102 PERMIAN FOSSILS. 



Strophalosia Morrisiana occurs rarely at Tunstall Hill, Tynemoutli Cliff (in Breccia), 

 Claxheugh, Dalton-le-Dale, Ryhope Field-House Farm ; and rather commonly at 

 Humbleton Q,uarry. A specimen, in the York Museum, of apparently the same 

 species, was found at NosterjS.eld. I suspect it also occurs at Ferry Bridge (vide 

 Phillips in 'Philosophical Magazine,' N. S., vol. iv, p. 401, 1828). In Germany it 

 occurs at Milbitz and Corbusen (Geinitz, ' Versteinerungen,' p. 16). Unless some of 

 the fossils assigned to its related form {Stropkalosia Cancrini) be the same, it would 

 appear to be absent in the Permian deposits of Russia. 



Strophalosia parva, Kin^. Plate XII, fig. 33, 



Diagnosis. — Form irregularly circular marginally. Large valve somewhat convex : 

 umbone very small, and much impressed : spines numerous, long, and closely packed : 

 area very small. Rarely exceeding a quarter of an inch in diameter. 



I have felt considerable difficulty in deciding whether this is the young of any 

 of the former species, or a distinct one ; but after a careful examination of a number 

 of specimens, I have been led to adopt the latter conclusion. Strophalosia Morrisiana 

 and 8. Goldfussi are the only species to which it is likely to be referred ; but its 

 umbone is much more impressed, and its spines are decidedly more numerous and 

 more elevated, than in the first : with Strophalosia Goldfussi the present species agrees 

 somewhat in the profusion and direction of its spines ; but in the former the umbone, 

 although very much impressed, is more prominent. 



Its habit of adhering to the inside of other shells (generally Productus horridus) 

 has already been noticed. The umbone (vide Plate XII, fig. 33 a) is the part by 

 which the shell was attached : the spines in this region were also thus subservient, as 

 proved by their mode of spreading over the inside of the shell to which they adhered, 

 and following its curvature : the remaining spines, those on the frontal slope of the 

 valve, were free and straight ; they also struck off from the surface of the valve at a 

 considerable angle, and extended considerably beyond its margin, — all of which 

 characters are fully displayed on a specimen which I have lately procured, but at too 

 late a period for its being figured in the present work. 



Strophalosia parva has only occurred to me in the shelly limestone of Humbleton 

 Quarry. 



1 I cannot conclude the Productidce without noticing an observation of Dr. Thomson's, leading to the 

 belief that Mr. James Sowerby had recognised nearly all the species of this family herein described : " Mr. 

 Sowerby considers that he is able to distinguish no fewer than casts of five species of Productus in the 

 specimen which I brought from Humbleton Hill." (Annals of Philosophy, vol. iv, p. 18, 1814.) 



