462 Royal Society : — 



inch to about \\ inch. The character of their external surface differs 

 considerably in different individuals ; but the Author gives reason 

 for believing that it was originally tuberculated, like a mulberry, and 

 that the departures from this have been the result of subsequent 

 abrasion. The entire sphere is composed of a great number of con- 

 centric layers, all of which, except the innermost, are arranged with 

 very considerable regularity around a central "nucleus," which con- 

 sists of five chambers, disposed in rectilineal sequence, thus unmis- 

 takably indicating the Forarniniferal character of the organism, 

 which might otherwise have remained in doubt, on account of the 

 entire divergence from any known type presented in the structure of 

 the concentric layers. The first of these layers is moulded (as it 

 were) on the exterior of the nucleus, and partakes of its elongated 

 form ; but the parts of every additional exogenous layer are so ar- 

 ranged as to bring about a gradual approximation to the spherical 

 form, which is afterwards maintained with great constancy. Each 

 layer may be described as consisting of a lamella of " labyrinthic 

 structure " (that is, of an assemblage of minute chamberlets, whose 

 cavities communicate freely with one another), separated from the 

 contiguous lamellae by an " interspace," which is traversed by 

 " radial tubes " that pass from each lamella to the one external to 

 it. All these structures, in common with the chamber-walls and 

 septa of the "nucleus," are built up by the aggregation of sand- 

 grains of very uniform size. These sand-grains are found to consist 

 of phosphate of lime ; and they seem to be united by a cement 

 composed of carbonate of lime, which was probably exuded by the 

 animal itself. Although there is a very general uniformity in the 

 thickness of the successive layers, the proportion of their several 

 components varies considerably in different parts of the sphere. In 

 those which immediately surround the nucleus, the solid lamellae, 

 which are composed of labyrinthic structure, are comparatively thin ; 

 whilst the interspaces which separate them from one another are 

 very broad, so that the radial tubes which traverse these interspaces 

 are very conspicuous. As we pass outwards, we find the labyrinthic 

 lamellae increasing in thickness, whilst the breadth of the interspaces 

 diminishes in the same degree, until we meet with layers in which 

 the interspaces are almost entirely replaced by labyrinthic struc- 

 ture. With this increased development of the labyrinthic structure 

 in the concentric lamellae themselves, we find it extending between 

 one lamella and another, as an investment to the radial tubes — thus 

 forming "radial processes" of a subcorneal form, which occupy 

 a considerable part of what would otherwise be the interspaces 

 between the successive lamellae. Still every lamella is separated 

 from that which invests it (except where brought into connexion 



of Wight, which is not less than 2\ inches in diameter. It is interesting to 

 remark that the " nucleus " of a smaller specimen from the same locality con- 

 sists of a considerable number of chambers arranged in a spire, the structure of 

 its concentric spherical layers being exactly the same as in the specimens described 

 in the text. 



