﻿Yol. 64.] CARBOXIFEROTTS LIMESTONE OF THE MIDLAND AREA. 47 



typical form, very large and thick-shelled, with highly-irregular 

 fine ribbing and a longitudinally-wrinkled shell, occurs abun- 

 dantly. Comparatively-small forms, with slightly-differentiated 

 wings and strong well-spaced ribs (= Productus edelhurgensis^ 

 Phil.), are extremely common. Small transverse forms, closely 

 approximating to Pr. latissimus. Sow., are not infrequent. 



Productus corrugatus is rare, but a large form of Pr. corrugaio- 

 Jiemisphencus is locally common. Typical specimens of Pr. hemi- 

 spliericus occur very rarely. 



Big specimens of Productus semiretlculatus, exhibiting many 

 varieties of form, are generally common, and locally very abun- 

 dant. Pr. costatus is rather rare. 



Productus concinnus and Pr. Martini always occur, and are 

 locally abundant. 



Productus scabr'iculus is generally rare, but in certain localities 

 typical specimens are abundant. Pr. punctatus always occurs, 

 though it is never very common. 



Productus longispinus and its allies, including Pr. aff. lohatus 

 and Pr. aff. setosus, range throughout the greater part of the 

 subzone, and are common locally. 



Ohonetes compressa^ a well-defined papilionaceous type, is 

 characteristic of this subzone, and, while usually uncommon, 

 attains great abundance in some localities. 



All the other brachiopods recorded in the list are either rare 

 or very localized in occurrence. 



Variation of the Fauiial Facies of the Lonsdalia-^whzowe. 



In the foregoing account the faunal lists include all those corals 

 and brachiopods that I have recorded in the Lonsdalia-svibzone 

 of the Midland area, exclusive of those species which are confined to 

 the ' brachiopod-beds ' (see below) ; while the analysis of faunal 

 characters also deals with the subzone in its normal development. 

 The term ' normal development ' is here employed to define that 

 generally-prevalent facies of the subzone in which the coral-fauna 

 and the brachiopod-fauna are about equally predominant, as opposed 

 to the abnormal, localized facies of the subzone (the ' brachiopod- 

 beds'), in which an enriched brachiopod-fauna predominates almost 

 to the exclusion of the coral-fauna. 



A study of the faunal facies of this subzone in the Midland area 

 reveals the following outstanding features: — (1) The distinctness 

 of a localized brachiopod-facies, apparentlj'- confined to the western 

 part of the area, from the generally-prevalent coral-and-brachiopod 

 facies. (2) A subsidiary change of facies, within the latter, typical 

 development. 



We will first consider that change of facies which is found within 

 the ' normal development ' itself, proceeding afterwards to a dis- 

 cussion of the ' brachiopod-beds.' This change is shown by a 

 marked difference between the faunal assemblage in the eastern 



