Counties of Durham and Northumberland. 473 



and the term " Cellular" is also perhaps less objectionable than 

 the term Concretionary. 



In the Section at p, 36, the " Upper yellow limestone," a, a, 

 ought to have been represented conformable to the beds beneath. 



Several errors have, I fear, crept into the nomenclature in the 

 Synoptical Table. I have corrected some of these in the remarks. 

 The specific names of the following species require either cor- 

 rection or confirmation, viz. Spirifer undidatus, Gej'villia antiqua, 

 Myacites elegans, Mijoconcha modiuliformis. The last-mentioned 

 species will also probably require to be removed from the genus 

 Myoconcha. 



On a future occasion I hope to make a few remarks on the 

 remaining portion of the fauna of the Permian System. 



EXPLANATION OF PLATE IV. 



Figs. 1, 2. Product us latirostratus, Howse, from the shell-limestone, 

 Dalton-le-dale. 



Fiffs. 3, 4. Camarophoria Humbletonensis, Howse, from the shell-limestone, 

 Humbletou. 



Figs. 5, 6. Spiriferina cristata, Schloth. sp., from the shell-limestone, 

 Tunstall. 



Fig. 7- Solemya normalis, Howse, from the shell -limestone, Humbleton. 



Figs. 8, 9. Solemya a6?jormis, Howse, from the shell-limestone, Silksworth. 



Figs. 10-13. Edmondia elongata, Howse, from the shell-limestone, Tun- 

 stall and Humbleton. 11. Cast showing fissure left by the sub- 

 umboual blade or plate. 12. Hinge-margin removed, showing 

 the form of the subumbonal blade. 



Figs, 14, 15. Tellina Duneltnensis, Howse, from the shell-limestone, Hum- 

 bleton. 



Figs. 16, 17. Calyptrcea antiqua, Howse, from the shell-Umestone, Tun- 

 stall. 



Fig. 18. Ckemnitzia Altenburgensis, Geinitz, sp. = Turritella Phillipsii, 

 Howse, from the shell-limestone, Tunstall. 



F^gs. 19, 20. Littorina helicina, Schloth. sp.; varieties with nearly obsolete 

 spiral bands, from the shell-limestone, Tunstall. 



Figs. 21-25. Pleurotomaria antrina, Schloth. sp. 23. Typical form and 

 varieties, from the shell-limestone of Silksworth and Dalton-le- 

 dale. 



Fig. 26. Nautilus Frieslebeni/}\i\.,Ge\mtz,ivovcit\ie shell-limestone, Silks- 

 worth. 



Fig. 27. Thecal Kirkbyi, n. s., from the shell-limestone, Tunstall. 



Fig. 28. Retepora Ehrenbergi, Geinitz, from the shell-limestone, Silksworth: 

 a, portion of the large individual figured in ' Perm. Mon.' t. 5. 

 f . 1 ; b, young individual ; c, fragment enlarged, showing inter- 

 stices and polype-cells ; d, fragment slightly enlarged, showing 

 the reverse or non-celluliferous surface. 



Fig. 29. Caryophyllia quadrifida, Howse, from the shell-limestone, Humble- 

 ton : a, c, coral-stem, natural size ; b, cast showing the position 

 of the laminae or plates. 



