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DR. carpenter’s RESEARCHES ON THE FORAMINIFERA. 
ton and of a canal-system between the contiguous walls of adjacent chambers, and in 
the minutely-tubular structure of the shell, — all of them points of high physiological 
importance, — Cycloclypeus differs entirely from Orbitolites, and agrees with Nummu- 
Iftes ; whilst it agrees with Orbitolites, and differs from Nummulites, in the single 
circumstance that its mode of increase is cyclical instead of helical, — a difference 
which we have seen to present itself at two different periods of life of the very same 
specimens of Orbitolites and Orbiculina, and which must, therefore, be a character of 
quite subordinate importance. 
Genus Heterostegina. 
111. The correctness of the views just advanced is fully borne-out by the occur- 
rence of a type, which bears precisely the same relation to Cycloclypeus, that Orbicu- 
lina bears to Orbitolites-, one, namely, in which — the form and connexions of the 
individual chambers, the minute structure of the shell, and the distribution of the 
canal-system, being essentially the same — the plan of growth is helical, at least 
during the earlier period of life. This is the case with the genus Heterostegina, 
which was established by M. d’Orbigny in his memoir of 1825, but the essential 
structure of which he has altogether misapprehended. In his latest classification of 
the Foraminifera*, he ranks this genus in his order Entomostegues, which is com- 
posed of Foraminifera, whose segments are disposed in a spiral, but in two different 
planes alternating with each other, so as to render the entire shell inequilateral. 
Of the genus Heterostegina, which he ranks in close approximation to Amphistegina, 
he gives this definition: — “ Coquille a spire embrassante, dont les loges sont sepa- 
rees interieureraent par des cloisons transversales.” Now in the first place, I am 
quite satisfied that the chambers of Heterostegina do not alternate one with another, 
but are arranged in one plane about the same axis, as is shown in figs. 1, 7, Plate 
XXXI.; and secondly, it gives by no means a correct idea of its strueture, to liken its 
chambers to those of Amphistegina save for their division by transverse partitions. 
112. I have had the opportunity of examining, by the kindness of Mr. Cuming, a 
very extensive series of specimens of this genus (belonging, apparently, to the species 
H. costata, D’Orb.-I-), 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 speci- 
mens scarcely differs less from that of the young (which latter are alone figured by 
M. d’Orbigny), than it does in the case of Orbiculina. The dredgings of Mr. Jukes 
have furnished me with numerous specimens of Heterostegina from the Australian 
coast ; these closely correspond with the figures of M. d’Orbigny, being of compara- 
tively small size, and not exhibiting that peculiar mode of development which is 
characteristic of the adult. 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, 
* Cours ^lementaire de Paleontologie, tom. ii. p. 201. f Foram. Foss, de Vienne, p. 212. 
