410 Prof. T. R. Jones and Dr. H. B. Holl on the 



above, tumid below. Slight marginal rim traceable in some 

 specimens. This is near F. umbilicata, but is squarer, thicker 

 ventrally, and always more or less reticulated. 



In Smith Coll. no. 69, Woolhope (poor variety) ; no. 76 (part), 

 Lincoln Hill, Ironbridge. Vine Coll. XXVii, bed no. 46 (a 

 variety); xxYilli.g.s, bed no. 46; LXV12, Shales over the 

 Wenlock Limestone ; and LXVii, bed no. 46 (including a 

 variety). 



12*. Primiiia valicla^ var. hreviata, nov. 

 (PI. XIV. figs. 8 a, 8 h.) 



Proportions :— L. 13. H. 9. Th. 8. 



This agrees with P. valida in all respects, except in being 

 smaller and relatively shorter, and not showing the central 

 depression. 



Vine Coll. xxvii,2,3, bed no. 46 ; LXV12 (part), Shales over 

 the Wenlock Limestone. 



12**. Primttia valida^ var. anqustata, nov. 

 (PI. XIV. figs. 4 a, 4 i.) 



Proportions :— L. 14. H. 8. Th. 6. 



In this the relative height and thickness of the valves are 

 much less than in the two foregoing forms ; otherwise the 

 features are closely similar. The usual depression on the 

 valves is here subcentral, towards the antero-dorsal region, 

 and is more open and undefined. 



Vine Coll. XXVIII4, bed no. 46 ; LXV13 (part)j Shales over the 

 W^enlock Limestone. 



13. Pnmitia tersa, Jones and Holl. 



Primitia tersa, J. & H., Ann. & Mag. Nat. Hist. ser. 3, vol. xvi. 1865, 

 p. 421, pi. xiii. figs. 3 a, b, c. 



Proportions :— L. 14. H. 9. Th. 9. 



This occurs at the railway-cutting, side of Severn, Iron- 

 bridge, no. 78, Smith Coll., with a quite or nearly smooth 

 surface; but a reticulate variety occurs in no. 78, Dudley 

 Tunnel. 



14. Primitia umbilicata, Jones and Holl. 



Primitia umbilicata, J. & H. op. cit. p. 420, pi. xiii. figs. 2 a-d. 



Proportions :— L. 15. H. 11. Th. 9. 



This occurs as a reticulated variety in the Smith Collection, 

 no. 73, railway-cutting, side of Severn, Ironbridge, and no. 77, 



