82 EOCENE AND LOWER OLIGOCENE CORAL FAUNAS. 



soon developed on the middle of each lateral face, making eight. In the 

 next succeeding stage eight more costpe are introduced, bringing the number 

 up to 16. The next stage possesses 24 septa. Each costa standing next 

 the median costa of each lateral face has another costa introdiiced on each 

 side of it — four costa on each face, eight in all. These eight, added to the 

 16 previously developed, make 24. 



The next young specimens to be described being attached do not 

 permit the costal development to be followed so closely. 



The youngest specimen, or at least the smallest, is 1.5 mm. high, and 

 is attached to a sand grain. It shows IG costa3 extending to the object of 

 sup]iort. Soon after this a costa is introduced on either side of each one of 

 the four costse standing next the median costse of the lateral faces. So that 

 the young coral, only 1.5 mm. high, has already (so called) three cycles of 

 septa and as many costal. Twelve septa (every other one) reach the 

 columella. 



The specimen next in size to the. one last described is about 2.75 mm. 

 high. It has the same number of costse and septa. The costas are not 

 very*all, are somewhat thin, and have a rounded edge. On the ilat side 

 are striations that run in a horizontal direction. At this stage no costa 

 shows a tendency to become especially thicker than the others. The col- 

 umella is as represented in the figure of the calice of Lea's type, PI. V, 

 fig. 20. Most of the twelve large septa show a thickening on the inner 

 margin, just before j(iining the columella, and at the thickening a small 

 tooth can be distinguished. 



The next stage is represented by a specimen of the following dimensions: 



Mm. 



Greater diameter of calice 2.3 



Lesser diameter of calice 1. 75 



Height of coralliim 4. 25 



The calice of this specimen is represented by PI. V, figs. 21 and 21a. 



The costaj are rather low, flat or rounded in profile, and jiossess 

 minute granulations. At this stage ten additional costa? have been added, 

 one costa on each side of each of the four costaj on the faces of the coral- 

 lum, next the sejjta at the ends of the shorter axis of the calice; and two 

 more costaj have arisen, one on each side of one costa of the last cycle 

 standing next the one on the middle of the face. The costse standing at 



