Nomenclature of the Foraminifera. 35 



In some of the figured specimens of O. globularis the not 

 unusual hole in the base is indicated. Occasionally individuals 

 are perforated by a more or less irregular tubular cavity. The 

 roundness of the specimens, and their holes and tubular cavities, 

 appear to have suggested to the old "flint-folk" of the Valley of 

 the Somme that they might be used for beads ; for such perfo- 

 rated Orbitolina are frequent in the gravel that yields the flint 

 axes. 



11. The sinuous superficial mesh-work, formed by the edges 

 of the overgrown septal planes, is a marked feature in the sub- 

 conical Orbitolina from the Lower Cretaceous rock of the Perte- 

 du-Rhone (Aptian) and of Sarthe (Cenomanian), from the Green- 

 sand of Warminster and Haldon Down, and from the Chalk- 

 marl and Chalk (Turonian and Senonian); also in the little 

 globular fossils of the Chalk known as Tragos and Coscinopora 

 globularis, varying from the size of shots to that of bullets ; and 

 when we find a similar structure apparent in the still larger, 

 irregularly rounded, sponge-like fossils accompanying these glo- 

 bular and conoidal Orbitolina in the Chalk, we know not how to 

 separate the several forms, where size and some irregularity of 

 shape appear to be the only distinctive characters. 



The conical, hemispherical, and flattened forms of Orbitolina, 

 so common in the Cretaceous deposits, and known under twelve 

 or more different names, are referable to one specific type, 

 namely the 0. concava, Lamarck, sp. ; and to this type, not only 

 these comparatively large plano-convex and concavo-convex 

 varieties belong, but also the large, limbate, globular forms on 

 one hand, and the small, less limbate, and smooth forms, both 

 round and flattened, recent and fossil, on the other. 



Orbitolina concava, Lam. sp., O. conica, D'Arch. sp. (Mem. Soc. 

 Geol. France, ii. p. 178), and O. conoidea, Gras (Foss. de FIsere, 

 p. 51, pi. 1. f. 4-6), are concavo-convex individuals, more or 

 less thickened, presenting the typical characteristics of the 

 genus, but neither in too simple nor in too exaggerated a con- 

 dition. This variety has been figured by Phillips (Geol. Yorks. 

 pi. 1. f. 11), Woodward (Geol. Norf. pi. 4. f. 9), and Mantell 

 (Foss. S. Downs, pi. 16. f. 22-24), and described as a Lunulite. 

 The typical form (O. concava) is well figured by Michelin, Icon. 

 Zooph. pi. 7. f. 9. 



O. gigantea is a name given by D'Orbigny (Prodrome, ii. 

 p. 279) to a large concavo-convex specimen from Royan, nearly 

 4 inches in diameter. What a contrast to the little recent O. an- 

 nularis and its congeners ! 



12. Faujas's " Numismale " or " Lenticulaire M from Maes- 

 tricht (Hist. Nat. Mont. St. Pierre, p. 186, pi. 34. f. 1-4) is an 

 Orbitolina. This, described and figured by Bronn (Leth. Geogn. 



3* 



