(iv) 26 Patxontologiii Sinica Ser. B. 



"Surface smooth, with the exception of a few concentric striaj and lines of 

 growtli. 



"The ventral valve has a strong median sinus that occupies about one-third 

 of the width of the valve at the anterior margin and projects forward to fit into the fold 

 in the front of the margin of the dorsal valves; the sides of the median sinus are elevated 

 and, with the downward curving lateral slopes, form a strong rounded ridge on each side 

 of the sinus; none of the specimens in the collection show the area, but from the profile 

 of the valve it must have been of moderate height, with a rather short apex curving over it. 



"Dorsal valve with a minute apex from which a narrow, slightly developed 

 median fold extends out to about the center of the shell, where it becomes elevated and 

 projects forward to the front margin ; the remaining portions of the surface are uniformly 

 convex, sloping away from the median fold to the margin of the valves" (Walcott 

 1923). 



In our collection, an internal mold of the ventral valve was discovered. I add to 

 the original description the following: 



Othoid form, moderately convex, with a strong median sinus which occupies 

 about one third the width of the valve at the anterior mai'gin ; the sides of the median 

 sinus are elevated, and with the downward sloping lateral slopes form a strong, rounded 

 ridge on each side of the sinus. 



Spondylium free not supported by median septum and marked by subparallel 

 ridges, merging into the median sinus. Hinge line long forming about the greatest width 

 of the shell; postero-cardinal angles angular. 



Surface anteriorly marked by a few indistinct strong lines of growth and especial- 

 ly characterized by radiating striae on both lateral slopes. 



Measurements : Ventral valve Interior of ventral valve 



Length 4.0 mm 6.5 mm. 



Width 5.3 mm 7.6 mm. 



Horizon and Loc.\lity: — From the Kaolishan limestone of Tai-An-Fu. (Coll. Y, 

 0. Sun). 



class TRILOBITA Walcott 



Genus AGNOSTUS, Brongniart 



Agnostus cyclopygeformis Sun (sp. no v.) 



Plate II, Figs. la-b. 



Cephalic shield moderately convex, width and length subequal, semicircular in 

 outline and slightly contracted at the postero-lateral angles; rim narrow with uniform 



