NORTHUMBERLAND AND DURHAM. 250 



CONCITIFERA. 

 13. TECTE^.O.F. jMuller. 



1. P. rusiLLUS, Schloth. 



The autlior of tlie " Perm. Monog." lias, in translating Gold- 

 fiiss's specific description of this little shell into his " Monograph" 

 and into English, made a little too free with the Latin original. 

 In the " Monog.," " antica valvar dextra^ majori subplicata," is 

 rendered " the fore part of the right valve in a great degree 

 snbplicatc." Now this is both contrary to fact and to Goldfuss's 

 German description, as well as to the Latin, and might lead to a 

 little confusion hereafter. 



This Pecten is described as smooth by all authors, and such 

 is its most general appearance ; but when the shell is perfect and 

 well preserved, there are to be seen all over its outer surface fine 

 stri^ of growth running parallel to the lower margin. Also on 

 many specimens numerous fine lines radiate from the umboncs 

 to the same margin. The hinge-line is furnished in some indi- 

 viduals with an area of comparatively great size, but generally 

 it is so small as not to be observable. 



Some specimens of a Pecten which are found in a peculiar 

 yellow conglomerate near Gera in Germany have lately been 

 elevated into a species by Baron Schauroth, under the name of 

 Pecten Macrothi. I have examined some fragments of this shell 

 obligingly sent to me by this learned Permian palaeontologist, 

 and I am sorry that I am obliged to consider the distinguishing 

 character which he has pointed out as not of sufficient value to 

 constitute a species. The chief character mentioned as peculiar 

 to this new shell is the distant, very flat lines of growth parallel 

 to the margin. But this is, as above stated, the perfect appear- 

 ance of the surfiice of Pecten j^^tsillus, to which the Pecten 

 Macrothi, I have no doubt, belongs. To this, also, must one 

 refer De Koninck's Pecten Geinitzianus, from the Spitzbergen 

 Permian rocks. 



This species occurs most abundantly in the shell-limestone of 

 Humbleton, and sparingly in all the other localities mentioned 



