NECROSGARCINUS. 21 



rather less raised from the general surface, but the tubercles are somewhat more prominent, 

 and in the young state acute at the apex. The rostrum is acutely triangular, longer than 

 broad, and armed on each side at its base with a very small tooth. The tubercles are more 

 numerous than in N. Bechei, being not fewer than twenty ; the five additional ones are 

 as follows : — the single one behind the rostrum, which in the former is obsolete, is here 

 conspicuous ; there is one on each side of the metagastric lobe in addition to the mesial one, 

 and one on each hepatic region. The tubercles are ^mostly arranged in right lines; thus 

 besides those on the median line, the seven anterior ones form a perfectly straight Hue 

 across the anterior part of the carapace, and there is an equally regular longitudinal series 

 on each side. The middle portion of the nuchal fun-ow does not extend so far backwards 

 as in the former species ; the edge of the posterior margin is less raised, and the hollow 

 immediately anterior to it not so deep. The orbits are round, as in A. Bechei, but the 

 fissures are less marked, and there is no tooth between them. 



Amongst the specimens in the British Museum and in Mr. Cunnington's collection 

 there are several fragments of limbs which I can scarcely doubt belong to this species. 

 Figs. 4 and 5 of Plate V represent the hand and arm probably belonging to the same 

 individual. These are covered with tubercles ; the hand is as broad as it is long, the 

 finger short and stout ; the arm about twice as long as it is broad. I am confirmed in 

 the opinion that these belong to Necrocarcinus by the figure of the hand of N. infiatm, 

 which I have received through the kindness of M. Adolphe Milne Edwards, which has 

 the same general aspect ; and they can only appertain to the pi'esent species. I conclude 

 also that figs. and 7 represent fragments of some of the ambulatory legs. 



Length and breadth of the carapace in the largest specimen observed, 2 inches, 



Ohs. All the specimens I have yet seen, with one exception, are from the Upper 

 Greensand of Warminster and Maiden Bradley, in Wiltshire, and they are somewhat 

 numerous in the British Museum and in the collection of Mr. Cunnington, of Devizes. 

 The exception to which I have alluded is a very large individual in the collection of Mr. 

 Norman, of Ventnor, from the Chalk Marl capping the firestone at St. Lawrence, in the 

 Isle of Wight. This is by far the largest I have seen, being two inches in diameter, 

 whereas the largest from the other localities is not quite an inch and a half. 



I have great pleasure in recording the obligations I am under to Mr. Henry and Mr. 

 Woodward, of the British Museum, for their constant kindness and attention, and the 

 great assistance they have afforded me in the preparation of this work, by dedicating to 

 them the present interesting species. 



Necrocarcinus tricarinatus, mild. Plate IV, figs. 9 — 11. 



Testa depressa tuberculata, carinus tribus, longitudinalibus, quarum una in medio 

 regionis cardiacse, et altera utrinque in regione branchiali. 



