40 ME. J. CAETEE ON THE PALEONTOLOGY OF [Feb. 1 898, 



the several British forms, which he regarded as varieties of one 

 species, of which X. Leachi is the type. I fully concur with these 

 experienced carcinologists in this opinion. It may, however, be 

 permissible and convenient provisionally to regard these varieties 

 as specifically distinct, and to continue the names employed by 

 Bell, with the object of determining by future observation any 

 special valae or interest, either biological, phylogenetic, or geological, 

 which may attach to them. 



Xanthopsis BisPiNOSA, M'Coy. 



1858. Bell, Monogr. pt. i, p. 15 «& pi. i, figs. 5 & 6. 



Supplementary. — I apprehend that the dentition of the inner 

 border of the dactylopodite represented by Bell (fig. 5) is- in- 

 accurate. 



Xanthopsis Leachii (Desmarest). 



1858. BeU, Monogr. pt. i, p. 14 & pi. i, figs. 1-4. 



Supplementary. — The punctation of the dorsum of the carapace 

 varies according to the stage of growth. In small specimens the 

 puncta are so close as to produce a reticulated appearance ; they 

 become more widely separated as growth advances, and in large 

 specimens they are more than a diameter apart. The large tubercle 

 upon the dorsum of the hand, near the carpal articulation, and 

 those upon the marginal crest are more or less obsolete in many 

 specimens. 



Bell figured a nodulated form which he considered to be that 

 of a variety of X. Leachi. I have met with a number of similar 

 examples, most of them from Alum Bay, Isle of Wight ; but it is 

 not peculiar to that locality, as specimens from the London Clay of 

 Sydenham and Bognor are in the British Museum. This form 

 nearly resembles a variety of X. Dufourii, Milne-Ed w., but Milne- 

 Edwards regards it as a nodulated variety of X. kispidiformis, 

 Schloth., the occurrence of which at Sheppey is quoted by M'Coy. 

 X. Jiispidiformis and its varieties are fully described and profusely 

 figured by Eeuss and by Milne -Edwards. I am, however, unable 

 positively to determine the precise form to which Schlotheim 

 originally applied this name. 



Distribution. — London Clay. 



Genus Plagiolophtjs, BeU. 

 Plagiolophtjs "Wetheeellti, Bell. (PI. II, fig. 6.) 



1858. Bell, Monogr. pt. i, p. 19 & pi. ii, figs. 7-13. 



1859. Grly^hithyreus affinis, Eeuss, 'Zur Kenntniss foss. Krabben,' Denkschr. 

 t. Akad. Wisseusch. Wien, vol. xvii, p. 53 & pi. x, figs. 4 & 5. 



1861-65. Plagioloplius Wetherelli, Milne-Edwards, ' Hist, des Crust. Podophth. 

 Foss.' Ann. Sci. Nat. ser. 4, vol. xiv, p. 358, pi. xxxii, fig. 2 & pi. xxxiv, fig. 1. [?] 



Supplementary. — Carapace approximately quadrate in outline, as 

 long as wide in the early stage of growth, becoming a fourth or 

 fifth wider as growth advances. Orbito-f rental border as wide as 

 the carapace is long. Mesogastric lobe small, confluent posteriorly 

 with a small ancrular urogastric lobe of unusual form — which is 



