ARCILEOCARABUS. 43 



Obs. This beautiful and curious species was first made known by Professor M'Coy, 

 in his paper on ' British Fossil Crustacea,' so often quoted. With regard to its supposed 

 affinities, he has the following observations. " In all the characters of generic importance 

 which I have seen in these fossils, they approach the recent Palinuri or spiny lobsters ;" 

 and he applies to it a generic name in consonance with this supposed relation. What are 

 the characters in which the author has discovered this relation he does not inform us ; 

 but I have failed to find any such relation in the characters which have offered themselves 

 in the numerous specimens which I have had an opportunity of examining. In the general 

 rounded form of the abdomen it resembles the Palinuridae, in common with the Astacidae 

 and many other families, particularly the Crangonidae, with which I shall presently show 

 its relation ; but in the most important points in which the recent Palinuri agree amongst 

 themselves, and differ from other genera, the present fossil species does not exhibit 

 any such affinity. The front of the carapace does not possess any indication of the 

 peculiar structure of that part in the recent genus, and this is especially obvious in 

 the total absence of the two strong, projecting, supra-rostral spines, which exist in every 

 known species of that family. To set aside, however, all minor considerations, the form of 

 the anterior feet, a character so important in all this class, presents the most striking 

 discrepancy between the two forms ; instead of the simple termination of these limbs in a 

 single acute joint, not differing from the terminal portion of the other feet, which is seen in 

 all the recent species, the fossil animal has the remarkable development of this part 

 which characterises the genus Cranr/on, but in a still more marked degree ; the anterior 

 margin of the hand being truncated abruptly, and forming an opposing line to the 

 moveable finger, which in prehension would be applied to it in its whole length. I have on 

 this account considered it as probably belonging to the family Crangonidae, to which, it 

 appears to me, this important character, in the absence of any striking discrepancy in other 

 organs, indicates an obvious affinity. The name Archaocarabus, applied to it by Professor 

 M'Coy, was therefore, as I conceive, founded upon a misapprehension of its true relations ; 

 but I have not presumed to change it, a step which is only allowable under extreme 

 circumstances. 



This must be considered as pre-eminently a Sheppey fossil ; for, although occasionally 

 found in the northern suburbs of London, the great majority of the specimens which have 

 come under my observation, have been found in the former locality. They exist in the 

 British Museum, in the Woodwardian Museum at Cambridge, in the Hunterian Museum, 

 and in Mr. Bowerbank's collection, but from the very fragile texture of the crust, they are 

 all much broken. 



