532 A. Milne- Edwards — On Necrozius Bowerbankii, 



border being much curved down. The latero-anterior borders are 

 continuous, almost without interruption, with the latero-posterior, 

 which latter are swollen. The frontal border (rostrum) projects a 

 little, and is slightly depressed in the centre. The basal joint of 

 the internal antennse is large, and it is articulated obliquely beneath 

 the front (rostrum). The basal joint of the external antennae is 

 short, not reaching to the front as in the Pseudo%kis of Dana, and in 

 Sphero%ius of Stimpson ; the articulation is free and is not lodged in 

 the internal obital cavity. With 0%ius on the contrary, this basal 

 joint is fully attached to the front. 



I have unfortunately been tmable to examine the endostome, so 

 that I could not determine the characters shown by the absence or 

 presence of the tubercles (cretes) which, in Ozius, are confined to the 

 neighbourhood of the expiratory canal of the branchial chamber. 

 The labial border was also concealed by the matrix, as are certain 

 parts of the specimen between the hands, so that I have been 

 unable to see if the border was complete, or sloped off as in Ozius. 



The anterior feet are very strong, and unequal in size, the smallest 

 being only half the size of the largest, their proportions and appear- 

 ance enabling one at once to distinguish the crustaceans of this 

 section. 



The walking feet are cylindrical ; they are not tuberculated, and 

 in this latter respect they resemble those of Ozius, 8phero%ius, and 

 Pseudo%ius. The abdomen in the male, as in the three preceding 

 genera, is composed of seven segments, all of which are free. 



This genus, as we have already said, is very near to Spherozius. 

 The basal joint of the external antennse in 0%ius reaches the front ; 

 in Pseudozms, Spherozius, Necrozius, it is distant from it. Pseudozius 

 has a rather elongated carapace, while in Spherozius the carapace is 

 more globular. This last genus differs from Necrozius in having a 

 more swollen caraj)ace, and the front is continuous, without inter- 

 ruption, by an insensible curve with the superior orbital border ; in 

 Necrozius, on the contrary, the internal orbital angles are well marked. 



Necrozius Bowerhankii, Alph. Milne-Edwards. — This pretty species 

 is from the London Clay of the Isle of Sheppey, which has furnished 

 so many interesting crustaceans.^ It formed a part of the rich 

 collection of Dr. J. S. Bowerbank, who, with his accustomed 

 scientific liberality, obligingly placed it at my disposal." 



This crab appears to be extremely rare, for Professor Bell does 

 not notice it among the Crustacea of the London Clay, and I have 

 never seen but this single specimen, perfectly preserved it is true, 

 although I have examined the collections of the British Museum, the 

 Museum of Practical Geology, and many others almost as rich. 



Description of the Species. — The carapace is closely covered 

 on all the salient parts with minute rounded granulations. The 



1 [The specimen here referred to, and which is figured in our plate (Plate XXT. 

 figs. 2 and 3), was obtained some years since by Dr. J. S. Bowerbank, F.R.S., from 

 the London Clay, Holloway, when the Great Northern Eailway was in course of 

 construction. Two less perfect specimens have, however, since been obtained from 

 Sheppey.— H.W.] 



* [The type-specimen here figured is now in the British Museum. — H. W.] 



