314 



DR. A. VATTGrHAJST ON THE EAUNAL SUCCESSION [May I906, 



Zaphrentis cf. Phtllipsi, Edwards & Haime. 



See Vaughan, Quart. Journ. Geol. Soc. vol. lxi (1905) p. 269 & pi. xxii, 

 figs. 2-2 e. 



The points of resemblance with Zaplirentis aff. PJiillipsi, which 

 characterizes Z in the South-Western Province, are : — 



(1) External form and dimensions. 



(2) As seen in a horizontal section : — 



The spacing and number of the primary septa. 



The rudimentary development of secondary septa. 



The strong fossula, occupied by a long fossular septum. 



The antifossular group of septa, bounded below by the elongation 

 and union of the two extreme septa, and marked off from the 

 fossular group by rudimentary lateral septal breaks. 



The differences, are, however, strongly marked in the following 

 characters of the Rush Zaplirentis : — 



The septa composing the fossular groups are directed towards the centre, 

 and not towards the walls of the fossula ; the fossula is, consequently, bounded 

 by a single septum on each side, and is narrowly rectangular in section. 



The middle of a horizontal section exhibits concurrent septa, whereas, in the 

 Zaplirentis, of the South-Western Province, the inner ends of the septa are 

 merged into a dense central disc, formed by the intersection of the plane of 

 section with one of the tabulae. 



In these differences Zaplirentis cf. PJiillipsi makes an approach 

 towards Z. aff. EnnisJcilleni (see p. 315), hut the latter exhibits the 

 following distinctive characters : — 



(1) The tendency of the antifossular septa to fall short of the centre ; 



(2) The fossula lies on the concave side of the coral, whereas, in Z. cf. 



Pkillipsi, it is, apparently, always on the convex side ; 



(3) The absence of a long fossular septum ; and 



(4) The larger dimensions. 



Two rather striking peculiarities are 

 commonly exhibited by variants of the Hush 

 Zaplirentis : — 



(1) A marked development of an antifossular 

 break, which strongly resembles the fossular 

 break. 



This character is also exhibited, though less 

 commonly, in the Zaplirentis of the South-Western 

 Province (see pi. xxii, fig. 2 c, op. supra cit.). 



(2) The frequent development of an axial tube 

 caused by the wrapping-round of the septa. 



In this character there is a distinct approximation 

 towards Z. BowerbanJci, Edwards & Haime, but the 

 Push coral is always separated by its short conical 

 form, and by the fact that the antifossular septum 

 does not extend into the axial tube (see fig. 13). 



More information is required as to the 

 tabulae of the Rush Zaplirentis, but this can 

 only be obtained from good vertical sections. 

 The Zaphrentis-Be&s only. 



Fig. 13. — Zaphrentis 

 r/.Phillipsi,^.^., 

 variant towards 7i. 

 Bowerbanki, E.SfH., 

 showing the cross- 

 section of the axial 

 tube. From the Za- 

 phrentis - Beds of 

 Bush. 



Ran ere.- 



