460 



PERMIAN COMPACT LIMESTONES. 



[Ch. XXTTT. 



subject is very obscure, and after studying the phenomenon in the 

 Marston Kocks, on the coast of Durham, I found it impossible to 

 form any positive opinion on the subject. The well-known brecciated 

 limestones of the Pyrenees appeared to me to present the nearest 

 analogy, but on a much smaller scale. 



The fossiliferous limestone (No. 3) is regarded by Mr. King as a 

 deep-water formation, from the numerous delicate bryozoa which it 

 includes. One of these, Fenestella retiformis (fig. 495), is a very 



Fig. m. 



a. Fenestella retiformis, Schlot. sp. 



Syn. Gorgonia infundibuliformis, Goldf. ; Betepora ftustracea, Phillips. 



o. Part of the same highly magnified. 



Magnesian Limestone, Hnmbleton Hill, near Sunderland.* 



variable species, and has received many different names. It some- 

 times attains a large size, measuring 8 inches in width. The same 

 zoophyte, or rather mollusk, with several other British species, is also 

 found abundantly in the Permian of Germany. 



Shells of the genera Productus (fig. 496) and Strophalosia (the 

 latter of allied form with teeth in the hinge), which do not occur in 



Fig. 496. 



Fig. 49T. 



Producing horridus, Sowerby Lingula Crednerii. 



(including P. ealvus, Sow.) 

 Sunderland and Durham, in Mag- 

 nesian Limestone ; Zechstein 

 and Kupferschiefer, Germany. 



(Geinitz.) 



Magnesian. 



Limestone ; 

 Marl-slate Durham ; 

 Zechstein, Thuringia. 



Fig. 498. 



Spirifer undulatzis, 



Sow. Min. Con. 



Syn. Triogonotreta iindulata, 



King's Monogr. 



Magnesian Limestone. 



strata newer than the Permian, are abundant in this division of the 

 series in the ordinary yellow magnesian limestone. They are accom- 

 panied by certain species of Spirifer (fig. 498), Lingula Crednerii 

 (fig. 497), and other brachiopoda of the true primary or palaeozoic 



King's Monograph, pi. 2. 



