PLATE III. 



(Permian Species.) 

 Fig- 

 1 — 4. Strophalosia Goldfussi, Miinster. Young shells, from Tunstall hill, in the collection of Mr. 



Howse. 

 5, 6. — — Internal casts, from Ryhope-field House. 



7. — — Internal cast of the ventral valve, natural size. Humbleton ; in the 



collection of Queen's College, Galway. This specimen exhibits 

 the ordinary condition in which the internal casts are preserved ; 

 the adductor impressions are indicated, but no trace of the cardinal 

 muscular ones can be perceived. 



8. — — - External cast of the dorsal valve, from the same specimen as fig. 7, 



but enlarged. This specimen was figured by Professor King in 

 his ' Monograph,' pi. xi, fig. 9 ; but my drawing shows more 

 clearly the manner in which the quadruple impression of the 

 adductor is disposed, and how the reniform impressions divide 

 each pair. 

 9,10. — A remarkable internal cast, from Humbleton, in my collection. Fig. 9 



shows the interior of the dorsal valve ; fig. 1 that of the ventral 

 one, in which the adductor (a) and cardinal muscular impres- 

 sions (k) are beautifully defined. 

 11, 12. — — Internal cast of the dorsal valve. Fig. 12 is a gutta-percha impres- 



sion, taken from the same, showing the articulation of the 

 valves, &c. 



13. — — A very much enlarged representation of the ventral valve, with its 



long slender spines, a small portion of the shell being removed to 

 show, on the internal cast, the adductor and cardinal muscular 

 impressions ; from specimens in the collection of Mr. Kirkby. 

 Humbleton hill. 



14, 15. — — ■ Interior of the ventral valve. Humbleton hill. Collection of Mr. 



Howse. 

 16, 17. — — A dorsal valve, from Tunstall hill; in the collection of Mr. Kirkby. 



Fig. 17 shows the remarkable internal margin peculiar to some 



young individuals. 

 18. — — S. parva, King. From an internal cast, natural size. It adheres to a 



cast of Productus horridus, from Humbleton. In the Museum 



of Practical Geology ; formerly in that of Mr. Howse. 

 19 — 22. Strophalosia Goldfussi 1 var. Lewisiana, De Koninck. Slightly enlarged; from Humbleton 



and Ryhope-field House. Fig. 19 is a cast of the interior of the 



dorsal valve ; 20 — 22 represent a testiferous specimen, of which 



the spines are broken. 

 23. — — var. Whitley ensis, King. This is the original specimen from Whitley, 



now in the collection of Queen's College, Galway, and the one 



from which Professor King published a gutta-percha impression 



in pi. xii, fig. 26, of his Monograph. 

 24 — 31. Strophalosia lamellosa, Geinitz, var. Morrisiana, King. From Tunstall hill. Collections of 



Professor King and Mr. Kirkby. 

 32—33. — — From Dalton-le-Dale. Collection of Mr. Howse. 



