308 DR. A. VATJGHAN ON THE EAFNAL SUCCESSION [May I906, 



Productus, but the spine-ornament is exactly that of Pr. punctaius. 

 This group is represented in the Cyathaxonia-Be&s by a common 

 form which appears to be identical with Pr. elegans. 



In the Upper Dibunophyllum-Zone of the South- Western Province, 

 a closely-similar, but larger, form is equally characteristic of the 

 uppermost Avonian. 



The specimen figured by Martin under Pr. punctatus, 1 as well as 

 Phillips's figure of Pr. fimbriatus, 2 must be described as examples 

 of Pr. punctato-fimbriatus, intermediate between Pr. fimbriatus and 

 Pr. elegans. 



A single specimen of a very peculiar fimbriate Productus was 

 found by Dr. Matley just above the Megastoma-Beds , 



The form and concentric banding are exactly those of Pr.fim- 

 briatus, but the spine-bases are few, scattered, and usually erect. 

 The relationship of such a form is very obscure, but probably it 

 represents a link between the fimbriate and the aculeate Producti. 

 The specimen is figured under the name Productus cf. fimbriatus, 

 PI. XXX, fig. 6. 



Peodttctus maegaeitacetjs, Phil. 



This Productus is highly characteristic of the Cyathaxonia-Be&s, 

 and it occurs at the same level, both in the South-Western Province 

 and in the Midland area. 



Peodtjctes coeeugatus, M'Coy. 



Specimens which appear to be identical with M'Coy's t}<pe a 

 occur in the Curkeen Limestone and in the C'yatha.vonia-Beas of 

 the Eush sequence. The same form occurs in the Upper Dibuno- 

 pliyllum-ZoTiQ of the South-Western Province. 



Chonetes. 



Convex papilionaceous Chonetes. 



The fragmentary nature of the specimens which have been col- 

 lected from the JRush sequence forbids any more definite determination. 

 This circumstance is much to be regretted, since, with the valuable 

 help of Mr. T. F. Sibly, I have been carefully studying the mutation 

 of this group, from early JSyringothyris-time up to its acme of 

 development in the Lower Dibunophyllum-Zone. The investigation 

 depends upon the patient accumulation of specimens showing 

 the internal characters. The material that we have already collected 

 indicates the gradual change, from Orthothetoid convergence in 

 Lower Syringotliyris-tivaQ to the most pronounced Productoid con- 

 vergence in Lower -Dibunophyllum-time, as exhibited in Producti- 

 Chonetes (=Daviesiella, Waagen) aff. comoides i of the South-Western 

 Province. 



1 ' Petrificata Derbiensia : 1809, pi. xxxvii, figs. 7 & 8. 



2 ' Geology of Yorkshire' vol. ii (1836) pi. viii, figs. 11 & 12. 



3 ' Synopsis Carb. Limest. Foss. of Ireland ' 1844 pi. xx, fig. 13. 



4 A. Vaughan, Quart. Journ. Geol. Soc. vol. lxi (1905) p. 295. 



