Prof. W, King's Notes on Permian Fossils. 265 



vex ; evenly rounded ; often witli one or more contracted longi- 

 tudinal furrow-wrinkles on the sides, and furnished with a number 

 of long, rather distant, somewhat irregularly arranged, creeping 

 or adpressed spines directed forward : both inner and outer sur- 

 face marked with nearly obsolete stri?e radiating from the um- 

 bone; also with numerous well-defined incremental lines: umbone 

 slightly affecting the even roundness of the valve ; decidedly 

 impressed or truncated ; and scarcely curving down to the car- 

 dinal edge : area a little more in length than half the width of 

 the valve ; rather low, but well defined, being in the form of a 

 very obtuse triangle, the sides of which are about equal to |ths 

 of the length of the base ; faintly lineated transversely ; and fur- 

 nished with a narrow deltidium. Small valve slightly concave ; 

 here and there exhibiting a few nearly obsolete, slightly elon- 

 gated indented impressions a little raised at their anterior end, 

 which causes them to appear as if produced by a blunt-pointed 

 instrument : both inner and outer surface marked with fine 

 radiating striae a little more strongly marked than those on the 

 large valve : nucleus raised a little above the general surface of 

 the valve : area little more than rudimentary. 



All the specimens I collected of this species are a little under an 

 inch in width, and about f of an inch in length. The small valve 

 I am now strongly inclined to think cannot be considered as spi- 

 niferous : probably the nearly obsolete indented impi'essions may 

 be modified bases of abortive spines. In the Appendix to my 

 Monograph (p. 245) it is noticed, that this species has its small 

 valve furnished with spines ; and a reference was made to a cast 

 from Whitley represented under fig. 26. pi. ]2, which very 

 distinctly exhibits these structures ; but I now regard this spe- 

 cimen as belonging to the species next to be noticed*. 



The foregoing description may be considered as an amplifi- 

 cation of the diagnosis given in p. 160 of my Monograph ; — the 

 latter, however, is incorrect in some respects, caused by my 

 including in it certain characters exhibited by the Humbleton 

 variety. 



1 am not aware that this species has yet been found anywhere 

 except at Tunstall Hill. 



I shall next proceed to tabulate the difierences between it and 

 Strophalosia Cancrini, taking De Verneuil's figures and descrip- 

 tions as my guidef. 



* Vide Monograj)!!. In plate 11. fig. 21. is represented an ideal section 

 of Strophalosia Monisiana, which must be cancelled, as the spinous cha- 

 racter is altogether incorrect, and the large valve is too convex. 



t Geology of Russia, by Sir R. I. Miu-chison, De Verncuil and Count 

 Keyserling, pp. 273, 274. pi. 16. fig. 8, and pi. 18. fig. /• 



