XANTHOPSIS. 15 



Such are particularly the convexity of the carapace, its tuberosities, the curvature of 

 the front, and the development of the processes of the latero-anterior margin. The general 

 minutely granulated surface of the interspaces between the puucta is peculiar to it, 

 as, in the others, it only exists in an almost imperceptible degree, and that only in the 

 neighbourhood of the marginal tubercles. The remarkable difference in the convexity of 

 the carapace wiH be found detailed in the account of the next species, X bispinosa. 



I have thought it proper to restore the name of '' LeacJdi" to this species, as I think 

 there can be httle doubt that this was the type to which Desmarest applied the term ; 

 and it is but fair, both to the giver and the object of the honour, not to change it 

 unnecessarily. It is, however, with great reluctance that I venture to alter anything 

 which has the sanction of Professor M'Coy's authority in this department of natural 

 history, to which he has given a stimulus, and on which he has afforded us so much 

 valuable information. 



Numerous specimens of this species exist in the British and Cambridge Museums, 

 in the collections of Mr. Bowerbank, Mr. Wetherell, Mr. Prestwich, in my own, and in 

 every collection of London Clay fossils, derived from various localities — from the northern 

 suburbs of London, from the Isle of Sheppey, and the opposite shore of Essex, and one, 

 somewhat different from the normal form, from Alum Bay in the Isle of Wight, and which 

 is figm'ed in Plate I, fig. 10. 



Xanthopsis bispinosa, M'Coy. Plate I, figs. 5, 6. 



Testa modice convexa, tuberculis depressis ; fronte fere horizontali ; margine antico- 

 laterali spmis duobus depressis, posteriore majore. 



Xanthopsis bispinosa, M'Coy. Ann. Nat. Hist., 1849, p. 164. 



Descr. Carapace nearly one third broader than long, transversely oval, moderately 

 convex, sloping gently to the sides, more decidedly to the posterior mai'gin than to 

 the front, which is moderately incUned ; the frontal lobes rather flattened ; latero-anterior 

 margin having only the posterior two tubercles, which are modified into depressed 

 subacute spines, of wliich the hinder one is the longer, and is slightly recurved ; the place 

 of the anterior tubercle marked by a sUght projection, which, however, varies in degree in 

 different individuals. I have one in my collection in which it is so conspicuous as to have 

 led me at first to consider it as specifically distinct. Tubercles of the carapace much less 

 prominent than in X. Leacldi, the puncta of the surface rather large, neaily as much so 

 on the anterior portion as on the rest, and not obsolete in the grooves between the 

 tubercles ; chelae as in X. Leacldi ; the tubercles of the crest of the hand being, however, 

 less prominent, and one or two of those towards the finger nearly obsolete ; abdomen 



