TWO GIGANTIC TYPES OE ARENACEOUS EORAMINIEERA. 
725 
2. General Characters . — In the two specimens which retain their original Arenaceous 
condition, the sphere, when laid open, is seen to be formed of a series of concentric layers 
(Plate LXXII.), composed of lamellae of ‘labyrinthic structure’* *, partially separated 
by concentrically disposed interspaces, but connected at intervals by ‘ radial processes ’ 
which consist of large tubes that are surrounded (in all except the five or six innermost 
layers) by labyrinthic structure resembling that of the concentric lamellae. As every 
part of the fabric is made up of sand-grains cemented together, it is very easily cut by 
a fine saw in any direction, so as to display in section the general structure and arrange- 
ment of the arenaceous framework. As such sections, however, are very friable, they 
cannot be made transparent enough to exhibit the details of their structure, except by 
cementing them to glass with hard Canada balsam (which should be made to penetrate 
them thoroughly), and grinding them down after having been thus solidified ; and the 
specimens thus prepared are by no means equal to transparent sections of the best 
infiltrated specimens (§§ 3, 13). But some of the most valuable information afforded 
by non-infiltrated specimens is to be obtained from the examination of fractured sur- 
faces ; the concentric lamellse being readily separable from one another by the intro- 
duction of a knife-blade into the interspaces. It has been by combining the information 
obtained through both these methods, that my able draughtsman, Mr. A. Hollick, 
has constructed the ideal representation given in Plate LXXII. f; which brings together 
in their actual relations the surfaces obtained by section and by fracture, which are sepa- 
rately represented on a larger scale in Plates LXXIII. and LXXIV. ; — exactly as they 
would be seen if it were possible to remove just those portions of the fabric (and no more) 
whose absence is necessary to disclose them. 
3. In a second set of specimens, the original Arenaceous framework has been entirely 
consolidated by mineral infiltration, which has completely filled all its vacuities : the 
infiltrating material is usually calcareous ; but in one remarkable specimen belonging 
to the Museum of Practical Geology in Jermyn Street (which I have been enabled to 
variations. On communicating with him on the subject, I have received from him a ready acquiescence in the 
Generic designation above proposed ; whilst, at the same time, he prefers to reserve the publication of the 
results of his own studies of this type, until after the appearance of my description of it. The series of speci- 
mens contained in the Woodwardian Museum presents a very considerable diversity of external forms ; but so 
far as I have had the opportunity of examining their internal structure, their agreement with the globular type 
on which my own description is based is so complete, as to lead me to regard that diversity as a mere varietal 
modification. 
* The term labyrinthic structure has been used in my ‘ Introduction to the Study of the Eoraminifera ’ to 
denote an irregular aggregation of minute chamberlets freely communicating with each other ; such as would 
be produced by the more or less complete subdivision of a principal chamber by the growth of partitions inter- 
secting one another in various directions, — as often happens, for example, in the Arenaceous genus Lituola (op. 
cit. § 214). This kind of structure presents a considerable resemblance to that which, in the Anatomy of higher 
Animals, is termed * cancellated.’ 
t Such ‘ built-up ’ figures were very successfully designed by my former draughtsman, Mr. George West, 
in his admirable illustrations to my previous Memoirs on this group. 
