﻿246 DE. A. VAUGHAN ON THE FALJ30NT0L0GICAL [May I905, 



Retzids. 



Eumetria : M and K^ 1 



Rhynchonellids. 



Camarotmchia. 



Species-group : CamarotcecJiia mitcheldeanensis (in- 

 cluding two or more mutational stages). Abundant 

 in M, K, and Z x ; rare in Z 2 ; very scarce in C. 



Orthids. 



(i) Schizophoria. 

 Species-group: Schizophoria resupinata. Very rare in Z r ; 

 abundant in the lower part of Z 2 ; rare in y. 



(ii) Rhipidomella. • 



Species-group: Rhipidomella aff. Michelini. Rare in K 2 ; 



abundant in Z (maximum probably at the top of Z ) ; 



rare in C. 



Strophomenids. 



(i) Orthotetes. 

 Species- group: Orthotetes crenistria. 



This group persists throughout the whole of the Carboniferous 

 Limestone ; but, whereas it is extremely abundant all through the 

 Tournaisian, it becomes comparatively unimportant in the Visean. 



The group undergoes well-marked mutational change, and the 

 following stages in mutation can be easily distinguished : — 



Mut. K x : maximum in K x ; extends into K 2 . 

 Mut. Z : K , Z, and C. 



Mut. C : Z 2 , y, and C. 

 Mut. S : S (chiefly SJ. 

 Mut. D : : S 2 and D r 



(ii) Leptena. 

 Species-group: Leptena analoga. Occurs in a; abundant 

 in K and Z ; unknown in C. 



Productids. 



(Very much more work must be done, both in the field and in the 

 laboratory, before the true inter-relationship of the several members of 

 this family and their ranges in time can be considered as satisfactorily 

 established in the Bristol area.) 



(i) Productus. 

 Species-groups : — 



(1) Productus bassus. Very abundant in K x ; doubtfully 



recorded from K 2 . 



(2) Productus cf. Martini (including variations towards 



Pr. hngispinus and Pr. semireticulatus). Abundant in 



1 A single specimen has been discovered near the top of K, in the Failand 

 section. 



