VI. Pyrgocystis. 



1915 59 



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

 be 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 

 Scalpellum 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 S. 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. peocera. Aurivillius sp. 

 Scalpellum 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 

 but 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. 



