Counties of Durham and Northumberland. 309 



the posterior end, and the shell is much narrower than in the 

 Russian species. The anterior is also more elongated, and the 

 surface is quite smooth. It is also very much smaller. All 

 these differences are borne out by another single left valve lately 

 found by Mr. Kirkby at Tunstall. 



Mr. King had the loan of the above specimen for several 

 months ; and I find he has, in the ' Perm. Monog./ attempted to 

 describe and to figui'e a species which he identifies with this. 

 But he has succeeded very badly, both in the description and in 

 the figure, which does not represent my species. Baron Schauroth 

 has attempted, in one of his excellent papers, to identify a German 

 specimen with Mr. King^s description and figure; but he found 

 so little character in the latter, that he was obliged to leave the 

 matter in doubt. Certainly the S. PhilUpsiana, King, is not 

 worthy to be considered even a synonym. 



Two left-valves have been found in the shell-limestone of 

 Tunstall and Humbleton. 



25. SoLEMYA ABXORMis, Howse. PI. IV. figs. 8, 9. 



" Shell transversely oval; beaks not prominent ; posterior short, 

 narrow, rounded; anterior elongated, rounded, much wider than 

 the posterior ; surface slighthj waved concentrically, plain ; muscu- 

 lar impressions obliquely placed, deep." 



So difi*erent did this Solemya seem when I first described it, 

 that I never for a moment thought of drawing a comparison 

 between it and the S.biarmica ; and although I have received some 

 fine casts of German specimens of the latter, I must own that I 

 cannot identify them with either of the above species. The S. 

 abnormis is very pointed posteriorly, and the anterior is much 

 produced and very broad. It is also much flattened, and all the 

 specimens I have examined are quite smooth. The German casts 

 are rather tumid, slightly arcuated, and have the valves rounded 

 and covered with strong lines of growth near the anterior mar- 

 gin. It is therefore very doubtful whether the shells placed as 

 synonyms in the Table are referable to this species. 



It cannot certainly be referred to the >S. biarmica, Veru., of the 

 Russian Permian rocks, until it be known whether that species 

 really is a gaping shell or not. With these uncertainties, I 

 hesitate to alter the name originally given to it in the Tyneside 

 Catalogue. 



It remains to be stated, that Mr. King identifies this species 

 with the S. biarmica ; but the figure given in the ' Perm. ]\Ion.' 

 pi. 16. fig. 7, represents no Solemya, but a young specimen of 

 the Allorisma elegans. King. 



I have taken specimens of the above shell at Whitley, in the 

 compact-limestone; at Tunstall and Silkworth, in the shell- 

 limestone; and Mr. Kirkby has recently obtained a specimen 

 from Humbleton. 



