NORTHUMBERLAND AND DURHAM. 247 



of Sclilotlieim's 0. speluncaria appears to exist, that name should 

 be suppressed." ]\tr. King has, however, upon Goldfuss's autho- 

 rity, again revived it; hut until some figure of it, or some de- 

 scription or specimen can he shown, we have no right to adopt 

 an apocryphal name. 



3. CRANIA, Retzlus. 

 1. 0. KiRKBYi, Davidson. 



This Crania, recently found by Mr. Kirkby at Tunstall Hill 

 and Humbleton quarries, will be described and figured by Mr. 

 Davidson in the forthcoming part of his work on the British 

 Permian Brachiopoda. The discovery of this Crania is of con- 

 siderable interest, for though several species of Crania have been 

 found, both in the older and newer formations, until the present 

 the genus was quite unknown in the Permian System. 



4. PRODUCTUS, Sorverhy. 

 1. P. HORRiDUS, Sowerhy. 



The exterior of this shell is now very well known through the 

 numerous figures and descriptions of it which have from time to 

 time been published by several authors, but the interior has up 

 to the present period never been correctly delineated. Through 

 the kindness of Mr. Davidson, I am, however, furnished with 

 four proof-plates of Permian fossils, and favoured with permis- 

 sion to make references to them, in one of which the interior of 

 this species is for the first time faithfully represented. 



In the shell -limestone of Humbleton this species generally 

 occurs in casts, on which all the permanent structures of the 

 interior of the shell are faithfully impressed. One can, by a 

 study of these casts alone, restore and represent all the im- 

 portant characters of the interior; but in addition to these 

 casts, one frequently finds at Tunstall the shell itself, showing 

 the interior as perfectly preserved as in recent shells. It is, 

 therefore, rather a matter of surprise that no better figures of 

 the interior of this shell have yet been published. Mr. King 

 figures a gutta-percha cast of the interior of one valve only, and 

 that one, judging from the specimens that I have examined and 

 compared with it, very incorrectly. This will best be proved 



