PAEKEKIA 



8I 7 



structure has been elucidated by Mr. H. B. Brady and the Author. 1 

 Geologists who have worked over the Greensand of Cambridgeshire 

 have long been familiar with solid spherical bodies which there 

 present themselves not unfrequently, varying in size from that of a 

 pistol-bullet to that of a small cricket-ball ; and whilst some regarded 

 them as mineral concretions others were led by certain appearances 

 presented by their surfaces to suppose them to be fossilised sponges. 

 A specimen having been fortunately discovered, however, in which 

 the original structure had remained unconsolidated by mineral in- 





FIG. 617. General view of the internal structure of Pnrkeria : In the hori- 

 zontal section, J l , I-, F', 7* mark the four thick layers; in the vertical 

 sections A marks the internal surface of a layer separated by concentric 

 fracture ; B, the appearance presented by a similar fracture passing through 

 the radiating processes ; C, the result of a tangential section passing 

 through the cancellated substance of a lamella; D, the appearance pre- 

 sented by the external surface of a lamella separated by a concentric 

 fracture which has passed through the radial processes ; E, the aspect of a 

 section taken in a radial direction, so as to cross the solid lamellae and their 

 intervening spaces ; c\ c" 1 , c 7 ', c ', successive chambers of nucleus. 



filtration, it was submitted by Professor Morris to the Author, who 

 was at once led by his examination of it to recognise it as a member 

 of the arenaceous group of Foraminifera, to which he gave the de- 

 signation Parkeria, in compliment to his valued friend and coadjutor, 

 Mr. "VV K. Parker. A section of the sphere taken through its 

 centre (fig. 617) presents an aspect very much resembling that of an 

 Orbitolite, a series of chamberlets being concentrically arranged 

 round a ' nucleus ; ' and as the same appearance is presented, what- 

 ever be the direction of the section, it becomes apparent that these 



1 See their 'Description of 1'nrkfi'in and Loftiisia' in Philosophical Trans- 

 actions, 1869, p. 721. Though it appears convenient to allow this description of 

 Parkeria to remain, it must be noted that some of those most competent to judge 

 are of opinion that Parkeria is one of the Stromatoporoids, an obscure and difficult 

 group of fossil Hydroida (see the memoir by Professor Alleyne Nicholson, published 

 in 1886 by the PalsBontographical Society). 



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