568 DR. CARPENTER'S RESEARCHES ON THE FORAMINIFERA. 



dividing cc' and dd' ; these interseptal canals seem to communicate by 

 short lateral twigs with the cavities of the adjacent chambers, whilst at 

 g> g> S^ S tne y become connected with vertical branches, which unite them 

 with those of other planes: at h h, h' h' are seen the canals proper to the 

 annular septa. 



Fig. 12. Thin section of Cydoclypeus, passing through its central plane, showing por- 

 tions of four annul!, 1 1, 22, 33, 44, with the general relations and con- 

 nexions of their chambers, the double septa by which they are separated, 

 and (in parts) the interseptal system of canals: 36 diam. 



PLATE XXX. 



Fig. 1. General view of a disk of Cydoclypeus, showing the aspect of its surface, and 

 the appearances presented by horizontal and vertical sections: 12 diam. 



Fig. 2. Surface-view of a full-grown specimen of Heterostegina, showing its tendency 

 to assume the discoidal form by the opening-out of the spire: a be, the thick- 

 ened margin of the spire; cda, its growing edge or mouth : 10 diam. 



Fig. 3. Monstrous specimen of Cydoclypeus, having a vertical plate superimposed 

 upon the horizontal disk : 5 diam. 



Fig. 4. Ideal figure of a portion of a Cycloclypeus-d'isk laid-open to show the details 

 of its structure: a, a, a, upper stratum, consisting of superimposed tubular 

 laminae; b, b, b, portion of lower stratum ; c, c, c, cones of non-tubular 

 substance, sometimes perforated by larger canals ; d, d, d, their bases pro- 

 jecting on the surface ; e, e, plates of non-tubular substance, continuous 

 with the septa between the chambers ; f,f, passages of communication 

 between the chambers, through the inter-annular partitions, as seen in 

 section ; g,g, the same as seen from the interior of the chambers ; h, h, inter- 

 septal canals cut across ; i, a chamber on the walls of which the system of 

 interseptal canals is represented as fully displayed ; k, k, passage of the 

 principal canals along the line of junction between the roof of the chambers 

 and the vertical septa : 60 diam. 



PLATE XXXI. 



Fig. 1. Section of a young specimen of Heterostegina, taken parallel to the surface, 

 partly through the chambered plane and partly (owing to a slight inequality 

 of the specimen) through the shelly investment of the chambers, the boun- 

 daries of which, however, are still distinguishable, owing to the difference 

 of texture between the shell that covers the chambers and that which unites 

 with the septa : a, first cell ; b, second cell ; c c, first subdivision ; f, second 

 subdivision ; e, e, large passages connecting the chambers that abut on the 

 pre-formed whorl : 60 diam. 



