﻿282 DK. A. VAUGHAN ON THE PALJEONTOLOGICAL [May I905, 



Examples from the Bristol Area. 

 Koninckophyllum. 



KONINCKOPHXLLUM 6. (PI. XXIII, fig. 4.) 



The form is conical and elongate. 



The calyx is deep, and has a helmet-shaped boss projecting from 

 its floor. A. thick mesial plate forms the crest of the boss, and 

 continues, as a lamella, towards the fossula. The sides of the boss 

 are smooth, except for one or two inconspicuous lamellse. 



The horizontal section well exhibits all the characters of the 

 genus, already explained. 



Axophyllum, 



AXOPHYLLUM 6. (PI. XXIV, fig. 4.) 



The form is short, broad, and turbinate. 



The calyx is deep, and has a prominent, laterally-compressed, 

 solid style projecting from its floor. 



The horizontal section exhibits the highly-specialized characters 

 of the genus, as already explained. 



Microscopic examination reveals the essentially-complex nature of 

 the solid columella, as above stated. 



Section II. (The Dibunophyllum- Group.) 



This section comprises the most typical members of the family, 

 in which the central area is strongly developed and exhibits a 

 thickened mesial plate and well-marked lamellae. 



Here I include Dibunophyllum, Clisiophyllum, Aspidophyllum, 

 and, tentatively only, Carcinophyllum. 



Thomson points out the following distinctions between the three 

 first-mentioned genera: — 



(a) In horizontal sections. 



In Dibunophyllum, Nich. & Thorns., the mesial plate stretches completely 



across the central area. 

 In Clisiophyllum (Dana), Thomson, the mesial plate crosses the centre, but 



does not extend to the circumference of the central area on either side. 

 In Aspidophyllum, Thomson, the mesial plate is only conspicuous, between 



the centre and the circumference of the central area, on the fossular side. 



(b) These distinctions correspond to the following differences in the 



nature of the calicinal boss : — 

 In Dibunophyllum, the boss is elongate and dome-shaped, with a long crest- 

 In Clisiophyllum, the boss is conical, with a very short crest. 

 In Aspidophyllum, the boss is shaped and crested like a fireman's helmet. 



Eor the present, I shall include Aspidophyllum as a subgenus of 

 Dibunophyllum, for two reasons :- — 



(1) There appears to me to be no essential difference between the horizontal 

 sections of Aspidophyllum, as shown in pi. xiii, figs. 7 & 8, Proc. Phil. Soc. 



