FROM THE ZONE OF AMMONITES ANGULATUS. 7 



Section— ^P OB OS A. 



Family— ASTR^IDtE. 



Division — Lithophyllace^ simplices. 



Genus — Montlivaltia. 



There are seven species of the genus Montlivaltia in the Sutton Stone and the deposits 

 at Brocastle, and six of theiu are new forms, the seventh having ah-eady been described 

 by MM. Terqnem et Piette.^ Three of the species belong to the section of the genus 

 which is characterised by forms having their bases and calices of equal width, and three 

 others have a more or less turbinate shape, whilst one species is pedunculated. The 

 discoid Montlivaltits appear to be absent, although they are largely represented in the 

 equivalent beds in the east of England and in the north of Ireland. 



I. Montlivaltia Walli^, Duncan. PI. VIII, figs. 5, 6, 7. 



The corallum is cylindro conical in shape, the base is small, and the calice large, open, 

 and. shallow. 



The calice is surrounded with a well-marked margin, which is double in some places, 

 and the smallest or rudimentary septa, which are barely visible in the true calice, are 

 distinct on the outer rim. 



The septa are very unequal, but narrow and lamellar, and rather plain, but dentate 

 internally. They are not exsert as regards the calicular margin, but curve upwards and 

 then inwards, terminating by a process marked with at least two teeth. 



The fourth cycle of septa is incomplete, and the fourth and fifth orders are rudi- 

 mentary when they exist ; so that the septal number is irregular. The rudimentary septa 

 alternate with the larger. There are about thirty well-developed septa of unequal lengths, 

 and between these are the rudimentary septa. 



Height of the corallum, ^ths inch. Breadth of the calice, ~ths inch. 



Locality. Brocastle,' In the Collection of Chas. Moore, Esq., F.G.S., Bath. 



The wide and shallow calice, the low septal number, and the capacious interseptal 

 spaces characterise this species. 



' Terquera et Piette, ' Mem. de la Soc. Geol. de la France,' 2de serie, torn. 8, 1865. 



