294 Proceedings of the Royal Physical Society. 



the specimens in question, that they could be no other than 

 my father's Productus Clarkei, and identical with the well- 

 marked fig. 23. Holding this in view, I forwarded my notes 

 and specimens to Mr Davidson, and after a lengthened corre- 

 spondence, and the production of satisfactory evidence, I 

 was able to convince him of the identity of his Strophalosia 

 Woodsi (m. s.) and >S^. Clarkei (Etheridge). 



It is hardly necessary to compare S. Clarkei with other 

 described species, except S. Gerardi (King). This will be 

 done in connection with the description of that species, 

 and there will then be discussed the possibility, first sug- 

 gested by Professor W. King, and concurred in by Mr 

 Davidson, of the latter's S, Woodsi being identical with 

 S. Gerardi (King). 



IjOc. and Horizon. — Pelican Creek, five miles north of 

 Sonoma Station; Pelican Creek, opposite Palmer's Old 

 Station; Parrot Creek, four and a half miles up (Marine 

 Series, Nos. 3, 10, 21, 36, 135, 138, etc., etc.). 



Collector. — E. L. Jack, Esq. 



Strophalosia Gerardi— King (?).— PL XII., figs. 34-37 ; 

 PI. XIII., fig. 38. 



8. Gerardi, King, Annals Nat, Hist., 1846, xviii., p. 93. 



„ De Koninck, Mon. Productus et Chonetes, 1847, p. 137. 



, , Mon. Permian Foss. England, 1850, p. QQ, t. 1 9, f. 6 and 7. 



,, Davidson, Mon. Brit. Foss. Brachiopoda, Introduction, t. 8, 



f. 211. 



Sp. Char. — Shell large, ovato-rotund, at times becoming 

 almost deltoid, strongly concavo-convex; ventral valve con- 

 vex, most so about the umbonal and visceral regions ; umbone 

 prominent, rounded, and overhanging the area to some extent ; 

 dorsal valve very concave, following closely the contour of 

 the ventral, assuming a more or less deltoid form, usually 

 much longer than wide ; hinge line short, not as wide as the 

 shell; area broad and well marked, elongately triangular; 

 deltidium conspicuous, convex ; surface of the ventral valve 

 concentrically laminated, and giving rise to numerous ad- 

 pressed tapering spines, which, when worn off, leave the 



