1915 58 F. A. Bather — Studies in Edrioasteroidea. 



Horizon.— Stictoporella bed, Decorah shales, Lower Ordovician. 

 Locality. — St. Paul, Minnesota, U.S.A. 



P. grayae n.sp. 



A Pyrgocystis with turret markedly tapering distalwards, its 

 diameter in the proximal region about one-fifth its total heigbt, which 

 is about 20 mm. ; turret-plates in about 80 tiers of about 5 plates 

 in each, which in the proximal region alternate regularly so as to form 

 about 10 columns; each plate appears to be probably wider than high, 

 and to have an outer margin shaped like a flattened arc of a circle ; the 

 amount exposed is uncertain. The turret-plates seem to be laid at 

 a steep pitch throughout; at the proximal end they form a distinct, 

 almost vertical-walled, kind of cup, from which springs the high- 

 domed oral face. Spines not observed. 



Holotype.— Collection of Mrs. llobert Gray, Edinburgh, K 8. 



Horizon. — Starfish bed, Drummuck series, Upper Ordovician. 



Locality. — Thraive Glen, Girvan, Ayrshire, Scotland. 



P. ansticei n.sp. 



A Pyrgocystis with turret slightly tapering distalwards, its 

 diameter in the proximal region about one-half to two-thirds its total 

 height, which is about 8 mm. ; turret-plates in about 50 (or fewer) 

 tiers of not more than 4 plates in each, which in the middle region 

 alternate regularly, often forming 8 distinct columns separated by 

 grooves; the width of each plate is from six-tenths to nine-tenths of 

 its height; amount exposed about one-fifth, its margin a parabolic 

 curve. The slope of the turret-plates in the fossils is nearer the 

 vertical at the distal end, nearer the horizontal at the proximal end. 

 Oral face and spines not observed. 



Holotype.— Brit. Mus., Geol. Dept., E 16235. 



Horizon. — Wenlock Shale, Middle Silurian. 



Locality. — Jig House Bank near Coalbrookdale, Shropshire, 

 England. 



P. sulcata Aurivillius sp. 



Scalpellum sulcatum Auriv. 1892, p. 13. 



Scalpellum varium Auriv. 1892, p. 15. 



Scalpellum fragile Auriv. 1892, p. 19. 

 ? Scalpellum strobiloides Auriv. 1892, p. 17. 

 ? Scalpellum granulatum Auriv. 1892, p. 16. 



A Pyrgocystis with turret slightly tapering distalwards, its 

 diameter in the proximal region about half (or a little less) of its 

 total height, which is about 11 mm.; turret-plates in about 50 

 (or fewer) tiers of not more than 4 plates in each, which alternate 

 regularly, often forming 8 distinct columns, separated by grooves; 

 the width of each plate appears [from Aurivillius' drawings; no 

 measurements are given] to be greater than its height; amount 

 exposed about one-fifth, its margin an arc of a circle. The slope of 

 the turret-plates in the fossils is nearer the vertical towards the 



