Geological Society. 'I'M 



The corallum in this genus, as also in PhiUipaaHrcpa and in 

 Orionastrcea, represents a stage in colonial development in which 

 the epitheca of the individual coi-allites has entirely disappeared, 

 and these are consequently united by their dissepimental tissue — 

 a type of colony to which the term ' Astrajiform ' may be applied. 



Diagnoses. 



Aulina rotiformis. — The corallum is massive, and the corallites 

 are united by their extrathecal tissue ; all the septa dilate at the 

 theca, and those of the major cycle again dilate at their axial edges, 

 in such a manner as to fuse together, and so build a cylindrical Avail 

 or tube within the theca. The structure of the form is in most 

 respects similar to that of Phillipsasfrcea, but it appears to carry 

 forward the septal characters peculiar to tlmt genus to a fm'ther 

 stage of development. 



PhiUipansfrcpn. — The corallum is composite and massive; the 

 corallites are united by their dissepiments, or are only separated by 

 a thin epitheca ; in the former case, the septa are often confluent. 

 Major and minor septa dilate at the theca ; the latter terminate 

 there, and the major septa attenuate and advance into the intra- 

 thecal region, and there often dilate again at the axial edge. The 

 central part of the corallite is occupied solely by tabulse. 



OrionastrcEa. — The characters of this genus are essentially those 

 of Lithostrotion, but of a modified form. The corallum is compo- 

 site and massive, and the corallites are either defined by a thin 

 epitheca, or, in the more typical instances, by no epitheca at all ; in 

 this latter case the corallites are united by their dissepiments and 

 the septa are confluent. 



The distii^uishing characters of the three species recognized and 

 described are as follows : — 



(1) 0. enaifer (Edwards & Haime). Septa not confluent. Columella present. 



(2) 0. phUlipsi (McCoy) Septa confluent. Columella present. 



(3) 0. plnceiitn (McCoy) Septa confluent. Columella absent. 



November 22nd, 1910. — Dr. Alfred Ilarker, F.ll.S., President, 

 in the Chair. 



The following communication was read: — 



' Characeae fi'om the Lower Headon Beds.' By Clement Reid, 

 F.R.S., F.L.S., F.G.S., and James Groves, F.L.S. 



'I'he investigations here recorded have been made at Hordle ClifFs 

 (Hampshire), where the strata, below the sujji'rticial gravel, belong 



