FORAMINIFERA AND RADIOLARIA. 83 



that the outer layer of the test is worn-away, and the ends of the passages 

 then show themselves as pores upon its surface; this appearance, how- 

 ever, is abnormal, the passages simply running from the chamber-cavity 

 into the thickness of its wall, and having (so long as this is complete) no 

 external opening. This ' labyrinthic ' structure is of great interest, from 

 its relation not only to the similar structure of the large Fossil examples 

 of the same type, but also to that which is presented in other gigantic 

 Fossil arenaceous forms to be presently described. 



477. Although some of the Nautiloid Lituolce are among the largest 

 of existing Foraminifera, having a diameter of 0.3 inch, they are mere 

 dwarfs in comparison with two gigantic Fossil forms, whose structure 

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



Fio. 323. 



General view of the internal structure of ParJceria : In the horizontal section, I 1 , P, P, V, 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 radiat- 

 ing processes; c, the result or a tangential section passing through the cancellated substance of a 

 lamella; D, the appearance presented by the external surface of a lamella separated by a concen- 

 tric 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 1 , c 2 , c 3 , c 4 , succes- 

 sive chambers of nucleus. 



who have worked over the Greenland 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 fossilized Sponges. A specimen having been fortu- 

 nately discovered, however, in which the original structure had remained 

 unconsolidated by mineral infiltration, it was submitted by Prof. Morris 

 to the Author, who was at once led by his examination of it to recognize 

 it as a member of the Arenaceous group of Foraminifera, to which he 

 gave the designation Parkeria, in compliment to his valued friend and 

 coadjutor, Mr. W. K. Parker. A section of the sphere taken through its 

 centre (Fig. 323) presents an aspect very much resembling that of an 



1 See their ' Description of Parkeria and Loftusia,' in "Philosophical Trans- 

 actions," 1869, p. 721. 



