144 EOCENE AND LOWER OLIGOCENE CORAL FAUNAS. 



pass vipward and then ontward from the columena space, forming cnr^'es 

 parallel to the septal margins (see PI. XVI, fig. 4). These little waves are 

 narrower near the columella, becoming wider near the corallite wall, 

 sometimes bifurcating. The transverse measurement near the columella is 

 slightly less than 0.11 mm.; near the wall al)out 0.22 nun. Besides these 

 minute undulations there are frequently strong transverse flutings, espe- 

 cially near the inner termini of the septa; to these the dissepiments are 

 usually attached. 



A section parallel to the flat surface of a septum possesses a double 

 structure (see PL XVI, figs. 5, 5a). First there are curves parallel to the 

 septal margin, along which are dark points; these curves are 0.05 to 

 0.10 mm. apart, the dark points about 0.02 mm. apart. Second, there are fine 

 lines normal to the curves first described, and passing between the dark 

 points. By comparing these data with the preceding, it will be seen that on 

 the same side of a septum the distance from the top of one undulation to 

 that of the next is about twice the distance between the series of dark points 

 (calcification centers). As the undulations on the septa alternate in position, 

 the distance between neighboring septa and between the series of calcifica- 

 tion centers coincides. 



The septa in a cross section of a corallite shows a median line rec- 

 ognizable from the surrounding calcareous deposit. This median line varies 

 irr appearance according to the condition of preservation of the material; 

 sometimes it is lighter in color, sometimes darker, than tlie more external 

 portions of the septum. In a considerable luimber of sections series of 

 small calcification centers were distinguishable. These were from apprt)xi- 

 mately 0.02 to 0.037 mm. apart, the distance corres])onding to the dark 

 points in the curves previousU' descril)ed. The fillers passing outward 

 from the median septal plane are, in the outer portion of the septum, in a 

 general way perpendicular, or almost so, to tliat jjlane. Near the inner 

 ends of the septa the fillers diverge inward from the median septal plane. 

 In a somewhat oblique section calcification centers were cut across, and 

 mea.sured approximately 0.064 nmi. to 0.09 mm. The calcareous fibers 

 diverge upward and outward. 



As the state of preservation of the material is not good, the above data 

 were obtained only after a long study of tlie sections, and are not given 

 with the degree of precision desirable. The following seems the only 

 possible interpretation of the septal structure. 



