304 FAMILY NUMMULINIDA. 



canal-system. Of all existing Foraminifera, Thioporus most approximates Orbifoides in the 

 structure of its superficial laminae, as Cyclocli/peus does in that its median plane. 



509. Geolopcal Distribution, — This genus seems to have made its first appearance in the 

 Maastricht Chalk, but to have been more fully developed in association with Nummulina in 

 most of the localities in which that type attained its extraordinary predominance at the com- 

 mencement of the Eocene period. Its smaller forms, chiefly belonging to the species 

 0. Fortisii, present themselves abundantly in the Nummulitic limestone of the Western 

 Pyrenees, in that of Northern Italy, and in that of the borders of the Black Sea ; the larger 

 and more developed examples of both species occur intermingled with Nummuhtes and 

 Orbitolites in Scinde and other parts of northern India ; but this tj^pe is found in the 

 greatest abundance in the American Continent, the so-called " Nummulite limestone " of 

 Alabama, which extends over an immense area in that state, being almost entirely made up 

 of the remains of 0. Mantelli. It occurs also in Madagascar, and is abundant in Jamaica, 

 where it is associated with Nummulites. 



Genus VIII.— Fusulin.a. (Plate XII, figs .24—29). 



510. History. — The genus Fiisulina was instituted in 1829, by Fischer de Waldheim 

 (■ Oryctograph. Moscou,' p. 126), for the reception of a group of fusiform Foraminifera 

 occurring in sreat abundance in the white Carboniferous Limestone of Russia. It was first 

 adopted by D'Orbigny, in his palaeontographical contribution to Sir R. Murchison's ' Geology 

 of Russia,' and was subsequently associated in his systematic treatises (lxxiii, lxxiv) with 

 Nonionina and Nujumulina, to which he stated it to correspond in its single median fissured 

 aperture, and in the absence of subdivision in its chambers, notwithstanding the close approxi- 

 mation which its form presents to that of Alveolina. By Prof. Ehrenberg, on the other hand, 

 the most elongated forms of Ftisiilina were described and figured (xlii) under the name of 

 Alveolina, whilst to the more globular forms he gave the name BoreJis, which he adopted 

 from Montfort (^ 146) ; though it is not a httle singular that among the specimens which he 

 figured are internal ' casts ' which very clearly indicate the Nummuline affinities of this 

 type. Messrs. Parker and Rupert Jones (lxxx a) have associated Alveolina and Fusvlina as 

 allied, if not identical generic forms ; but in so doing they have been misled, as I conceive, 

 by a resemblance which is certainly more striking than D'Orbigny recognised between the 

 plans of growth of these two types ; whilst they have not given what I consider to be 

 adequate value to the essentially Nummuline character of the aperture, which will be found 

 to harmonise with the best information I have been able to obtain respecting the texture of 

 the shell. 



511. Eaiernal Characters. — The ordinary form of Fi(sulina, well expressed by its name, 

 bears a very close general resemblance to that of Alveolina (^ 147) ; and, as in that genus, we 

 find that it may, on the one hand, be elongated into a cylinder, or, on the other, be shortened 

 to a prolate spheroid. The F. hjperbona of Salter ('Belcher's Arctic Voyage,' 1855, vol. ii. 



