52 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



The mesenchymatous fibers before passing through the septulae traverse in 

 the proximal part only of the zooecia small lateral chambers called dietettae (=pore 



G x 1 00 H x 1 00 1x100 



PIG. 8. Structure of the pleurocyst. 



A. OchetoselJa jacksonica Canu and Bassler, 1917, X 20. The calcification is active around 

 the areolae. 



B. Mucronella ftranulosa, new species, X 20. Granular pleurocyst. 



C. Smittina grandifossae, new species, X 20. Pleurocyst with iuterareolar costules. 



D. E. Smittina angulata Reuss, 1S65, X 20. Porous pleurocyst. In the interior the olocyst is 

 perforated only by areolae (D). 



F. MitcmneUa rariolosa Johnston, 1838, X 20. The pleurocyst is detached from the subjacent 

 olocyst. 



G. Smittina reticuloides, new species, X 100. Tangential thin section in the vicinity of the 

 olocyst. 



H. Smittina reticuloides, new species, X 100. Tangential thin section through the inter- 

 areolar costules. 



I. Hippomenella rotuJa, new species, X 100. Tangential thin section through the pleurocyst. 



chambers of English authors) (fig. 9, C, D) . These structures persist in fossilization 

 only if their walls are thick; they may be discovered by abrasion of the frontal 



