34 FOSSIL MALACOSTRACOUS CRUSTACEA. 



Length of the whole animal, 7 to 8 inches ; length of carapace, 3 inches ; breadth 

 of carapace, 1^ inch. 



Obs. There can be no possible doubt of the relation of this very interesting fossil. 

 It possesses all the distinctive characters of the family Scyllarida?, as represented by 

 the three recent genera Scyllarus, Thenus, and Ibacus. In especial, it resembles them 

 in that peculiarity in the structure of the external antennas, which constitutes one of the 

 most interesting examples of morphology in the whole class. These organs, instead of 

 being developed, as in all the other groups of the order, into long, slender, multi-articulate 

 filaments, to which the basal joints serve only as strong supports and means of attachment, 

 are in the present family deprived of the terminal filament altogether, and the basal joints 

 are developed into very broad, flat implements, which doubtless serve the purpose 

 of shovels, to enable the animal to scuttle under the sand or mud in which they probably 

 pass the greater portion of their time. Although in all the numerous specimens of the 

 present species which I have seen, these organs are incomplete, there are sufficient 

 fragments to enable me to confirm the decided impression of its true relations which I first 

 received from the examination of other portions of the animal. 



Of the three recent genera of Scyllaridaa the present fossil most resembles the genus 

 Scyllarus in its general proportions, and particularly in the nearly parallel sides of 

 the abdomen ; but approaches more nearly to Thenus in the very strong, conical, prominent, 

 and slightly divaricating teeth of the rostrum. It differs strikingly from all the recent 

 forms in the distinctness, depth, and situation of the cervical sulcus of the carapace, which 

 is comparatively indistinct in all the recent species, but in this constitutes a very marked 

 character, and is so deep as to occasion the carapace to be often found broken across 

 at that part. The joints of the external antennae resemble those of Scyllarus in their 

 extension forwards, in which respect they greatly exceed those of both Ibacus and Thenus. 

 I have not been able to discover the eyes, nor the place for them, in any of the specimens 

 I have seen, and as the anterior margin has been very completely examined, I presume 

 that they are placed at the extreme external angle, as in Thenus, and not just within 

 the angle, as in Scyllarus, and still less probably midway between it and the rostrum, 

 as in Ibacus. In either of the latter cases they could not have escaped observation. 



The specimens, both from the Isle of Sheppey, and the northern suburbs of London, 

 and especially from the latter locality, are very numerous in the British Museum, and in 

 the collections of Mr. Bowerbank and Mr. Wetherell ; there are also two fragments in the 

 Hunterian collection in the museum of the Royal College of Surgeons, and Monsieur le 

 Capitaine le Hon has lately shown me a specimen consisting of a few segments of an 

 abdomen, which I instantly recognised as belonging to this species. It Avas from the 

 " Sable " of the neighbourhood of Brussels. 



