70 Transactions of the Royal Microscopical Society. 



has to Coi'iiuspira and SjpirilUna.* With its great size, it has 

 considerable labyrinthic extension of its shell walls within, as in 

 Lituola. The great spherical FarJceria is sandy with little cement, 

 and, beyond the nucleus of earliest chambers, its walls (highly 

 labyrinthic and Lituoline) are quite concentric and enclosing, un- 

 like any otLer known Foraminifer.f 



In ValvuUna we have a linking between the Perforata and 

 the Imperforata ; and if ValvuUna leads to Trochammina and 

 Wehhina, and if these, when poor in sand-grains, are but little 

 distinguished from Nuhecularia, Cornuspira, and Miliola (most 

 of which also can at times take up sand into their shellsubstance), 

 there are evidently several points where the differentiation of the 

 three great Foraminiferal groups is by no means absolute. 



Shells of the Perforate or Hyaline Foraminifera. — The 

 globular, subglobular, lageniform, and other primordial segments, 

 whether simple, or divided off into a secondary semilune, are seen 

 in the Imperforata, Arenacea, and Perforata. The straight, linear, 

 or " stichostegian " growth of segments occurs in all the three 

 groups, though rare in the first, where it is represented only by 

 some attenuate Articulin^ and Spirolinoe, with obsolete Milioline or 

 Peneroplid commencements. In the second and third groups it is 

 common, as in Lituolee and Nodosari^. It often occurs too as a 

 " sport," or wild growth, after other segmental arrangements, 

 giving rise to " dimorphous " Miliolpe, Peneroplides, Cri stellar i^e, 

 Polymorphinse, Virgulinse, and Textularise. Both Lituola and 

 Nodosaria (theoretically straight, but often bent), are so changeable 

 that dimorphism of curved and straight (lituate), or of square- 

 ness and roundness, in the same individual, is not unfrequent. The 

 only analogous freedom from the restraint of a regular fixed line 

 of growth among the Glohigerinida is enjoyed by Planorhulina, 

 especially in its Truncatuline modifications ; but here a single 

 straight line is never attained. The heaping up of chambers and 

 chamberlets, as in Orhitoides, Patellina, Eozoon, and others of the 

 Glohigerinida, is not here in question. 



The existence of " canal-system " and " intermediate skeleton " 

 is characteristic of the higher Rofalina, but it has been discovered 

 in Planorhulina by M. Munier-Chalmas.t 



The simple, tubular, coiled Cornuspira, Trochammina (T. in- 

 certa), and Spirillina are scarcely distinguishable except by their 

 shell-texture; and though some fossil (Jurassic) Cornuspirai and 

 Trochammime are so thin, and in the latter case so free from sand, 

 as to be subtranslucent, their habit of growth distinguishes them ; 

 whilst Spirillina is always perforate. 



Alveolina, Loftusia, and Fusulina represent, in the three several 



* H. B. Brady, ' Thil. Trans.,' 1869, pp. 741 and 751. 



t Carpenter, op. cit., p. 728. 



X 'Annals Nat. Hibt.,' ser. 4, vol. xiii., p. 459, nvte. 



