34 MR. J. CAETEE ON THE PALEONTOLOGY OF [Feb. 1 89 8, 



the lengtli of the sternal plastron, a fifth wider than long, slightly 

 pointed and retroflexed, Male abdomen wide at the base, tapering 

 rapidly to a small triangular telson ; third, fourth, and fifth seg- 

 ments coalescent. Third joint of the endopodite of the external 

 maxilliped thrice as long as wide ; exopodite half the width of the 

 endopodite. Limbs undetermined. Width of carapace = 2 inches. 



HemarJcs. — The specimens which have afforded the foregoing 

 scanty detail of character are of interest because they constitute, so 

 far as I know, the only evidence obtained as to the occurrence of 

 any representative of the genus Neptunus in British rocks. A 

 considerable number of species — some twelve or fifteen — occur in 

 foreign Tertiary beds and have been described by Milne-Edwards 

 and by Stoliczka. 



Affinities. — All the species are characterized by having a series 

 of eight or ten pointed processes upon the antero-lateral margin, the 

 last of which is prolonged into a long spine. The British examples, 

 although not well-preserved, are clearly referable to the genus 

 Neptunus. The characters of N. vectensis, so far as known, closely 

 resemble those of A\ Larteti, Milne-Edw. 



Distribution. — Hamstead Beds (Cor6wk-bed), Hamstead, Isle of 

 "Wight. Two specimens are in the Woodwardian Museum. 



Genus Poetufites, Bell. 



POETTJNITES INCEETA, Bell. 



1858. Bell, Monogr. pt. i, p. 21 & pi. iii, figs. 1-5. 



Supplementary. — The dorsal surface of the carapace is smooth or 

 minutely granulated. Areolar tubercles almost obsolete. I have 

 not met with specimens showing the retroflexion of the last pair of 

 legs or the form of their terminal joint. Average width of adult 

 carapace = 20 to 40 mm. ; average length=16 to 26 mm. 



In stating the dimensions Bell accidentally reversed the relative 

 proportion of length to width. 



Affinities. — The wide orbito -frontal border, the three equally 

 prominent meso- and protogastric lobes, and the narrow, arcuate, 

 transverse epibranchial lobe readily distinguish this species. It is 

 well described by Milne-Edwards, who refers to the zoological 

 alliance of the genus, and agrees with Bell in classifying it with 

 the Portunidae. Eeuss described a species from the London Clay 

 which he named Leiochilus Morrisi; subsequently he considered 

 Portunites incerta. Bell, to be identical with this species, but his 

 description and figure apply so much more closely to the form 

 which he described in the same paper as Pseuderiphia M'-Coyi 

 (=Xanthilites BoiverhanJcii^^elV) than to Portunites incerta as to 

 suggest the probability that Leiochilus Morrisi may be a variety of 

 the former of these species. 



Distribution. — London Clay. I have two specimens in my col- 

 lection ; another from the Bed Crag (derivative) is in the Wood- 

 wardian Museum. 



