PLATE X. 



Fig- 



1. Cleiothyris pectinifera, /. de C. Sowerhy. Umbonal view (natural size) of a tes- 



tiferous specimen. Tynemouth Cliff. 



2. , — — Large valve of last specimen, showing the pectinated 



expansions. 



3. — — Small valve of the same, showing the emarginate 



foramen {a). 



4. — — Lateral view of the same, showing the pectinated ex- 



pansions. 



5. — — Cast of large valve, natural size. Humbleton Hill. 



6. — — Umbonal view of the last specimen. 



7. — — Magnified view of the pectinated expansions. 



8. — — Enlarged view of the inside of the posterior half, showing 



the hinge-structures of both valves : a, dental plates ; 

 3, foramen in the crural base or platform ; e, teeth ; 

 /, dental sockets. Humbleton Hill. 



9. — — Enlarged view of the hinge-structures of the small valve : 



a, crural base or platform ; b, foramen in do. ; c, button 

 or cardinal muscular fulcrum ; d, origins of the crura 

 of the spirals. 



10. — — Enlarged view of one of the spirals, showing it to be fringed 



on the outer edge. Humbleton Hill. 



1 1 . Martinia Clannyana, King. Cast, twice the natural size ; large valve. Ryhope 



Field-House Farm. 



12. — — Small valve of the last specimen. 



13. — — Umbonal view of the same, exhibiting area and fissure. 



14. Martinia Winchiana, ir2%y. Cast (enlarged) of large valve. Whitley. 



15. — - — Cast (enlarged) of small valve. Whitley. 



16. — — Umbonal view, showing area and fissure. Whitley. 



17. — — Restoration of the large valve. 



(I was formerly of opinion that in this species the valves were covered 

 with radiating hair-like spines ; bat of late I have been led to 

 think that the characters inducing this opinion, are merely due 

 to the fibrous structure of the shell. It is therefore extremely 

 doubtful that the shell possessed any spines as represented in 

 the restoration.) 



