754 SYSTEMATIC PALEONTOLOGY 



four costae (third cycle) ; the four bifurcate about 1 mm. from the center 

 and produce eight costae (fourth cycle) ; and the eight bifurcate 1.5 mm. 

 to 2 mm. from the center, producing sixteen costse (fifth cycle) ; in the 

 last cycle the bifurcations producing the two outer and the two middle 

 pairs of the group take place nearer the center than do those of the other 

 four pairs ; in the largest specimens the pairs of costse in the last cycle are 

 2.5 mm. to 3 mm. long. The ends of the costae are prow-like, but scarcely 

 project beyond the edges of the septa. The intercostal loculi are narrow 

 and are crossed by small synapticulse separated by radially elongated per- 

 forations ; in the type the perforations in the intercostal loculi extending 

 to the center number eighteen; the intercostal synapticulaa and perfor- 

 ations are roughly arranged in concentric rows. 



The septa are thin and form five complete cycles arranged in six groups, 

 one group in each of the interspaces between the primary septa. Total 

 number of septa ninety-six. The secondaries extend to the columella ; the 

 tertiaries fuse against the secondaries near the columella; the two 

 outer quaternaries of the group fuse against the tertiaries nearer the 

 center than do the two inner ones ; the two outer quinaries of each of the 

 subgroups formed about the tertiaries fuse against the quaternaries nearer 

 the center than do the two inner ones. The primary septa are a little 

 higher than the members of the higher cycles, and the septa of the suc- 

 ceeding cycles appear to be each a little lower than those of the preceding 

 cycles. The edges of the septa are finely and distinctly denticulate, the 

 number of denticulations being eight or nine to 1 mm. ; the inner edges of 

 the primaries and secondaries are bifid, each presenting a trough-like 

 depression with serrated margins descending to the top of the columella ; 

 sides of septa with striae, tubercles, and rows of synapticulaa radiating fan- 

 like from near the base of the columella. Each septum is joined to the wall 

 (base) by synapticulae which connect with the intercostal synapticulae. 

 These are separated by perforations which connect with the intercostal 

 perforations. 



Columella elliptical in cross-section, spongy, trabecular, some of the 

 trabeculae terminating above in more or less scattered, irregularly dis- 



