67 



The hinge-line is straight and the beaks of neither of the valves overhang it. 

 There seems to have been a pretty large area under the beak of the ventral 

 valve, although it is not clear now, because of its having had the beak broken 

 away. The beak of the dorsal valve is far less prominent, and consequently 

 has a very low area. The anterior margin of the shell fluctuates slightly in 

 correspondence with the very slight sinual depression of the ventral valve. 

 The whole surface of the two valves is ornamented with fine radial striae 

 that increase in number anteriorly by means of division or dichotomy. 

 They are separated from each other by spaces of about the same width as the 

 striae themselves. About four of the stria; occupy a space of 2 mm. along the 

 anterior border. Beside these radial thread-like strise there are concentric 

 larger ones that are especialy eminent in the marginal portion of the shell. 

 They look like concentric but somewhat irregular ridges. 

 Dimensions : — 



Length. Width. Thickness. Hinge-line. 



ca, 32 mm. 35 mm. 20 mm. 26 mm. 



Remarks : — In general outline this fossil resembles the Gotlandian form 

 Orthis rustica Sow.'^ But the latter possesses coarse concentic ribs on the 

 surface of the shell instead of fine striae. Besides, its gibbosity is also inferior 

 to that of the present fossil. The median sinual flattening, too, is much better 

 developed in Orthis rustica than in the Chinese species. 



By having two convex valves, the Chinese brachiopod is easily distin- 

 guished from Orthisifia ascendens Pander,-' which has features resembling 

 the former, but with a slightly concave dorsal valve. 



Localty : — Lo-ling-po near No-lu-ping, Tung-hu-hsien, I-chang-fu, prov. 

 Hu-pei. 



Geological Age : — If this is really an OrtJiisina hcvii/>ronitcs v. BuCH, 

 then it represents the Ordovician age. The specimen was collected by Prof. 

 K. Yamada in association with Triplecia poloi and Plectambonites cfr. sericeus. 



1) Davidpon :— Monogr. Brit. Foss. Brach., III., pi. XXXIV., figs. 13-22. 



2) Davidson:— Monogr. Brit. Foss. Brach., V., pi. XVI., figs. 16-18, 



