DESCRIPTIONS OF SPECIES. 57 



lower portion, owiug- to internal calcareous deposit. Epitlieca well devel- 

 oped, extending to the upper edge of the corallum wall. Septa slightly 

 exsert, margins entire; inner free portion undulated, sides granulate. In 

 the adult there are 16 principal septa. Septal arrangement four complete 

 cycles, members of the fifth cycle appearing near the ends of the longer 

 transverse axis. In the specimen illustrated in PI. Ill, fig. la, there are 72 

 septa, which are divided as follows: 



First cycle 6 



Second cycle 



Third cycle 12 



Fourth cycle -i 



Fifth cycle 24 



Total "2 



Of the 16 principal septa, 12 belong to the first and second cycles, and 

 4 to the third cycle. The septa of the third cycle near the termini of 

 the longer transverse axis join tlie columella. In moderately young speci- 

 mens, such as illustrated in PI. Ill, fig. 3, there are three complete cycles, and 

 members of the fourth cycle are appearing near the ends of the longer 

 transverse axis of the calice. The septa of the third cycle (PI. Ill, fig. 3) 

 have just reached the columella as thin lamella?. In PI. Ill, fig. 4, these 

 youngest principal septa have become much thickened. The study of young 

 forms of this species clearly shows that the explanation given by Semper^ 

 for the number of principal septa in Flabellum, intermediate between 12 

 and 24, and further amplified by von Marenzeller,^ holds for this species, as 

 well as for the ones they studied. 



The columella is typical for the genus, i. e., is formed by the fusion of 

 septal trabecular. Calice not very' deep. 



'Zeitschr. fiir wis*. Zooloft., Vol. XXIT, 1872, pp. 243 et seq. 

 2Z.)ol. .Jahrb. 1«87, Vol. Ill, Pt. I, pp. 25-50. 



