﻿470 DR. A. YAUGHAN OX THE FAUNAL SUCCESSION [Aug. I908, 



From an examination of the specimens in the Gilbertson Col- 

 lection (British Museum), upon which Phillips founded his two 

 species expansa and planosulcata, I am inclined to differ somewhat 

 from Davidson's interpretation, which is excellently illustrated in 

 Dav. pi. xvi. Pigs. 4, 4 a, & 4 6 there appear to be typical 

 examples of Athyris expansa (see Phillips, ' Geol. Yorkshire,' pt. ii, 

 pi. X, %. 18). 



The type of Athyris planosulcat a is obviously a slightly abnormal 

 variety ; but, having priority of position both in Phillips's text and 

 plate, it must absorb A. expansa. I agree, therefore, with Davidson 

 in the matter of the forms which he refers to A. planosulcata in 

 pi. xvi ; but I consider that, in including fig. 4, he has rejected 

 Phillips's species A. expansa. 



Pigs. 17 & 18, pi. xvi, and fig. 4, pi. xvii, exhibit such peculiarity 

 of form and radial striation as to deserve specific separation. They 

 characterize the ' Knoll ' level of the Midlands, Yorkshire, etc., and 

 are doubtless extreme variants of A. planosulcata. 



ACTINOCONCHXJS (?). (PI. L, fig. 10.) 



This species is common in the chert-beds of the upper part of P. 



In shape and in its thick expansions it agrees with Actinoconchus 

 paradoxus, M'Coy, and the pedicle-valve has the same small pointed 

 beak. 



The peculiarity, illustrated in the figure of a cast of the brachial 

 valve, lies in the elongated pit which indicates a thick septal 

 projection. This character ^ and the absence of the strong radial 

 ridges appear to separate this form from Athyris planosulcata. 



Oethids. 

 Schizophoria. 



Spinous variant of Schizophoeia eesupinata (Martin). (PI. L, 

 fig. 7.) 



This variant is common in P, but specimens are fragmentary. 



The surface is covered with short spines, and growth-halts are 

 strongly marked. The area in the pedicle-valve is often very large 

 and Syringothyris-like, and when this is the case the beak is usually 

 curved to one side. The muscular scars are very deeply impressed. 



Study of a fine series collected by Dr. Wheelton Hind from P of 

 Congleton Edge has demonstrated how instable are the characters 

 of this gens at the top of the Avonian. 



1 Hall & Clarke ('Handbook of the Brachiopoda* Geol. Surv. N. Y 13th 

 Ann. Rep. 1893-94, p. 780) give the presence of a median septum in the 

 pedicle-valve as a character of the genus Actinoconchus, but cite no authority 

 for the statement. 



