92 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 21, 



The specimen was obtained from a mass of quartzite, and rests 

 enclosed in a portion of the body- chamber of a Nautilus im/perialis. 



2. Rhachiosoma echinata, sp. nov. (Plate IV. fig. 5.) 



This handsome crustacean, which must have measured 85 inches 

 from tip to tip of its lateral spines, and 1| inch from the anterior 

 to the posterior border of its carapace, is far more robust than the 

 preceding species. The hepatic spines are only 5 an inch in length, 

 and develope a smaU branch spine midway upon their anterior 

 border, resembling in this character the hepatic spines of Psammo- 

 carcinus Hericartii (see Plate IV. fig. 4). 



The arrangement of the tubercles agrees with that in the foregoing 

 species {R. bispinosa), save that around the central tubercle on the 

 cardiac region there are placed three very minute tubercles, whilst 

 two others, equally minute, mark the metacardiac region. The latero- 

 anterior border gives evidence of three marginal spines on either 

 side, all of which, however, have been broken off. The frontal 

 border is quite lost, although most carefully attempted to be worked 

 out by an experienced hand ; the extreme hardness of the matrix (a 

 fine-grained and very hard quartzite), as in the former case, 

 defying development. Where the surface of the carapace has been 

 preserved it is finely punctate. The chelate fore-hand is preserved 

 on the right side, exhibiting 3 joints, and measuring about 1| 

 inch in length. 



EXPLANATION OF PLATE IV. 



Fig. 1 a. Dorsal aspect of carapace of Valceocorystes glabra, H. Woodw. (nat. 



size), from the Lower Eocene, Portsmouth. 

 Fig. 1 h. The same, seen from the miderside : on. maxillipede ; br. branebiostegal 



piece. 



From the Cabinet of Caleb Evans, Esq., F.Gr.S. 



Fig. 2. Palmocorystes {Notopocorystes) Millleri, Binkh. (two-tbirds natural size), 

 from the Uppermost Chalk, Maestricht. (Copied from tab. is. fig. 1 b, 

 Mon. des Gasteropodes et des Cephalopodes de la Craie Sup^rieure 

 de Limbourg, by J. Van den Binkhorst, 1861 ; figured for com- 

 parison with P. glabra.) 



Fig. 3. Ehachiosoma bisfinosa, H. Woodw. (nat. size), from the Lower Eocene, 

 Portsmouth. 



From the Cabinet of C. J. A. Meyer, Esq., F.G-.S. 



Fig. 4. Psammocarciiius Hericartii, Desmar., sp. (twice nat. size), from the Sables 

 de Beauchamp (Lower Eocene). (Copied from the Hist, des Crus- 

 taces Podophthalmaires Fossiles , by Alpli. Milne-Edwards, tome i. 

 pi. 10, fig. 1. Paris, 4to, 1861). 



Fig. 6. Ehachiosoma echinata, H. Woodw. (nat. size), from the Lower Eocene, 

 Portsmouth. 



From the Cabinet of C. J. A. Meyer, Esq., F.G.S. 



3. On the Chalk of the Cliees from Seafokd to Eastbotjkne, Sussex. 

 By W. Whitakee, Esq., B.A. (Lend.), F.G.S.* 



* This paper has been withdrawn by the author by consent of the Council. 



