440 Mr. H. J. Carter on the 



illustrations of the structure of the genus, taken from Orhi- 

 toides media ^ d'Orb., of 1847, olim Orhitolites media, d'Ar- 

 chiac, of 1837,= Orhitolites of Faujas de Saint-Fond in 1799, 

 may be found in his ' Cours de Paleontologie et de G^olog-ie ' 

 (vol. ii. pp. 19.3, 194) and ' Prodrome ' (vol. ii. p. 279), where 

 he has also assigned to them as their existence in time the 

 geological interval between his " Senonien ■" and " Parisien " 

 divisions^ that is between the Upper Chalk and the Nummulitic 

 series inclusively. 



Now this would probably be quite sufficient if the struc- 

 tural type of Orhitoides media was the same as that of all 

 the other species ; but this is not the case, inasmuch as the 

 structural type of Orhitoides impyracea, which d'Orbigny has 

 placed in his " Suessonien "" division of the Eocene Period 

 \op. cit. vol. ii. p. 732), is markedly different. 



The typical structure of Orhitoides media^ d'Orb. (making 

 allowance for the diagrammatic nature of his illustrations), is 

 precisely like that of Nummidites ManteUi, Morton, of the 

 Claiborne Beds in Alabama, saving the presence of the super- 

 ficial layer in the latter and the difference in the marking of 

 the surface in the former, as will be more particularly seen 

 hereafter when I come to describe the type forms of these 

 fossils respectively, while the structure of Orhitoides papi/- 

 racea is almost precisely like that of Lycophris ephipyium 

 delineated by J. de C. Sowerby in his illustrations of Grant's 

 " Memoir of the Geology of the State of Cutch, in Western 

 India ^' (Trans. Geol. Soc. Lond. 1840, 2nd ser. vol. v. 

 pi. xxiv. figs. 15 a and 15 h). D'Orbigny's genus, then, dates 

 from 1847 and Sowerby 's from 1840. 



Here it should be remembered that Sowerby's illustrations 

 of the structure of his Lyc,oi)hris ephipjnum (viz. pi. xxiv. 

 figs. 15a and Ibh) are very different from those of his 

 Lycophris dispansus close by (viz. 16 a and 16 J), as in 

 his " fig. 16 a " there are none of the columns which are so 

 characteristic of his L. ephipipiwni in " fig. 15 ^," and the 

 columns indicated in the section of L. dispansus, fig. 16 5 

 (since the chambers of the central plane are not shown), may 

 or may not be those of the ephippial type, as will be seen 

 hereafter, although I confess to a leaning towards the latter. 

 Sowerby also, in adverting to his illustrations in the para- 

 graph following his explanations, states that " possibly these 

 two forms may be different stages of the growth of the same 

 species." I mention this here to point out that, although the 

 presence of the " columns " is a persistent character of those 

 Orhitoides which present the structural ty])e of Lycophris 

 ephippium, it is by no means so in that of Orhitoides media, 



