SCHUCHERTIA WBNLOCKI. 215 



r = 6 mm., R = 3r. The University of Chicago individual : \l — 23 mm., r = 

 about 8 mm., R = 2*8 r. Other specimens indicate a growth twice as long as the 

 former one." 



Horizon and Locality. — Upper Ordovician (Ashgillian) ; Girvan, Ayrshire 1 , 

 Scotland. The American species is from the Upper Ordovician (Richmond 

 Formation) of Ohio. 



3. Schuchertia ordinaria, Sclmchert. 



1915. Schuchertia ordinaria, Schuchert, Bull. 88, U.S. Nat. Mus., p. 199 (not figured). 



Material. — One specimen in the Gurley Collection of the University of Chicago 

 (no. 10992). Schuchert remarks — " The specimen cannot be freed of the adhering 

 clay sufficiently to make an instructive photograph, and is therefore not 

 illustrated." 



Specific Characters. — See p. 211. 



Description. — "The species is most closely related to 8. laxata, but is smaller 

 and with a comparatively larger disc. Therefore the rays do not protrude beyond 

 the disc so far as in the latter form. Abactinal skeleton consists of minute tumid 

 ossicles that are more cut along their edges than in 8. laxata and therefore more 

 spicular " (Schuchert, loc. cit, p. 199). 



Measurements. — R =11 mm, r = about (r3 mm. 



Horizon and Locality.— The basal Silurian Girardeau Limestone ; Alexander 

 County, Illinois, U.S.A. 



4. Schuchertia wenlocki, n. sp. Plate XIV, figs. 5, 6; Plate XV, figs. 2 — 4; 

 Text-figures 124 (p. 183), 127 (p. 187), 143 (p. 203), 145 (p. 204), L54— 156. 



L916. Schuchertia, u. sp., Speucer, British Palaeoz. Asterozoa (Mon. Pal. Soc.vol. for 1915), p. 67. 



Material. — Eleven specimens of the species are known, all moulds in sandstone 

 from the Starfish Bed of Gutterford Burn. They are in the Royal Scottish 

 Museum (nos. 1897, 32/475, 177, 478, 480, 482, 484, 485, 486, 487, 490, 491). 

 Specimen no. 485, a cast of which is photographed in PL XIV, fig. 5, is taken as 

 the holotype of the species. 



Specific Characters. — See p. 211. 



Oral Surface (PI. XIV, figs. 5, 6; PI. XV, figs. 2, 3; Text-fig. 154).- 

 Excellent oral views can be obtained from casts of 475, 484, 485, which show 

 almost the whole of the original specimens. Casts from 486, 487 and 491 show 

 the same surface but are more fragmentary. The reconstruction (Text-fig. 154), 

 is based mostly on a cast from 485, although details are added from other 



