Vol I. Grabau — Ordovician Fossils from North China (i) 31 



tendency towards a decreasing amount of embracing in the adult, which in certain cases 

 is followed by a loosening or laxness of the coil. 



Genotype: Pagodispira derwiduii Grabau, Ordovician. 



Of foreign species referable to this genus, we may mention Pagodisinm bowdeni 

 (Safford) from the Upper Ordovician of North America. So far as known the genus is 

 confined to the Ordovician. 



Pagodispira derwiduii Grabau (sp. nov.) 



Plate III Fig. 11. 



Shell slender, with the apical angle varying from 28 to 32 degrees; whorls 8 to 

 10 (at least 9 in the holotype) angular, and divided near the center of tlio exposed part 

 by a sharp peripheral carination ^\•hich consists of a median strong rounded spiral, closely 

 flanked by a fainter and much weaker spiral on each side. Shoulder gently concave, 

 apparently smooth, though there is a suggestion of faint spiral lines. Shoulder angle 

 varying from about 95 degrees in the young, or in more retarded individuals, to about 

 112 degrees in the adult. Exposed portion of -whorl below the shoulder angle of the same 

 flidth as the shoulder, and like that gently concave. A lower carina, situated just below 

 the suture of the whorls is present at least in the adult portion, where it is of moderate 

 strength on the body-Mhorl. Umbilicus covered by reflexed inner lip. Length of 

 holotype about 35 mm. (the apex is imperfect), diameter of last whorl 14 mm. 



This species differs from the American P. hoicdrni (Safford) {Lopltospira hoicdenl 

 Ulrich and Scofield) from the Lorraine and Richmond of the central United States, in 

 the sharper shoulder angle (that of P. hoivdeni being from 122 to 125 degrees) and in the 

 more strongly concave shoulder, that of P. bowdeni becoming convex near the suture, 

 forming an obscure carina. The whorls of our species also embrace to a lesser degree 

 than is the case in P. bowdeni, where the part below the periphery is only about two 

 thirds as wide as the shoulder. Finally the Chinese species has a sharper peripheral 

 carina and a stronger lower carina, the latter in P. bowdeni being faint or absent. From 

 P. dorothea Grabau, it differs in the sharper shoulder angle and peripheral carina and the 

 lesser degree of embracing. 



HoKizoN AKD Localities: In the Machiakou or Actinoceras limestone near 

 Chaokouchuang in the Kaiping coal basin, Chihli province. Collected by the Survey 

 expedition. Also in the same horizon at Tangshan, collected by George B. Barbour. 



