246 NOTES ON THE PERMIAN SYSTEM OF 



BRACHIOPODA. 



1. LINGULA, Bnujulo'e. 



1. L. CiiEDNERi, Geinitz. 



The form of tliis sliell as it occurs in the marl -slate of Durham 

 is perfectly oval, the breadth being about two-thirds of the 

 length. On our specimens the roll-formed elevation is not so 

 distinct as Geinitz represents it, but the height of the valve 

 increases from the posterior umbonal margin to about one-third 

 the length of the shell, whence it decreases gradually towards 

 the front, and more rapidly towards the sides. The lines of 

 growth are strongly raised, and much wider apart in front 

 than in any other part. 



This shell is finely preserved in the marl-slate at Ferry Hill, 

 where it is rather abundant. The largest specimen I have seen 

 is half-an-inch in length and five-sixteenths in breadth, but it 

 is generally very much less. Only one individual occurred with 

 both valves together, and that v/as found in the compact-lime- 

 stone a few feet above the marl-slate. Along with these, 

 numerous fragments of Fishes and specimens of Ccmleijntes 

 selaginoides constantly occur. 



I may be allowed to cpiestion the occurrence of this or any 

 other species of Lmgula in the underlying red sandstone, as 

 stated in King's Monograph on the authority of Prof. Johnston, 

 for this sandstone is a true coal-measure stratum. 



2. DISCINA, Lamarck. 

 1. D. KoNiNCKi, Geinitz. 



Very little can be added to the original description of this 

 shell by Geinitz. The German specimens appear to be of about 

 the same size as those occurring in England, and with the same 

 proportions. This Brachiopod has a greater vertical range in 

 England than any of the others, being found in the marl- 

 slate, compact-limestone, and shell-limestone ; it is also the 

 rarest. 



Geinitz observes, that as " neither the drawing nor description 



