20 BRITISH FOSSIL CORALS 



LocaUfy. Upper Greensand of Cambridgeshire. In the Collection of Jame^ 

 Carter, Esq. 



4. Smilotrochus angulatus, Duncan. PI. VII, figs. 7, 8. 



The corallum is conical, hexagonal, and slightly curved at its very fine inferior ex- 

 tremity. It is broad superiorly, has six prominent angles, and is slightly compressed. 



The septa are fine, unequal, and each plane between the angles has a system of four 

 cycles. 



The columellary space is large. 



Height, 2ths to 1 inch. Breadth, I inch. 



Locality. Upper Greensand, Cambridge. In the Collection of James Carter, Esq. 



Genus — Onchotrochus. 

 Onchotrochtjs Carteri, Duncan. PI. VIII, figs. 1 — 14. 



In the young corallum there is a flat and rounded expansion at the base, by which it 

 was attached to foreign substances, but this is lost as growth proceeds. 



The corallum is either straight or slightly curved, is tall, very slender, cylindro- 

 conical, clavate, and enlarged here and there. 



The worn specimens are more or less angular in transverse outline. 



The costse are angular projections, which extend from base to calice ; they are sub- 

 equal, wide apart, and are connected and covered with a fine, striate, pellicular epitheca, 

 which readily disappears. 



The growth-markings are very common. 



The calice is circular and shallow. 



The septa are stout at the walls and Avedge-shaped ; they are rounded superiorly, and 

 do not extend far inwards. There are twelve septa, and they are subequal. The septa 

 in sections often appear to be equal, and their inner ends are joined, and the axial space 

 is filled up by a deposit of coral structure ; but the reverse is the case occasionally, and 

 the irregularity of the septa may often be well seen. The septa are continuous with the 

 costse. 



Height, ird — |rds — 1 inch. Diameter of costae, jsth — i^th inch. 



Locality. Cambridge Greensand. In the Collections of James Carter and Rev. T. 

 Wiltshire, F.G.S. 



