173 



valve, but it is not especially striking in the umbonal portion of the valve. 

 The anterior border is concave. 



The surface is covered with quite wide and consequently not very nume- 

 rous radial striae or ribs that are rounded on the top. They increase anterior- 

 ly by means of intercalation. In width the interspaces are nearly equal to 

 the ribs themselves. Concentric growth lines are rather extraordinarily well 

 developed, and in reality are concentric lamellae. The radial ribs are tra- 

 versed by them and look like so many radial series of scales. 4 or 5 ribs are 

 counted in a distance of 5 mm. along the anterior border. 

 Dimensions : 



Length. Width (along auricular expansions). Thickness. Hinge-line. 



22 mm. 30 mm. 13 mm. 23 mm. 



24 » — „ 23 „ 



24 „ 34 „ 18 mm. 24 „ 



Locality : — Ning-chiang, Han-chung-fu, prov. Shen-hsi. 

 Associate fossils are ; 



At7'ypa reticularis var. riclitliofcni 

 „ „ var. dcsquamata 



RhyncJioiiclla parallclcpipcda. 



Geological Age : — Middle Devonian. 



N.B. — The papers consulted are, beside those mentioned in the .synonymy 

 of the preceding varieties, the following. 



HuDLESTON Fossils from the Hindu-Khoosh. Geol Magaz., New 



Ser. Decade IV., vol. IX., p. 49. 1902. 



Maryland Geological Survey, Devonian. 1913. 



H. LoEWE : — Die nordischen Devongeschiebe Deutschlads. Neues 



Jaharb., Beil.-Bd., 35 p. 58. 1913. 



Athyridae. 



Athyris, M'Coy. 

 Athyfis eoneentriea von Buch. sp. 

 PI. XXIII., Figs. 4 and 19. 

 1853. Tercbratiila eoneentriea, Schnur :— ZusammenStellung u. liesch- 

 reibung sammtl. im Uebergangsgeb. d. Eifel vorkommend. Bra- 



