100 



The costse are fine trenchant ridges; those of the first three 

 cycles radiate from the centre to the circumference, but those of 

 the lower cycles do not reach the centre. 



The septa are in six regular systems and five complete cycles; 

 they are extremely thin and are not in the least echinulate ; 

 those of the fourth cycle unite with each other over those of the 

 third cycle some distance from the columella, and those of the 

 fifth cycle curl in and unite with those of the fourth still further 

 back. The union of the quinaries with the quaternaries is discon- 

 tinuous, so as to give an appearance of synapticulae. 



Thin irregular, and ragged pali are present before all the septa 

 except those of the last cycle. 



Columella of good size, of a delicate reticular and encrusting 

 texture. 



From all other species of Deltocyathus this is distinguished by 

 its delicate, brittle, vitreous texture, and thin non-echinulate septa. 

 In form and texture. and in the synapticula-like union of the 

 quinary with the quaternary septa, it resembles Trochocyathus 

 rotulus mihi. 



The corallum of the largest specimen is 17 millim. in diameter. 



16. Odontocyathus sexradiis n. sp. 



The corallum is bowl-shaped, with the edges very deeply scal- 

 lopped between the enormously exsert primary septa, and is sup- 

 ported on six long, strong, solid, smooth, radiating legs, which 

 correspond in situation with the primary septa. 



The costas are but little more than ridges marked only on the 

 sides of the bowl, not on the base where there is a smooth 

 mammilary scar. 



The septa are in six systems and five cycles. with a sixth 

 cycle developed in some of the quarter-systems.» Those of the first 

 cycle are the largest and far the most exsert, and they carry up 

 with them those of' the inferior cycles lying immediately on either 

 side of them, which therefore are more exsert than all the other 



