46 BRITISH FOSSIL CORALS 



IX. Description of the Species. 

 SEcno^—JPOBOSJ. 

 Family— ASTR^ID^. J 



Division — LiTHOPHYLLACEiE SIMPLICES. 



Genus — Montlivaltia. 

 1. Montlivaltia Ruperti, Duncan. PI. XII, figs. 3, 4, 5 ; PI. XV, fig. 15. 



The corallum is turbinate ; it is truncated at the base, and is widest at the cahce. 



The epitheca is strong, and is marked transversely with ridges, prominent lines, and 

 constrictions ; the longitudinal markings are faint, but there is a tendency to split in 

 their direction. 



The caUce is moderately deep, and is circular in outline. 



The septa are crowded, unequal, long, and irregular ; the longest are thick internally, 

 and reach so far inwards as to give the appearance of a false columella ; all are slightly 

 spined. 



There are five cycles of septa, in six systems, and those of the highest orders are small, 

 whilst the primary and secondary are equal and very long. 



The wall is thick, and the epitheca does not project upwards as a ridge around the 

 circular margin. The endotheca is abundant. 



The costae are small, and are rarely visible beneath the epitheca. 



Height of the corallum /jjths inch. 



Breadth of the calice ^^ths inch. 



Locality. Down Hatherly. 



In the Collection of R. Tomes, Esq. 



Division — AsTR^EACEiE. 

 Genus — Isastr^ea. 

 1. Isastr^a Tomesii, Duncan. PI. XV, fig. 20. 



The corallum is massive, large, and irregular in shape. The upper surface is sub- 

 gibbous. 



The calices arc irregular in size, are separated by very thin walls, and are rather deep 

 and polygonal, quadi-angular, or more or less circular. 



