Messrs. Carpenter and Brady on Parkeria and Loftusia. 463 



with it by its radial processes) by a system of cavities, which are 

 in free communication with each other, and which may be collec- 

 tively designated the "interspace-system;" anil from this system 

 the labyrinthic structure of the investin"; lamella is entirely cut off 

 by an impervious wall, which bounds it upon its inner side ; whilst its 

 chamberlets open freely upon the outer side of the lamella, into 

 what, when it is newly formed, is the surrounding medium, but, 

 when it has itself been invested by another layer, into its " interspace- 

 system." — In the larger of the two non-infiltrated specimens which 

 have furnished the materials for the present description, the number 

 of concentric layers is 40, and their average breadth about l-65th 

 of an inch. 



The Author discusses the mode in which this composite structure 

 was formed ; and comes to the conclusion that the production of 

 each new layer was probably accomplished by the instrumentality 

 of the sarcodic substance, which not oidy filled the chamberlets of 

 the preceding layer, but projected beyond it — that the radial pro- 

 cesses were first built up like the columns of a Gothic cathedral, 

 and that their impervious investing wall spread itself from their 

 summits, so as to form a continuous lamella over the sarcodic 

 layer, in the manner that the summits of such columns extend 

 themselves to form the arched roof of the edifice — and that, on the 

 floor of the new layer thus laid, the partitions of the chamberlets 

 were progressively built up by the agency of the sarcodic substance 

 conveyed to the outer surface of that floor through the radial tubes. 

 The author further argues, from the analogy of living Foraminifera, 

 that notwithstanding the indirectness of the communication between 

 the cavitary system of the inner layers and the external surface, 

 the whole of that system (consisting of the labyrinthic structure of 

 the successive lamellge, and of the interspaces which separate them) 

 was occupied during the life of the animal by its sarcode-body. 



The plan of growth in Loftusia is stated by Mr. Brady to differ 

 extremely from that of Parkeria, whilst its intimate structure, on 

 which its physiological condition must have depended, is essentially 

 the same — thus affording a conspicuous example of the validity of 

 the principle of Classification already referred to. This difference is 

 indicated by its shape, which closely resembles that of many Alveolinee 

 and Fusulince, being a long oval, frequently tapering almost to a 

 point at either end, though sometimes obtusely rounded at its ex- 

 tremities. Of two large and perfect examples in the collection of 

 the late Mr. Loftus, one measures 3| inches by 1 inch, the other 

 2^ inches by 1| inch. A transverse section at once indicates that 

 the plan of growth is a spiral, formed by the winding of a continuous 

 lamina around an elongated axis, the general disposition of the 

 chambered structure being very similar to that which would be pro- 

 duced if one of the simple Jiotalinas were thickened and drawn out 

 at the umbilici. The space enclosed by t\\^ primary lamina is divided 

 into chambers by longitudinal septa, which may be regarded as in- 

 growths from it, extending, not perpendicularly (as in Alveolina), 



