PLATE IX. 



Fig. Paoe. 



1. Urasterella thraivensis, n. sp. ; photograph of apical surface of disc, 



X 5. — Upper Ordovician (Ashgillian) ; Thraive Glen, Ayrshire. 

 Mrs. Gray's Collection, no. D. Ill . . . .137 



2. Photograph of the oral surface of another specimen of the same 



species, X 3. — Ibid. Mrs. Gray's Collection, no. D. 254 . 138 



3. Urasterella ruthveni (Forbes), var. leintwardinensis, nov. ; photograph of 



the apical surface, X 3. — Upper Silurian (Lower Ludlow) ; Leint- 

 wardine, Herefordshire. Ludlow Museum, no. iv . . 143 



4. The same specimen, X 6 . . . . . 143 



5. Urasterella ruthveni (Forbes) ; photograph of lateral view of arm, x 4. 



— Upper Silurian (Ludlow) ; Bannisdale Slates, N. End of Benson 

 Knot. Sedgwick Museum, Cambridge . . .140 



