﻿part 4] PHILLIPSASTRuEA HENNA flf, AND OH I ON ASTRAL A, 291 



The general surface of the corallum (as will be noticed in the 

 text-figure) rises towards the thecse, so as to form mound-like 

 borders to the calicular depressions, suggesting the idea of minute 



Fig. 3. — Distal surface of the type-specimen of 

 Aulina rotiformis, sp, nov. x 2 diameters. 



A. H. Harrow photo. 



[Fell Top Limestone, Harlow Hill (Northumberland). One half is in the 

 British Museum (Natural History), E. 17497, and the other half in the 

 Sedg-wick Museum, Cambridge.] 



craters. Within the calice the tubular wall terminates as an 

 elevated ring, forming a hollow axis against which the major 

 septa abut like the spokes of a wheel. 



Internal Characters. (PL XXII, figs. 6-11, & text-fig. 4.) 



The most distinctive feature is the tube traversing the tabular 

 tissue. Within this tube the tabulae are horizontally disposed, 

 and are remarkably flat ; externally to it, they take the form of 

 cones perforated by this axial tube. The dissepiments are very 

 small and regularly formed. 



All the septa dilate at the theca, and there the minor series 

 abruptly terminate. In these respects Aulina is similar to 

 Phillipsastrcea. The major septa, in an attenuated form, advance 

 towards the tube, to which their axial edges appear to be fused. 

 Actually, the septa dilate along their axial edges in such a way 

 as to present in cross-section the letter T, and form the tube 

 by the mutual fusion of these peculiar dilations into a perfect 

 wall. Confluence of the septa is well developed. 



Transverse section. — In this section the septa display the 



