METOPASTER UNCATUS. 47 



Dimensions. — In the example figured on PI. XII, fig. 2 a, the major radius is 

 27 mm. and the minor radius about 19 mm., the thickness of the margin 10 mm. 



Locality and Strafigraphical Position. — The figured example is from the Upper 

 Chalk near Bromley. A number of other examples of this species are in the 

 collection of the British Museum, all from the Upper Chalk, and most of them 

 from the same locality, the locality of the remainder being not recorded. 



Remarks. — I was at first somewhat in doubt as to whether to rank tliis form 

 as a variety of Metopaster Farldnsoni, or as a distinct species. I have taken 

 the latter course. Although there are many points of resemblance in general 

 structure, as well as in various details when considered independently, the facies 

 of this form is so distinct from that of Metopaster Parhinsoni, and is so readily 

 recognisable, that there seems to me full justification for considering Mctupaster 

 zonati's specifically distinct. The great breadth of the supero-marginal plates as 

 compared with their length, the form and character of the ultimate plates, the 

 great thickness of the margin, and the relative proportions of the marginal plates, 

 as well as the general habit of the abactinal surface, apart either from the 

 individual characteristics of the plates independently or from other special details, 

 are amply sufficient to distinguish the form from its nearest ally, Metopaster 

 Parkinsoni. 



5, Metopastee unoatus, Forbes, sp. PI. XI, figs. 3 o, 3 6 ; PL XIV, figs. 1 a — 3 ; 



PI. XV, figs. 1 a, 1 h. 



GoNiASTEE (GoNiODlscus) UHCATU8, Forbes, 18-tS. Memoirs of the Geological 



Survey of Great Britain, vol. ii, 

 p. 4.72. 



— — — Forbes, 1S50. In Dixon's Geology and 



Fossils of the Tertiary and Creta- 

 ceous Formations of Sussex, London, 

 4to, p. 331, pi. xxi, fifjs. 4, 5, 8. 



— — — Morris, lS5-t. Catalogue of British Fossils, 



2nd ed., p. 81. 

 AsTHOOONTUM xmCATTJM, Dujardin and Htipf, 18G2. llisl. Nat. Zoopb. 



Eehin. (Suites a Buffou), p. 399. 

 GoNiASTEB (GoNiODiscus) UNCATUS, Forbes, 1878. In Dixon's Geology of Sussex 



(new edition, Jones), p. 305, pi. xxiv, 



figs. 4. 5, 8. 



