Vol. 54. J THE DECAPOD CKTJSTACEA OP ENGLAND. 39 



that of X. granulosa^ except as regards the granulation of the 

 cephalic portion of the dorsal surface ; this area, instead of being 

 uniformly and minutely granulated as in X. granulosa^ bears larger 

 and pointed tubercles, which vary considerably both as to size and 

 arrangement — not being disposed in any constant order, but scat- 

 tered irregularly over the gastric and hepatic lobes, differing in 

 disposition in each individual. The cephalic lobes are more inflated 

 and more prominent than in X. granulosa. The antero-lateral 

 border is so compressed as to be rendered trenchant. 



Length of carapace = 11 to 16 mm. ; width = 18 to 28 mm. 



Affinities. — X. similis is smaller in size than its congener — 

 X. granulosa — and has a general aspect which suggests the proba- 

 bility that it may be an abnormal form of that species. It was 

 first recognized by BeU, who referred it to the genus Etyus, but 

 well-preserved specimens present characters so completely identical 

 with those of XantJiosia that I do not hesitate to transfer it to that 

 genus. The difference in form, the irregularity of the granulation of 

 the carapace, and the compressed, trenchant, antero-lateral margin, 

 at once distinguish it from Etyus Martini. 



The posterior portion of the carapace figured by Bell (pi. xi, 

 fig. 15) is broken away, so that it is made to appear dispro- 

 portionately wide. 



Distribution. — Cambridge Greensand. I have examined alto- 

 gether about twenty specimens, which are preserved in the British 

 and Woodwardian Museums, and in my own collection. This species 

 is probably represented in the Gault of Sainte-Croix by X. Fischeri, 

 Milne-Edwards. 



Genus Xanthopsis, M'Coy. 



The diagnosis of Xanthopsia is given by Bell in detail amply 

 sufficient for determination. It may be added that the sternal 

 plastron is broadly ovate and a fourth longer than wide. Genital 

 pores exist in the third segment of the female. The episternum is 

 half the width of the sternum and twice as wide as long. As 

 regards the abdomen, it is difficult to determine whether the middle 

 segments in the male were free or coalescent during life ; but 

 transverse markings distinctly indicate the seven normal segments. 

 The chelae are unequal, and in some examples the difference in 

 size is very considerable — one being only a third as large as its 

 fellow. The fingers of the larger claw are robust, and have the 

 dentary margin coarsely tuberculated ; those of the small chela are 

 slender and usually nearly edentulous. A similar difference occurs 

 normally in many other genera, both recent and fossil. 



Xanthopsis is abundantly represented in the Tertiary deposits by 

 a variety of forms, of which 14, including 10 foreign, have been 

 described as distinct species. Milne-Edwards has expressed an 

 opinion that several of the foreign forms, to which specific names 

 have been applied, can be considered as varieties only ; Bell's 

 careful investigations led him to a similar conclusion relative to 



