PLATE XV. 



Fio. Page. 



1. Schuchertia laxata, Schuchert; photograph of the apical surface, X 2. 



— Upper Ordovician (Ashgillian) ; Thraive Glen, Ayrshire. Mrs. 

 Gray's Collection, no. D. 330. -212. 



2. Schuchertia wenlochi, n. sp. ; photograph of a portion of the oral surface 



to show detailed structure of the ambulacral groove, X 1<>. — Middle 

 Silurian (Wenlock) ; Gutterford Burn, Pentland Hills. Royal 

 Scottish Museum, no. 32/484. 215. 



3. Ditto ; photograph of an interraclial angle of the specimen figured 



PL XIV, fig. 5, X 3. 215. 



4. Ditto; photograph of a portion of the apical surface, X 2. — Ibid. 



Royal Scottish Museum, no. 32/480. 2K>. 



5. Palasterina primaeva (Forbes) ; photograph of the apical surface of one 



of Forbes' types, x 3. — Upper Silurian (Lower Ludlow, Bannisdale 

 Slates) ; High Thorns, Underbarrow, Westmoreland. Sedgwick 

 Museum, Cambridge, no. a/517 (slab d). 223. 



i). Ditto; photograph of the apical surface of another individual, X 4^.— 

 Bannisdale Slates ; P Underbarrow. Sedgwick Museum, Cambridge, 

 no. 48. 223. 



7. Ditto; photograph of the oral surface of another individual, X 4i. — 



[bid. British Museum (Nat. Hist.), no. E. 4991. 223. 



8. Eoactis simple,)', Spencer; photograph of the oral surface, X 4i.— 



Lower Ludlow or Upper Wenlock ; Hafod, Llandovery. British 

 Museum (Nat. Hist.), no. E. 13154. 206. 



9. Palasterina antiqua (Hisinger) ; photograph of the oral surface of 



young individual, X 41— Middle Silurian (Wenlock) ; Gutterford 

 Burn, Pentland Hills. Royal Scottish Museum, no. 32 L63. 228. 



M. = madreporite ; M.P. = mouth-angle plate; 0. = odontophor. 



