100 PERMIAN FOSSILS. 



(?) Producta spinosa, J. Sow. J. de C. Sowerby, Sedgwick, Trans. Geol. Soc, 2d series, 



vol. iii, p. 119, 1829. 

 (?) Producta longispina, Sow. De la Beche, Geol. Man., p. 384, 1831 ; Germ. Transl., 



p. 459, 1832; 3d Eng. Ed., p. 5/3, 1833. 

 Stuophalosia Morrisiana, King. De Verneuil, Bull, de la Soc. G^ol. de France, 



2""serie, vol. i, p. 30, 1844. 



— — „ Geol. Russ., vol. i, p. 222, 1845. 



— — „ King, Annals and Mag. Nat. Hist., vol. xviii, 



p. 28, 1847. 



— — „ King. Catalogue, p. 9, 1848. 

 Productus spiniferus. King. Howse, Trans. T. N. F. C, vol. i, p. 257, 1848. 



(?) Oethothrix lamellosus, Geinitz. Versteinerungen, p. 14, pi. v, fig. 16, &c., 1848. 

 Productus cancrini, De Vei-neuil. Op. cit., p. 16, pi. vi, figs. 17-18 a, b, 1848. 



Diagnosis. — " Form rounded. Both valves marked with numerous fine broken 

 lines radiating from the nucleus. Area wide, and slightly elevated. Dorsal valve 

 slightly convex/ irregularly wrinkled longitudinally on the side, with several spines, 

 rather long, adpressed and directed forward on the back, erect and directed backward 

 on the umbone and sides. Ventral valve somewhat concave. Umbone small and much 

 impressed."^ (King.) 



Strophalosia Morrisiana is undoubtedly closely related to the Russian species, 

 Strophalosia {Productus) Cancrini of De Verneuil ; but the following tabular comparison 

 will show that both species possess certain well marked distinctive characters. 



8. Morrisiana. 8. Cancrini.^ 



Slightly convex. Very convex. 



As -wide as long ; often wider. Longer than wide. 



Lateral slopes gradually inclining, and plicated Lateral slopes rapidly inclining, and plicated 



longitudinally. transversely. 



Area decidedly obvious. Area scarcely perceptible.* 



There appears to be some other differences, as in the striae and spines, and in the 

 form of the small valve ; but these I cannot insist on, in consequence of having no 

 specimens by me of the Russian, to compare with the English species. 



Two varieties of 8trophalosia Morrisiana occur in the Permian rocks of Durham. 

 One has the large valve slightly convex, with a very small umbone ; and appears to 

 be confined to Tunstall Hill (this variety is represented in Plate XII, figs. 18, 19) : in 

 the other, which is rather common at Humbleton Q,uarry, the corresponding valve 

 is more rounded, and the umbone more prominent (it is represented in the same 



^ Incorrectly printed in my ' Catalogue' " roundly convex." 

 2 Catalogue, p. 9, 1848. 



^ Vide Geol. Russ., vol. ii, pp. 273-5, pi. xvi, fig. 8 a, 6, c ; pi. xviii, fig. 7. 



* The area, which I presume exists, appears to be so small that it has escaped the observation of 

 M. de Verneuil. 



