84 EOCENE AND LOWER OLIGOCENE CORAL FAUNAS. 



i. e., on each side of the costa or septum standing next the one in the vertical 

 plane of the shorter diameter of the calice. 



All the septa in this large specimen seem to reach the columella, but 

 the calice is not perfect. The tliickening near the inner ends of the septa 

 has progressed still further, so there appears to be a lamina on each side of 

 the columella and joined to it by prolongations of the septa through the 

 lamina. The columella itself presents no peculiar characters. 



In both the young and old specimens, in the intercostal furrows are 

 pits, arranged in double rows, and they apparently perforate the wall. 



The details of the septal structure as interpreted from a study of the 

 flat surface of a septum are as follows : 



The septal margin, generally speaking, would be described as entire, 

 but it shows delicate crenations, the crenations corresponding to the emer- 

 gence at the surface of rows of granules. The septa are solid, made up of 

 completely fused ascending trabecuLn?. There is a line of divergence at 

 the interior edge of the wall. Interior to this line the trabeculse pass 

 upward, inclining slightly inward ; exterior to it they bend outward at a 

 considerable angle. The arrangement of the granules, the delicate, faint 

 striations around the septal margins, and the direction of the marginal 

 crenations were used to determine the trabecular constitution. 



It should also be noted that the septa seem to join pali, which stand 

 between the septa proper and the columella. In the longitudinal section 

 are four vertical rows of pores. The two external rows indicate the demar- 

 cation between septa and pali; of tlie other two rows, one is on each side 

 of the columella and indicates the lines of junction by cross projections 

 between it and the pali. (See PI. V, fig. 23.') 



Specimens. — United Statcs National I\Iuseuni; Philadclpliia Academy of 

 Natural Sciences, Lea's type. 



There has been much misunderstanding concei-ning this little species, 

 probably because it is so rare. M. de Gregorio seems to have had no speci- 

 men of it. The systematic position given to the form by Milne-Edwards 

 and Haime is undoubtedly the correct one. M. de Gregorio confused it 



' Some notes on the soft parts of the recent Splienotrovliiis ruhescenn are given by Fowler in tbe 

 Quart. Jour. Microsc. Sci. (N. S.), Vol. XX VIII, No. Ill, Feb., 1888, pp. 421-424. He states that the soft 

 tissues are outside the tbeca, there is no peripheral lamellie of the mesenteries, and the costa; corre- 

 spond to eutoca'lic septa. 



