INTRODUCTION. 



3. Genus Acanthocyathus. 



Milne Edw. and J. Haime, loc. cit., p. 292, 1848. 



Corallum simple, free, subturbinate, slightly compressed, and subpedicellate. 

 Calice more or less oval. Columella and pali as in Cyathina. Septa broad, exsert, and 

 forming five cycla; systems unequally developed, so as to form sixteen groups. Costa 

 partly armed with crests or spines. 



Typ. sp., Acanthocyathus Grayi, Milne Edw. and J. Haime, loc. cit., tab. ix, fig. 2. 



4. Genus Bathycyathus. 



Milne Edw. and J. Haime, loc. cit., p. 294, 1848. 



Corallum simple, adherent by a broad basis, tall, subturbinate, and slightly com- 

 pressed. Calice subelliptical, with a broad and very deep fossula. Columella small and 

 crispate. Pali narrow, feeble, entire, and closely united to the septa. Septa exsert, thin, 

 closely set, and forming apparently twelve equally developed systems ; five cycla, the last of 

 which is more developed than the penultimate one, the septa of which are closely approxi- 

 mated towards the wall, or even cemented to those of the primary, secondary, and ternary 

 cycla. Costa very narrow, straight, unarmed, delicately granulated, and distinct down to 

 the basis of the corallum. 



Typ. sp., Bathycyathus chilensis, Milne Edw. and J. Haime, loc. cit., tab. ix, fig. 5. 



5. Genus Brachycyathus. 



Milne Edw. and J. Haime, loc. cit., p. 295, 1848. 



Corallum simple, extremely short, widening very rapidly, and becoming free in the 

 adult state. Calice circular, and very slightly excavated. Columella very thick, fasciculate, 

 and terminated by circular papillae. Pali very broad, entire. Septa exsert, narrow, and 

 forming four cycla ; the systems equally developed, and apparently twelve in number. 

 Costa unarmed. 



Typ. sp., Brachycyathus Orbignyanus, Milne Edw. and J. Haime, loc. cit., tab. ix, fig. 6. 



6. Genus Discocyathus. 



Milne Edw. and J. Haime, loc. cit., p. 296, 1848. 



Corallum simple, free, and discoidal. Calice circular and slightly convex. Columella 

 formed by a single vertical lamina; its apex smooth and undivided. Pali free and 

 corresponding to the septa of the antepenultimate cyclum. Septa very exsert, broad, and 

 striated laterally near their apex. Wall horizontal, and covered with an epitheca presenting 

 some concentric striae. 



Typ. sp., Biscocyathus Eudesii, Milne Edw. and J. Haime, loc. cit., tab. ix, fig. 7. 



