FROM THE ZONE OF AMMONITES ANGULATUS. 



19 



2. AsTROccENiA PLANA, Duucan. PI. Y, fig. 1. 

 The corallum is large, flat, and short. 



The calices are small, very regular in their linear arrangement, polygonal, and nearly 

 equal : they are rather deep and rather distant. 



The septa appear to be from eight to ten in number, and reach the columella. 

 The costae are very indistinct. 

 The columella is large. 



The coenenchyraa is well developed, and becomes divided into rounded eminences 

 betvi^een the calices ; and where four of these are together, the intervening coenenchyraa is 

 decidedly peaked. 



Three of the largest cahces, with the intervening ccenenchyma, cover a length of 

 fliths inch. 



Locality. The Sutton Stone. In the Museum of Practical Geology, London. 



3. AsTROccENiA iNsiGNis, Duncan. Plate IX, figs. 1 and 2. 



The corallum is large ; it is flat on the upper surface, and is short. 



The calices are somewhat regular in their Hnear arrangement ; they are unequal, aiul 

 are irregular as regards their outline and distance. They are shallow, and are large in 

 comparison with those of most of the species of the genus. 



The septa are large, and nearly equal in size at the calicular margin, but all do 

 not reach the columella. Generally five primary septa extend to the columella, and there 

 are three which only reach a little way into the calicular fossae between the longer pri- 

 mary. The central of these smaller septa is often longer than those on each side of it. 

 The septal number is irregular, but twenty is the usual number. In some calices the 

 shorter septa are decidedly smaller than the others. 



The costse are large, broad, straight, nearly equal, club-shaped, close, and are oblique 

 in some, but flat in other calices. They extend over the ccenenchyma when it exists, do 

 not coalesce with those of other calices, and are often separated by a ridge. Neither 

 septa nor costae appear to be spined or dentate, but a very slight unevenness of the margin 

 may be noticed in well-preserved specimens. 



The columella is small, sharp, and prominent. 



The size of the calices varies, and in large specimens, where there is some ccenenchyma, 

 three calices and their ccenenchyma occupy rather more than ^ths inch. The smallest 

 calices, with a small quantity of ccenenchyma, do not occupy one half of that space. 



Locality. — Brocastle. In the Collection of Charles Moore, Esq., F.G.S., Bath. 



