PROM THE ZONE OF AMMONITES PLANORBIS. 65 



XXII. Corals from the Zone of Ammonites planorbis.^ 

 Division — Astr^acejE. 

 Genus — Isastr^a. 

 1. IsASTRiEA latim^androidea, Duncan. PI. XV, figs. 18, 19. 



The corallum is massive, and lias an angular and rather gibbous upper surface. 



The corallites are long, and their united walls are thick. 



The calices are very irregular in shape, and although some are small and polygonal, 

 others are more like the serial calices of the genus Latimeeandra. The calices are deep, 

 and gemmation takes place quite on the margin. 



The septa are numerous, very unequal, and there is a very small septum betvpeen the 

 larger. The larger septa are very dentate, and the tooth near the axial space is very 

 distinct, especially in the long calices. The larger septa are not very unequal, do not 

 project much into the calice, and the axial space is left very free^ but is closed by 

 endotheca. The existence of the small rudimentary septa makes the septal number very 

 irregular, and the long serial calices contain very variable numbers of septa. 



The endotheca is strongly developed, is vesicular, and closes in the corallites. 



Diameter of ordinary calices ^ths inch to ^ths inch. 



Diameter of serial calices i^ths inch. Length of serial calices j^gths — ^ths inch. 



Locality. " No. 3^' bed in the Street section. 



In the Collection of Dr. Wright, F.G.S. 



This is a most remarkable species, and the existence of serial calices with an abundant 

 marginal gemmation is very suggestive. It renders the genus Latimeeandra of rather 

 doubtful value. The new species is readily distinguished by the calices and the dentate 



It is erroneously named Isastrcea Murchisoni by some collectors. 

 The locality whence the specimen was derived is the same which yielded Septastraa 

 Haimei, Wright, sp. 



Genus — Thecosmilia. 



Some small stunted Corals have been found in the " Guinea bed" at Binton, in Worces- 

 tershire. Only one specimen is fairly preserved, and its calice is so like that of Thecosmilia 

 Terquetni, Duncan, from Brocastle, that it must be referred to that species. 



1 The specimens from the Zone of Ammonites planorhis were not forwarded for description until after 

 the first part of this Monograph was finished. 



