PLATK XIII. 



Fig. Page. 



1. Onemidactis girvane7isis (Schuchert) ; photograph of the apical surface 



of a young specimen, x 0. — Upper Ordovician (Ashgillian) ; 

 Thraive Glen, Ayrshire. Mrs. Gray's Collection, no. D. 255 . 1G1 



2. Photograph of the side view of an arm of an older individual of the 



same species, x 3. Ibid. — Mrs. Gray's Collection, no. D. 125 . 157 



3. Protarthr aster longimanus (Whidborne) ; photograph of the apical 



surface, x 5. — Upper Devonian ; near Braunton, Devon. Museum 



of Practical Geology, Jermyn Street, no, 71G3 . .164 



4. Photograph of the oral surface of the same specimen, x 4 . . 104 



5. Ditto; photograph of the oral surface of another individual from the 



same horizon at Baggy Point, N. Devon, x 4. — Museum of 

 Practical Geology, Jermyn Street, no. 71G2 . . .160 



