Dr. F. A. Bather — Studies in Edrioasteroidea. 59 



distal end, nearer the horizontal at the proximal end, hut they may 

 he compressed and flattened at the extreme distal end. Oral face 

 and spines not observed. 



Holotype. — The original of Aurivillius' plate-fig. 11 is hereby 

 selected. It is in the Riksmuseum, Stockholm. The holotype of 

 Scalpettum varium is the unique original of Aurivillius' plate-fig. 12. 

 The original of Aurivillius' plate-fig. 10 is hereby selected as holotype 

 of S. fragile; it is not the specimen measured. The holotype of 

 S. strobiloides is the unique original of Aurivillius' plate-fig. 17. 

 The specimen measured by Aurivillius (p. 16) is hereby selected as 

 holotype of 8. granulatum ; the figures may or may not be taken from 

 this. All these specimens also are in the Riksmuseum, Stockholm. 



Horizon. — Bed c ( = Wenlock Shale), Middle Silurian. 



Locality. — Djupvik in Eksta, also at Mulde and near Wisby, 

 Gotland, Sweden. 



P. proceea. Aurivillius sp. 



Scaljoellum procerum Auriv. 1892, p. 18. 



A Pyrgocystis with turret almost cylindrical, its diameter in the 

 proximal region about one-third of its total height, which is not 

 less than 10 mm. ; turret-plates in at least 25 tiers of 4 plates 

 in each, which alternate regularly, forming 8 columns separated 

 by faint grooves ; the width of each plate appears to be greater than 

 its height ; amount exposed fully one-half, its margin an arc of 

 a circle ; each plate is slightly bent on its vertical axis. The slope 

 of the turret-plates approaches the vertical in all the portion 

 preserved. Oral face and spines not observed. 



Holotype. — The original of Aurivillius' plate-fig. 15 is hereby 

 selected ; it appears to be the specimen measured (p. 18). It is in 

 the Riksmuseum, Stockholm. 



Horizon. — Bed c ( = Wenlock Shale), Middle Silurian. 



Locality. — Aurivillius gives a) near Wisby, b) Djupvik in Eksta. 

 I do not know from which of these the holotype came. 



P. cylindrica Aurivillius sp. 

 Scalpellum cylindricum Auriv. 1892, p. 18. 



A Pyrgocystis with turret almost cylindrical, its diameter not more 

 than one-third of its total height, which is not less than 9 mm. ; 

 turret-plates in at least 12 tiers of 4 plates in each, which 

 alternate regularly, forming 8 columns, which are not separated 

 hut closely inosculate ; the width of each plate is very little (if at all) 

 greater than its height ; amount exposed about two-thirds, its margin 

 a pointed arch. The slope of the turret-plates approaches the 

 vertical in all the portion preserved. Oral face and spines not 

 observed. 



Holotype.— The unique original of Aurivillius' plate-fig. 16, in 

 the Riksmuseum, Stockholm. 



Horizon. — Silurian, precise bed unknown. 



Locality. — Near Wisby, Gotland, Sweden. 



