﻿536 ME. F. E. C. EEED AND PEOF. S. H. EETXOLDS OK- [NoV. I908, 



abundance of certain species has been frequently considered an 

 indication of the age of the beds ; but the sporadic occurrence of 

 many in this area, coupled with the local prevalence of certain forms 

 and the rarity of others, suggests that differences of environment 

 exercised the predominant influence. For example, the typical 

 Upper Llandovery Pentameriis ohlongus is very rare, although in 

 places a real May-Hill assemblage of fossils is present, including such 

 si^teciesas Palceocyclus 2^j'ceacutns, Strojpliomena compressa^ CopJospira 

 hemis2?herica, etc. The curiously-irregular local distribution of the 

 brachiopoda in the Llandovery was long ago noticed by Murchison. 

 The negative evidence furnished by the scarcity or absence of such 

 forms as Meristella crassa and M. angustifrons may be of more than 

 usual value, owing to the very large number of fossils examined and 

 the variety of the localities from which they have been obtained. 



If Codospira Tiemispherica is truly restricted to the Upper 

 Llandovery, as Murchison believed, we have to acknowledge that its 

 practically-ubiquitous presence forbids us from regarding any of the 

 fossiliferous Llandovery beds as belonging to the Lower division. 



With regard to certain less widely-distributed species, there is 

 a form which appears to be a variety of Chonetes striatella ; 

 it occurs at Damery Bridge and elsewhere. We are accustomed 

 to regard this species as typically a Ludlow one, but Murchison 

 mentioned it from May Hill. 



In the case of the long-ranging Rhynclionella nucula, it is quite 

 possible that we may be dealing with examples of homoeomorphy, 

 although, in the absence of knowledge of the internal characters of 

 specimens from different horizons, we cannot affirm that such is the 

 case. 



Eegarding the Llandovery fauna of this area as a whole, we 

 must admit that, despite certain local peculiarities and especially 

 deficiencies, it has the stamp of the Upper division. The occasional 

 presence of Wenlock forms suggests in places transitional beds. 



Wenlock. 



In the case of the Wenlock fauna, we note the comparative rarity 

 of trilobites and of recognizable genera of crinoids ; the abundance of 

 Eallia mitixda ; the presence of certain locally-peculiar brachiopods 

 (such as Stropliomena Waltoni) ; the abundance of certain others 

 elsewhere rare (as, for example, Rliynchonella Davidsoni and Ortliis 

 hascdis) ; and the absence of a host of species, especially among the 

 corals, crinoids, and brachiopods, which usually are prominent. 



The occurrence of Strophomena compressa at several localities 

 amidst a fauna with a Wenlock facies extends the known vertical 

 range of this species, for Davidson does not record it above the 

 Upper Llandovery. 



The whole facies of the Wenlock fauna in this area is somewhat 

 peculiar, and the rich and varied assemblage of organisms which 

 we are wont to associate with the typical Wenlock development is 

 wanting. But, from the succession and from the lithological cha- 

 racters of the beds, it may be inferred that the shallower or more 

 muddy water was an important factor in determining the features 

 of the local marine fauna. 



