326 PROFESSOE P. M. DUNCAN ON THE 



9. as no. 8. The primai-y and secondary septa are exsert. 



Surface of the wall sharply and finely granular. Costal striae near new calices. 



10. as no. 8. All the septa are exsert, and the costal striae are strong. 



11. as no. 10. The costae are cristiform near the calices. 



12. Columella well developed. 



The septa are in three cycles ; and sometimes one of a higher order is present. 

 Striae long and granular, often not continuous. 

 Granules long. 



13. Surface like shagreen, otherwise as no. 12. 



It may be gleaned from this table that there are four groups: — 1, with a plain wall- 

 surface ; 2, with a striated wall-surface ; 3, with exsert septa ; 4, with exsert septa and 

 long striations and sharp granules. 



Consequently the following diagnosis will include all the forn^s of AmpMJielia, 



Genus Amphihelia. 

 Syn. Diphohelia. 



The corallum is bush-shaped ; and the gemmation is alternate, marginal, and often 

 double. The wall increases in thickness at the lower part of the corallum, and often 

 includes the formerly free corallites. The corallites often coalesce. The columella 

 exists. The septa are in six systems. There are not many cycles of them. The 

 ornamentation of the wall may be none, or the costal striae may exist. 



The corallites do not fill up from below. There is no dissepimental tissue. 



Amphihelia oculata, Linnaeus, sp. (Plate XLV. figs. 1-3.) 



Branches irregular and coalescent. Calices distant and circular in outline, very 

 prominent on the younger branches, and immersed in the wall-tissue lower down in 

 the corallum. Columella moderately developed. Septa in six systems; and either 

 three cycles are developed, or only two, the third being rudimentary. Septa unequal 

 in the first case, and equal in the second. Wall-surface plain, and striated near the 

 new calices. 



Variety a, with some septa slightly dentate. 

 Variety |3, with the surface of the wall granular. 

 Variety y, with exsert septa. 



Amphihelia eamea, Miiller, sp. (Plate XLV. figs. 4-6, Plate XLVI. figs. 1-19, and 

 Plate XLIV. figs. 1-3.) 



Syn. Amphihelia miocanica, Seguenza, 



atlantica, nobis. 



ornata, nobis. 



Diplohelia profunda, Pourtales. 



