GENUS TINOPOEUS AFFINITIES. 
561 
niimerous large pseudopodian foramina*. This relationship is admitted hy Messrs. 
Paekee and Rupeet Jones; who state, however, that Planorhulinw are differentiated 
by having “ two or three tubular and margined apertures to each chamber, coarser 
pseudopodial pores, and no umbilical cells.” Now I have shown that every chamber in 
the adult is connected with its adjacent chambers of the same or of alternate planes by 
two apertures ; so that at the free growing margin of the young disk there would pro- 
bably be at least two such pairs of apertures in the wall of every chamber. The 
difference in the size and number of pseudopodian pores is a very trivial character. 
And the superposed umbilical cells will probably be absent in the young Tino])orus, 
when as yet only a small number of rows of chambers have been formed around the 
central cell. I have, in fact, specimens in my possession which would be unhesitatingly 
characterized as Planorbulince by such as are unacquainted with the structure of the 
type we are considering ; yet which I cannot help regarding as in all probability young 
forms of Tinoporus^ having been found in the same dredging, and presenting just the 
characters which I should expect from analysis of the structure of the adult to find in 
them. Moreover, I have Planorbulince whose early growth is so distinctly spiral as to 
correspond in every essential particular with the young of Potalia. 
218. It is not a little remarkable, however, that this organism should also be very 
closely related to a body of which the true nature has hitherto been doubtful, viz. the 
Millepora rubra of LAMAECKf, the Polytrema miniacea of BlainvilleJ. This grows 
parasitically upon shells, sometimes spreading over their surface in a laminated form, 
sometimes rising into a sort of stem and sending off branches. I have ascertained by 
examination of thin sections, that it is composed of minute chambers piled together very 
much in the manner of those of Tinoporus, and having the same kind of communica- 
tions ; and as Mr. Paekee has in his possession a specimen of a nearly globular form, 
attached to a projection of a bivalve shell, it may be questioned whether the difference 
between the two organisms is even of specific value. For the mode of growth which 
ordinarily characterizes each, shows a tendency to pass into that of the other ; Tinoporus 
Icevis occasionally flattening itself out and extending marginally, whilst Polytrema 
miniacea occasionally restricts itself within a compact spheroidal form. The probable 
relationship of Polytrema miniacea to the Foraminiferous type has been already 
suggested by the sagacity of Dr. J. E. Geay § ; but as he was not acquainted with the 
internal structure either of Tinoporus or of Polytrema, he could not make a more 
particular approximation. I should add that the bodies described and figured by 
Professor Max. Schultze || under the generic name of Acermilina appear to me to belong 
to the same type. I have in my possession a specimen growing round the stem of a 
♦ See Professor "Williamsox’s Monograph of the Eecent Foraminifera of Great Britain, p. 57. 
t Hist. Nat. des Animaux sans Vertebres, troisieme edit., tom. ii. p, 309. 
f Manuel d’Actinologie, p. 410, pi. 69. fig. 16. 
§ Proceedings of the Zoological Society, April 27, 1858. 
11 liber den Organismus der Polythalamien, p. 67, plate 6. figs. 12-15. 
MDCCCLX. 4 E 
