Vol. ()-.'' THE CARBONIFEROUS SUCCESSION IN GOWER. 



555 



Evolution of Z. oystermouthensis. — Among the Z l forms, 

 which may all be attributed to Z. delanouei Ed. & H., is one which 

 agrees very closely with the young stage of Z. oystermouthensis 



Y\g. 10. — Zaphrentis oystermouthensis, sp. nov. : contoured plan of 

 floor of calyx, magnified 2 diameters, and two sections on the 

 same scale across the calyx. (Specimen figured in PI. XL, 

 fig- 1 a.) 



depicted in tig. 1 b (PL XL) ; if this form represents the ancestral 

 member of the gens of Z. oystermouthensis, variation has merely 

 increased the size and emphasized the irregularity of the septa in 

 direction and thickness. 



Caninia. 



Caninia aff. cornucopia Mich., mut. D 2 _ 3 . (PI. XL, figs. 3 a-Sc.) 



I have already described the characters of this mutation under the 

 generic title of Amplexi-Za/plirentis, in the ' Eush Paper ' p. 315 & 

 pi. xxix, fig. 7; and also in a note kindly inserted by Mr. Carruthers 

 in his ' Revision of Carb. Corals ' Geol. Mag. 1908, p. 169. 



Consequently, it is only necessary here to point out the differences 

 between the Upper Avonian form of the >South-"\Vestera Province 

 and the Lower Avonian species of the same region (Z 2 -y), an 

 example of which is figured in PI. XL, fig. 4. These differences 

 are appreciable only in the adult, and by comparison of the 

 average form at the two levels. 



Q. J. G. S. No. 268. 2 a 



