14 FOSSIL MALACOSTRACOUS CRUSTACEA. 



form, two at least of the species of the genus ; the number and variety of the specimens 

 fully making up for their individual fragmentary condition. I may state that it was by 

 carefully clearing a beautiful specimen of Mr. Wetherell's and one in my own collection, 

 that I have been able to demonstrate the minute and rarely preserved parts about 

 the antennal, the orbital, and oral regions, of which I have given a diagram.* 



Xanthopsis Leachii, sp., Desmarest. Plate I, figs. 1 — 4. 



Testa valde convexa, tuberculis magnis, prominentibus, margine antico-laterali 

 tuberculis tribus obtusis ; fronte incurvo. 



Cancer Leachii, Desmarest. Crust, foss., p. 95, t. viii, figs. 5, 6. 

 Xanthopsis nodosa, M'Coy. Ann. Nat. Hist., 1849, p. 163. 



Descr. Carapace not more than from one sixth to one fifth wider than it is long ; 

 much elevated in the middle, so that its height, from a line drawn horizontally from the 

 posterior margin to the front, is not less than three sevenths of its length ; it slopes 

 gradually to the sides, more considerably to the posterior margin, and almost abruptly 

 to the front, which becomes nearly vertical ; frontal lobes rounded and thick ; latero- 

 anterior margin with three obtuse rounded tubercles, diminishing in size and prominence 

 forwards, the posterior one being on a line with the urogastric lobes ; tubercles of 

 the carapace large and rounded ; the metagastric tubercle often longitudinally divided by 

 a very shallow depression ; those of the branchial region prominent, the posterior one 

 extending forwards in a low, rounded ridge : the puncta on the surface considerably 

 smaller than in X. bispinosa, particularly towards the anterior portion, where they are 

 extremely small and shallow ; the interspaces between the puncta studded with extremely 

 minute granulations, which, in particular lights, are easily detected with a lens : chelae of 

 the male somewhat larger than those of the female, the right being ordinarily the larger ; 

 the superior margin forming a ridge which on the larger hand has ordinarily seven, 

 and on the smaller four tubercles : there are also three distinct elongated tubercles 

 not far from the junction with the wrist, one near the base of the immoveable finger, 

 and a slight elevation near the moveable one. The fingers each furnished with about two 

 strong tubercular teeth ; abdomen of the male hastate, as given in the description of the 

 genus ; that of the female, broad oval. 



05s. This may with great propriety be considered as the type of Xanthopsis, as all the 

 characters by which the genus is distinguished are developed in it, to the greatest degree. 



* Plate 1, fig. 7. 



