(i) 22 Pcdfcontdlofiia Siiiica Ser. B 



Shan, Shih-mnn-cliai (Shihmenchai) region near Cliingwangtao eastern Ghibli province 

 (horizon F3). The formation is Lo\ver Ordovician. 



Ophileta squamosa Grabau (sp. nov.) 



Plate II Figs 3-6 



Sliell with sunken spire, the whorls nearly in a plane but asymmetrical, gradualh' 

 enlarging and in contact except, in some eases, in the last part of the final whorl. 

 Umhilicus very large. Whorls with a gently concave, shghtly inward sloping shoulder, 

 limited within hy a blunt angulation and without l)y a ratlier sharp carina or keel, which 

 is however not greatly elevated. Outer surface of \A'horl regularly convex, in such a 

 manner tliat seen from al)Ove the carina is something less than one third of the width of 

 the whorl within the peri]ihery. Lines of growth curving strcMigly backwards at the 

 carina, forming a pronounced apertural notch at that point. 



On the umbilical side the whorls are gently convex or slightly angular at the 

 center with a pronounced Ijut rounded carina next to the inner margin. On this side the 

 lines of growth are very squamose projecting at regular intervals, in the adult, in the form 

 of small sharp varices. These die away at the outer margin, but continue on tlie inner 

 carina and along the inside of the whorl to the point of contact with the preceding 

 whorl. Preceding tlie strongly scjuamose portion of the final whorl is a part where these 

 sc[uamte have m(n'e the a}ipearanc(.' of cost;e and are farther apart (plate II fig 4). This 

 condition is still shghtly visible on a portion of the prece<ling whorl. 



The largest adult individual of this species found (pi. II fig. Ci), lias a maximum 

 diameter of 8S mm. It is ho^\'ever a much A\'orn S])ecim(_'n, and little can be added to the 

 characters. The width of the final whorl of the a[H.'rture is 15.') mm., the enlargement 

 being rather rapid in the last stage. The growth lines are strongly squamose projecting 

 about. 0.7 mm. from the sheU. 



A section of another adult shell has a dianu'ter of iJC) mm,, Ijut shows only the 

 outer whorl (pi. II. fig. 5), the maximum diameter of which is 12 mm., this being some 

 distance behind the ])eristome. The outer surface of the shell is regularly rounded, from 

 the keel of the shoulder angle to the margin of the umbilicus which is characterized hy a 

 faint rounded keel. The shoulder angle or keel lies about one tliird the distance in from 

 the periphery of the whorl as seen from aljove and it forms nearly a right angle. The 



