﻿Vol. 64.] IN- THE CAKBONIFEROUS EOCKS AT L0T7GHSHINNY. 447 



parts. Productus prohoscideus occurs only at one level, at the base 

 (L 5 d). 



Posidonomya abounds in the middle and upper parts (P. Becheri 

 being the first species to enter). 



Glyjpliioceras spirdle occurs only in the upper part. 



These facts have probably local value ; the brachiopod-fauna is, 

 however, so essentially similar throughout, that the subdivisions are 

 very indistinctly differentiated. 



On the other hand, the P-fauna is markedly distinct from that of 

 the Curkeen and Dihimophyllum-him.QsioDies (Lower D.^) : — 



(1) Many of the best-known and most abundant Visean gentes 



have dropped out, at least in their typical forms. 



Examples: 



Productus corrugatus, Productus hemisphericus, Athyris glahristria , 

 Lejptcena analoga, Syringothyris laminosa. 



(2) Other gentes show degeneration or excessive specialization. 



Examples : 



Michelinoid Favosites, Lonsdaloid Carcinophyllum, Konincko- 

 pTiyllum cf. inter r upturn, Athyris cf. planosulcata, Martinia glabra, 

 mut., Derhya grandis, Spiriferina insculpta, mut. 



(3) Others again indicate instability by the rapid production of 



several strongly-marked and differentiated variants. 



Examples : 



Schizophoria resupinata in its gigantic and spinous varieties. 



Martinia glabra in its great variety of form and in its convergence 

 with Martinia. ovalis. 



Spirifer aff . bisulcatus in convergence with several cognate species 

 and in highly ornamented varieties. 



(4) Certain genera which reach their acme in post-Avonian time 



become abundant for the first time. 



Camarophoria, Derbya. 



Occurrence of the most important P-Eorms in 

 other Areas. 



(In most cases a single outside locality is cited ; the instances 

 could, however, be multiplied many-fold.) 



(i) Corals : 



Michelinia tenuisepta, var. favositoides^ the ultimate stage 

 of M. tenuisepta, is common in D3 at Bradbourne (Derbyshire). 



Densiphyllids : — One type is common at Bradbourne, another 

 at Dunbar. 



Dendroid Lithostrotions are rare and consist, almost entirely, 

 of narrow forms, as is universally the case near the top of the 

 Avonian. 



Lonsdaloid Carcinophyllum has been found by Dr. Wheelton 

 Hind at Poolvash (Isle of Man) in the 'Knoll' Limestones. 

 Q. J. G. S. No. 255. 2 g 



