94 



THE FORAMINIFERA 



double row of pores, or, in the " dendritine " varieties, of an 

 opening the margins of which are produced into branched and 

 winding recesses. 



The extent of the septum which forms the terminal face of 

 each chamber, and is perforated by the apertures, varies, of course, 

 with the shape of the chambers, being small and more or less 

 circular in outline in the crozier-shaped forms, and much elongated 



ffiT 



FIG. 29. 



Peneroplis pertusus, Forsk. v l , a common 

 flattened variety ; fl 2 , the crozier-shaped variety 

 (x 2(5). A, central part of section of megalo- 

 spheric form. B, of the microspheric form ; 

 sp.p, spiral passage ( x 280). 



in the flattened forms. In the latter case it is markedly convex 

 when seen from the side. 



In the megalospheric form the size of the oval megalosphere 

 varies in samples from different localities. Thus, in 300 specimens 

 from Aripo, on the coast of Ceylon, I find the average value of 

 M to be 30 p, and it varies in different individuals from 24-42 p. 

 In a batch from Watson's Bay, Port Jackson, the average value is 

 42 p., and the individual variation ranges from 32-59 /z. In two 

 specimens in a West Indian gathering, however, M= 19 and 22 /A. 



A narrow spiral passage leads from the megalosphere and 



