PLATE III. 



Fig. 1. ZAPHRENTIS GIGANTEA, Lesueur. A specimen naturally split longitudinally 

 Nat. size. (p. 22.) 



Fig. la. Another example of the same, of the natural size. Both of these figures repre- 

 sent immature individuals. 



Fig. 2. ZAPHRENTIS PROLIFICA, Billings. Nat. size. (p. 23.) 

 2a. Portion of the edge of the calice of the same, enlarged. 



Fig. 3. PETRAIA(?) LOGANI, Nich., viewed from behind. Nat. size. (p. 30.) 



3a. The same, viewed from the front. 



36. Another example, from which the epitheca has been removed, viewed from 



below. 



,3c. Dorsal aspect of another specimen, which has not been exposed to weathering. 

 3d. Outline of another example of the same, showing the sub -triangular form of the 



calice. 

 3g. A few of the septa viewed from the exterior, the epitheca being wanting. 



Enlarged. 

 3/. Transverse section of a fragment, enlarged. 



