M'Coy to consider this species as belonging to that genus, which is identical 

 with his Notopocorystes. Hitherto there has been no attempt to separate it from that 

 genus. The several forms of the carapace certainly bear a not very remote resemblance 

 to P. Broderipii ; but, as it appears to me, the relation is only superficial and on closer 

 examination the form and character of the carapace itself are essentially different, whilst 

 in the far more important points, the structure and form of the orbit and of the frontal 

 region, the diversity is so great as not to admit of any doubt as to their generic distinction. 

 The following are the discrepancies to which I have referred. The carapace in the 

 present species is much more square, the anterior and posterior portions being considerably 

 less narrowed than in any of the species of Palaocorystes ; the sculpture of the anterior 

 half of the carapace is totally unlike any other species, not only of Palaocorystes, but of 

 every other Crustacean form with which I am acquainted, with the exception of Eumorpho- 

 corystes sculptus of Count von Binkhorst, to which I shall again refer. But when we 

 examine the orbital and frontal regions, which are of so much more importance as generic 

 characters, the discrepancy is still more striking. The breadth of the front between the 

 orbits, equalling the long diameter of each orbit, and especially the enormous size of these 

 cavities, extending to the antero-external angle of the carapace, at once remove the species 

 from a genus in which the front is of moderate size, and the comparatively small and 

 round orbits do not even approach the external angle. 



It is certainly remarkable that the peculiar sculpture of the carapace should also occur 

 in a Continental species, to which I have just referred, and to which the excellent palaeon- 

 tologist above named has assigned a distinct generic position. The form and general 

 character of Eumorphocorystes are, however, not only essentially distinct from the species 

 now under consideration, but approximate it still more to Palceocorydes, although I consider 

 Count von Binkhorst quite justified in the separation he has made. 



Professor M'Coy alludes to the comparative rarity of this species. I believe it has 

 hitherto been found only in the upper Greensand of Cambridge, and it was, with great 

 propriety, dedicated to the gentleman in whose fine collection of the fossils of that locality 

 the specimen occurred from which the first description was taken. 



