270 NOTES ON THE PERMIAN SYSTEM OF 



first references in the " Perm. Monog." arc only base, catalogue 

 names, without either figure or description, and as such have no 

 right of priority. If due attention had been paid to this rule, 

 most of the flagrant errors which now disfigure the " Perm. 

 Monog." would have been avoided. 



The specimen which Mr. King has figured as Solemya hiarmica^ 

 De V^erneuil, Perm. Mon. pi. 16, fig. 7, is only a young specimen 

 of lunulata. This species belongs to the genus Myacites^ as re- 

 stricted by Morris and Lycett. 



It occurs very sparingly in the shell-limestone of Tunstall and 

 Humbleton. 



26. EDMONDIA, Koninch. 



1. E. ELONGATA, Howse. PI. XL figs. 10, 11, 12, 13. 



" Shell elongated oval; heahs 2'>i'ominenty near the anterior end; 

 anterior short and rounded; jjosterior elongated, the dorsal margin 

 on a line ivitli the beak; surface convex, covered with strong con- 

 centric lines of groivth; hinge tvithout teeth; umbonal cavity divided 

 longitudinally hy an elongated, thin, slightly curved visceral plate, 

 dejjending towards the cavity of the shell.'''' 



The above is the original description of this shell given in 

 " Tyneside Catalogue," vol. I. It points out one peculiarity of 

 this species and genus, which appears to be generally misunder- 

 stood by authors: — The shelly process situated in the umbonal 

 cavity is supposed to be a cartilage-plate, and to belong to the 

 hinge. In Mr. Woodward's excellent Manual, it is suggested, 

 with doubt, that the shells of this genus were furnished with an 

 ossicle. An examination of several cross-sections of shells be- 

 longing to this genus does not appear to substantiate this conclu- 

 sion. The shell, also, of most of the species is very thin, and the 

 valves are united by a strong external ligament, as a Permian 

 specimen from Germany, and some examples of the carboniferous 

 E. arcuata in my possession clearly show. It could not, there- 

 fore, require an internal cartilage of such a size. But these are, 

 I think, not cartilage-plates, but internal processes equivalent to 

 the subumbonal or spatula-shaped blade of the genus Pholas, 



