24 FORAMINIFERA OF THE CRAG. 



type) layers of chambers. Pseudopodial orifices situated in depressions on the lateral face 

 of the external annular chamber. In the simple type, consisting of a single row of pores, 

 there is one pore in each depression ; in the complex type several rows, roughly corre- 

 sponding to the number of layers of chambers. Diameter, j'^th inch to 1 inch. 



As the variations from the typical form are so unimportant that subdivision 

 is unnecessary, little need be added in respect to the species, not already given in the 

 generic distinctions. Ehrenberg rightly referred his " Sorites " (a simple Orbitolite) to 

 the N. orbiculus, of Forskal, whose description of it embraces also " Amphisorus " (com- 

 plex in growth). 



We have seen but one or two perfect specimens of Orbifolites orbiculus from the 

 Crag (Sutton), and these have been imbedded in a hard matrix ; but we have a few fragments 

 separated from the rock. Our figure, Plate III, fig. 45, is taken from one of these frag- 

 ments ; and figures 46 and 47 illustrate the stracture of the complex type, the one being 

 a view of a portion of the edge of a specimen, showing the pseudopodial apertures ; the 

 other a vertical section, exhibiting the arrangement of the chambers, and their connection 

 with each other. 



The distribution of OrbitoUtes is almost confined to tropical latitudes, its range 

 extending but little into the seas of the temperate zones. On the Australian shores, in the 

 Indian Ocean, and in the Caribbean and Red Seas, it is, perhaps, most abundant. It 

 exists in the Mediterranean. Fossil specimens are first found in the Maestricht Beds 

 (0. macropora), and it reaches its maximum abundance in the Calcaire grossier of the 

 Paris Basin. It is also found in the Bracklesham beds of Hampshire. 



Alveolina, sp. 



We may notice, in passing, the occurrence of one or two somewhat obscure specimens 

 of Alveolina that we found in the Bryozoan Crag of Sudbourne. They have been un- 

 fortunately lost. These were so worn and devoid of character as scarcely to admit of 

 specific determination ; their presence, however, is of interest in connection with that of 

 some other species which may have been derived from earlier Tertiary formations. 



