1869.] 



two gigantic Types of Foraminifera. 



403 



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 only filled the chamberlets of the preceding layer, 

 but projected beyond it ; that the radial processes were first built up like 

 the columns of a Gothic cathedral, and that their impervious invest- 

 ing 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 con- 

 veyed to the outer surface of that floor through the radial tubes. The 

 author further argues, from the analogy of living Foraminifera, that not- 

 withstanding 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 lamellae, 

 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 ex- 

 tremely 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 Classifi- 

 cation already referred to. This difference is indicated by its shape, which 

 closely resembles that of many Alveolince and Fusulince ; being a long oval, 

 frequently tapering almost to a point at either end, though sometimes 

 obtusely rounded at its extremities. 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 produced if one of the 

 simple Rotalians were thickened and drawn out at the umbilici. The space 

 inclosed by the primary lamina is divided into chambers by longitudinal 

 septa, which may be regarded as ingrowths from it, extending, not perpen- 

 dicularly (as in Alveolina), but very obliquely. The chambers, sepa- 

 rated by these principal or secondary septa, are long and very narrow, 

 and extend from one end of the body to the other. Their cavities are 

 further divided into chamberlets by tertiary ingrowths, which are gene- 



