Tol. 54.] THE DECAPOB CKUSTACEA OP ENGLAND. 37 



segment divided into a median and lateral portions by longitudinal 

 ^grooves. Chelae elongate ; propodite about a third of the width of 

 the carapace in length, oval in section. Fingers very slender, 

 nearly as long as the hand ; inner border with, irregular acicular 

 denticles. Width of carapace =7 to 26 mm. Length of average 

 adult =20 mm. 



Remarhs. — In Cambridge Greensand specimens the tubercles on 

 the dorsal surface of the carapace are much less acutely prominent 

 than in those from the Gault — a condition which. Bell attributes to 

 -attrition. The difference is certainly normal and not accidental ; 

 inor is it peculiar to this species ; a similar modification of surface- 

 ►character occurs in most of the forms which are common to the two 

 deposits. The delicate chelae are very seldom preserved in situ in 

 "Cambridge specimens, but they occasionally occur in those from the 

 Gault. The detached hand (Bell, pi. i, fig. 11) which Bell supposed 

 to be that of Etyus Martini belongs to Diaulax Carteriana. 

 M'Coy's figure is inaccurate as regards the course of the scapular 

 sulci, and also in representing the mesobranchial lobe as bearing 

 'two tubercles instead of one. 



Distribution. — Abundant in the Cambridge Greensand. Specimens 

 (from the Gault of .Puttenham are in the Woodwardian Museum. 



Genus Xanthosia, Bell. 



XiNTHOSIA GIBBOSA, Bell. 



1863. Bell, Monogr. pt. ii, p. 3 & pi. i, figs. 4-6. 



Supplementary. — The resemblance of X. gibhosa with X. granulosa, 

 to which Bell alludes in his description of the latter form, is so 

 close that it may well be regarded as a variety of that species. 

 Almost the only distinctive character refers to the processes of the 

 antero-lateral margin, which in this species are more or less 

 ^pointed, but in X. granulosa are quadrate. The marginal armature 

 is, in all the Brachyura, an unstable character, by reason of the 

 variation in form and in degree of development, according to the 

 age of the individual. I have not been able to detect the puncta- 

 tion of the posterior portion of the carapace which Bell mentions 

 as a character. Portions of the test preserved on the cephalic area 

 of specimens which I have seen are distinctly, but minutely, granu- 

 lated. The fissures in the borders of the orbit are very distinct. 



I have met with no other specimens than those described by 

 Bell, four in number, now in the British. Museum (Cunnington 

 Coll.). The carapace is the only portion that has been determined. 

 The name XantJiosia has been applied by De CandoUe to a genus of 

 Umbelliferous plants. 



Xanthosia granulosa (M'Coy). (PI. II, fig. 5.) 



1854. Beussia granulosa, F. M'Coy, ' Contrib. Palaeont.' p. 272. 

 1863. XantJiosia granulosa, Bell, Monogr. pt. ii, p. 4 & pi. i, fig. 13. 

 1865. Eeussia grcmosa, Milne-Edwards, ' Monogr. Crust. Foss. Fana. Canceriens,' 

 Ann. Sci. Nat. ser. 4, vol. xviii, p. 78 & pi. v, fig. 2. 



Description. — Carapace a third wider than long, depressed. 



