22 PEOP. p. MAETIlSr DUlSrCAN's EEVISTON OP THE 



otliers whicli have endured from the Cretaceous age to the pre- 

 sent day, and some which flourished during tlie Eocene and still 

 exist. Some genera are dwellers in the deep sea. Any turbi- 

 nate-shaped species of the genus Trocliocyathus and any form of 

 the genus GeratotrocJius may be taken as the types of th.e two 

 great groups of the alliance, the one with and the other without 

 pali. 



Genus Teochoctathus, MM. Milne-Edwards Sf Jules Haiine, 

 Ann. des Sci. Nat. 3^ ser. t. ix. p. 300 (1848), amended. 



8jn. A^loci/athus, d' Orb.; Stephanoci/athus, ^eguenza,; Platy- 

 cyathus, E. de From. 



The corallum is simple, pedunculate or subpedicellate, or 

 merely shows the trace of a former adhesion. Tlie shape may be 

 elongate, turbinate, subturbinate, straight, curved, compressed 

 or not, or more or less discoid and flat. The calice is deep or 

 widely open. The septa are long and usually some are exsert. The 

 pali are in two crowns. The columella is formed of trabeculse, 

 is essential, and may or may not be papillary. The costse may 

 or may not be well developed, crested, spined, or simply projecting. 

 Epitheca variable. 



Distribution. — Fossil. Lias to Recent. Fossil forms world- 

 v^dde. — Recent. West Indies, South- Australian seas. 



The genus is a large one, and should include some subgenera. 

 Its species have been divided into the following groups by 

 Milne-Edwards and Jules Haime : — Trocliocyatlii striati, with 

 the wall marked Avith but slightly projecting costee ; and Troclio- 

 cyatlii armigeri, with the costse well developed, crested, spined, 

 or warty. In both of these divisions the shape of the coral is 

 very variable. 



Subgenus Teopidoctathus, Ed. Sf FL. 



The corallum is compressed ; the wall is naked, and has a basal 

 expansion. Pali before all the cycles except the last, and they 

 form more or less marked chevrons. 



Subgenus Thecocyathtjs, Fd. Sf S. 



The epitheca surrounds the wall and reaches the calicula 

 margin. Corallum with a fixed and broad base, or not fixed. 



