AND GLYPHASTRJ^A, DUNCAN (1887). 219 



abnormally large forms reach to 8*5 millira. in width, but show no 

 signs of fission. 



This species is distinguished from Septastrma sexradiata, Lonsdale, 

 sp., by the non-development in the calicos of the third cycle of septa. 



Distribution. Miocene Tertiary, Southampton, Virginia, and Mary- 

 land, United States of America. The type specimen is in the Brit. 

 Museum Nat. Hist., South Kensington. 



Septastr-^la sexradiata, Lonsdale, sp. (PI. IX. figs. 6, 16.) 



1845. Columnaria (?) sexradiata, Lonsdale, Quart. Journ. Geol. 

 Soc. vol. i. p. 497, figs, a, h. 



1^)45. Columnaria i^^) sexradiata, Lyell, ibid. p. 416. 



1857. Astrangia'i bella, E. & H. Hist. nat. des Corall. vol. ii. 

 p. 615. 



1861. Astrangia ? bella, de Eromentel, Introduction &c. p. 237. 



1864. Septastrcea (?) sexradiata. Meek, Check-list Invertebrate 

 Possils N. American Miocene, p. 1. 



1887. Glyphastrcea sexradiata, Duncan, Quart. Journ. Geol. Soc. 

 vol. xliii. p. 30. 



Corallum forming large masses of a similar character to those of 



5. Forbesi, the lower portion of the corallites varying, in transverse 

 section, from approximately circular to polygonal, and their walls 

 are thin. In the lower portion the corallites have usually 12 septa. 

 but frequently only six are present and reach the centre of the 

 corallite. The septal surfaces in the interior are smooth. The 

 inner septal margins occasionally intertwisted, so as to form a pseudo- 

 columella, as in S. Forbesi ; but there are no indications of a true 

 columella. The nature of the septa and of the theca precisely as 

 in >S'. Forbesi, and the upper portion of the corallites similarly 

 filled with stereoplasm. The calices shallow, with their central 

 portions from 1 to 2 millim. below the margins. The upper surface 

 of the corallite-walls and the septal edges in the calices covered with 

 minute blunted tubercles. The floor of the calices completely closed 

 with a film of stereoplasm, save in a few immature calices, in which 

 the interlocular septal spaces are open. The septa in the calices are 

 slightly elevated blunted ridges ; they sometimes disappear before 

 reaching the centre, and the axial space, when perfect, is covered 

 with minute tubercles. 



In the calices 24 septa are clearly shown, of which 4, and sometimes 



6, are markedly prominent, and these generally reach to the centre ; 

 as a rule 12 septa extend nearly or quite to the axial area, and the 

 intermediate 12 septa of the third cycle reach about halfway and 

 then either bend and unite with the larger septa, or more frequently 

 remain free. Though the 12 septa of the third cycle are thus plainly 

 developed in the calices, they cannot be distinguished in the lower 

 portion of the corallites, where only the 12 septa of the first and 

 second cycles are present. 



The dissepiments are horizontal, and from 1*5 to 2-5 millim. apart. 



q2 



