78 EOCENE AND LOWEE OLIGOCENE CORAL FAUNAS. 



M. de Gregorio lias characterized this species very well. The costse in 

 this species are very different from those of the two preceding. Through- 

 out most of theii- length the costaj of P. stokesi and P. goklfussi are made up 

 of a double or triple row of granules; but those of P. daibornensis, except 

 next the edges where they are thick and confused, show scarcely any gran- 

 ulations, and the granules are usually in a single row. The cost^, except 

 near the edges, resemble very closely those of Sphenoirochus. 



The columella in this species is identical in its general characters with 

 those of the two preceding. In a longitudinal section it is seen that addi- 

 tions are made to it by paliform lobes, which arise from the septa and are 

 slightly inclined inward. Later these pseudopali are united to the septa by 

 cross connections between them, leaving the line of fusion indicated by a 

 row of holes. Seen from above, the columella has a papillate surface. 



Mm. 



Greater diameter of calice 3. 6 



Lesser diameter of calice 2 



Height of corallum 5 



Locality. — (Jlaibome, Alabama. 



Geologic occurrence. ClaiborUe Sauds. 



A grain of sand is frequently included in the base of a specimen. 



Geuus DISCOTROCHUS Milne-Edwards and Haime. 



1848. Dincotrochus Milne-Edwards and Haime. Annales sci. nat., 3d ser.. Vol. IX, 



p. 251. 

 1857. DiscotrocUm Milue-Edwards and Haime. Hist. Nat. des Corall., Vol. II, p. 76. 



1883. Biscotrochus Zittel. Traite de Pal., Vol. I, p. 275. 



1884. Discotrochus P.M. Duncan. Revision of the Genera of Madreporaria: Jour.Linn- 



Soc, London, Vol. XVIII, p. 30. 



" Corallum simple, discoid, free, without any trace of the place of 

 fixation. Calice somewhat flat, columella fasciculate and papillate on its 

 surface. Septa slightly exsert. The Vvfall horizontal, naked, and presenting 

 simple costa?." ^ 



The wall is, at least in part, a pseudotheca. The columella is com- 

 posed of several erect rods (or erect trabecular) that fuse from place to place 

 one to another or to the septa l)y crossbars. The septal trabeculse next the 

 columella are erect, and sometimes, by becoming separate from the main 



'Hist. Nat. des Corall., loc. cit. 



