308 Mr. R. Hovvse on the Permian System of the 



not, many years ago, refrain from pointing it out, and no state- 

 ment has been made since that invalidates this conclusion. 



This species is most abundant in the shell-limestone, and 

 occurs sparingly in many of the upper beds of limestone. 



22. Macrodon striata, Schloth. — The form of the teeth of 

 this shell agrees with that of Macrodon, Lycett and Morris, and 

 the general shape is also very similar. The hinge-area is often 

 very much developed in specimens whose growth is somewhat 

 stunted round the free margins of the shell. This is the form 

 best known in England [Area tumida, Sow.) . The regularly-grown 

 shell is one of the most beautiful, both in form and ornament, of 

 those from the Permian rocks. The smooth or partially smooth ex- 

 amples, A. Kingiana, can often be traced on the umbonal regions 

 of genuine M. striata. The specimens figured in the ' Perm. Mon.' 

 give a very poor idea of the shape and beauty of ornamentation 

 of this common species. 



In the shell-limestone, rather common at Tunstall, and occur- 

 ring frequently in all the localities mentioned in the Table. It 

 appears to be a much commoner species in England than in 

 Germany. 



23. Leda speluncaria, Geinitz. — It is not to be disputed 

 that Geinitz's figure and short description of this little shell 

 have priority over Mr. King^s : therefore I feel no hesitation in 

 adopting it, although it is placed among the synonyms in the 

 ' Perm. Monograph.^ It occurs rather sparingly in the upper beds 

 of limestone, and more rarely in the shell- and compact-lnnestone. 



The Nucula Tateiana, King, is mentioned here that it may not 

 be lost sight of. It is impossible to adopt it as an authenticated 

 species, for, according to Mr. King's own words, the description 

 is drawn up from " the dorsal half '^ of a specimen only. Baron 

 Schauroth has favoured me with some specimens of a true Per- 

 mian Nucula [N. Beyrichii) from the zechstein of Germany ; and 

 this renders it very likely that on some future occasion specimens 

 may occur in our limestone. 



24. SOLEMYA NORMALIS, HoWSC. PI. IV. fig. 7 *. 



"Shell transversely oval, narrow, slightly arcuated; beaks in- 

 distinct near the posterior end ; anterior [much) elongated ; mus- 

 cular impressions large, slight ; a few raised lines diverging from 

 the beaks to the free margins on the cast ; external surface smooth." 



I obtained a single left valve of this very rare shell on a block 

 of Humbleton Hill shell-limestone, on Good Friday, 1845. 

 I afterwards described it, in the above words, in the Tyneside 

 Catalogue. It was there pointed out, that though it bears a 

 slight resemblance to S. biarmica, yet the beak is nearer 



* The figure in the accompanying plate does not represent the rounded 

 appearance of the anterior extremity as correctly as could be desired. 



