﻿1861.] 



KXRKBY PERMIAN, SOUTH YORKSHIRE. 



303 



are not well preserved, being either casts of the interior, or impres- 

 sions left in the matrix after the decay of the shell. They are half an 

 inch or less in length, and are slightly curved, more so posteriorly than 

 towards the aperture ; they taper gradually, and have apparently 

 been smooth. 



Prof. King first described this species from a specimen discovered 

 by Mr. H. Clifton Sorby at Conisborough. 



More than a year ago I found a Dentalium in the Shell-limestone 

 of Durham, which evidently belongs to this species. It is testi- 

 ferous, of the same length, of similar curvature, and smooth like 

 the examples just noticed. It perhaps increases a little more rapidly 

 in width, and is more acuminate posteriorly than they ; but these 

 differences seem of little import. 



There does not appear to be much doubt as to this species being 

 identical with the Bent. Speyeri of Geinitz, which occurs in the Unter 

 Zechstein and Zechstein-Dolomit of Germany. Specimens from these 

 deposits, sent to me by Baron von Schauroth as those of B. Speyeri, 

 show little variation from English examples. And I have also 

 compared the latter with drawings of type specimens with which I 

 have been kindly favoured by Dr. Geinitz, but can detect nothing 

 that will constitute a specific difference. 



Loc. Hampole Stubbs, Conisborough (Sorby). 



CONCHIEERA . 



1. Gervixlia antiqtxa, Minister; Goldfuss, Petrefacten, part 2. p. 126. 



Syns. Bakevellia tumida, King ; Avicula inflata, A. Binneyi, and 

 A. discors, Brown. 



Two forms of this species occur in Yorkshire. One is longer 

 than wide, rather inflated, with a shallow curvature in posterior 

 margin, and a deep byssal sinus. The other is wider than long, 

 rather flat, and with a byssal sinus not so deep as the first. Neither 

 is found above half-an-inch wide, generally less. The surface of 

 both is marked with the regular, finely raised lines of growth so 

 characteristic of the species in Durham. 



The relative thickness of the shell appears to have been greater in 

 the Yorkshire individuals than in those of Durham. The muscular 

 impressions and pallial lines are thus often very clearly indicated on 

 the casts. The hinge-teeth are also very instructively shown in many 

 specimens. 



In one quarry near to Pickburn I obtained specimens of the more 

 elongate form which assume the character of the Bakevellia tumida 

 of King, — the valves being very tumid, the hinge-line of great width, 

 and the shell altogether more irregularly grown than in type speci- 

 mens of the species. 



G. antiqua occurs in immense quantities in the Lower Limestone, 

 associated with remains of other Gervillice apparently belonging to 

 the species keratophaga. At Bull Hill Quarry near Pontefract, and 

 at Wentbridge, their remains almost solely form thick beds of lime- 

 stone. It is almost invariably in the state of casts, and generally in 

 detached valves. 



VOL. XVII. PART I. Y 



