288 FAMILY XUMMULINIDA. 



cially numerous and varied in the Vienna basin and in the Sub-Apennine strata. The geological 

 distribution of the Kontoniiie sub-type, so far as we certainly know at present, corresponds 

 closely with that of the typical PolptomrJla -. there are, however, some Foraminifera in the 

 Carboniferous Limestone of Russia, described by Eichwald, that very much resemble 

 Konionina. 



GcniisX. — Heterostegina (Plate XIX, fig. 1). 



487. Hlsiori/. — Although the genus Heterostegina was established by RL d'Orbigny in his 

 first systematic arrangement of Foraminifera (lxix), its essential structure was altogether misap- 

 prehended by him, and has been misrepresented by others on his authority. Even in his latest 

 classification (lxxiv) he continued to rank this genus in his order Entomostet/ues, placing it in 

 close approximation to Aiiipliisfegina, from which he considered it to be chiefly differentiated 

 by the subdivision of its principal chambers by transverse partitions. I have had the oppor- 

 tunity of examining, by the kindness of Mr. Cuming, a very extensive series of specimens of 

 this type from the Philippine islands ; many of these are of large size, attaining as much 

 as half an inch in diameter ; and the appearance of the adult specimens scarcely diflers less 

 from that of the young (which latter are alone figured by M. d'Orbigny), than it does in the 

 case of Orbiculiiia. The dredgings of Mr. Jukes have furnished me with numerous specimens 

 of Ilelerosteghui from the Australian coast; these closely correspond with the figures of 

 M. d'Orbigny, being of comparatively small size, and not exhibiting that peculiar mode of 

 development which is characteristic of the adult ; and as the Australian forms correspond 

 precisely with the young of the Philippine, there can be no doubt of their specific identity. 

 I recognise the shells of the same species as almost the sole components of a fossilized deposit, 

 evidently belonging to the Tertiary epoch, which is very commonly met with in Malta in 

 fissures of the rocks, but of which the precise age is uncertain. 



488. Eaier/ird Characters. — The older specimens of Heterostegina (Plate XIX, fig. 1) 

 present a form which, when regular, may be characterised as discoidal, and whicli is almost 

 perfectly symmetrical ; some degree of twisting, however, is almost constant in the larger 

 specimens. There is a large umbilical tuberosity, somewhat excentrically placed, from which 

 the turns of a spire are seen to commence; and the last of these becomes continuous with 

 one part of the margin of the disk {a, b, c), which there possesses a thick and defined border. 

 x\s this spire opens out, however, it becomes thinner and flatter; and this thinning is 

 especially noticeable at that part of tlie margin of the disk [a, J, c) which corresponds witli 

 the opening of the spire. The whole surface of the disk, except the portion which is occupied 

 by the umbihcal tuberosity, is marked by septal bands, which follow one another at very 

 small intervals, and are strongly curved with their convexity anterior. Not unfrequentl)' 

 these bands do not extend continuously across the convolution, but join themselves to otiier 

 bands, so that the chamber included between them is more or less incomplete. Between 

 each septal band and the one whicli succeeds it, the surface is marked by transverse lines. 



