183 



Localities : — Pcr.-chao-tze, Chao-hua-]isien, Pao-ning-fu, pi'ov. Sze-cliuan ; 

 Ning-clu'ang, Ilan-cliiing-fu, prov. Shen-hsi. 



In the second localty several other brachiopods were discovered, of 

 wliich tlie following determine the geological age of the rock that 3^ielded 

 them. 



/it)ypa TLtiiiilai is var. J-i Si/iiaiiiatit 

 var. I irlttliufcni 

 ]\liyihli(>ihlla f^tualUli f^if^iila. 



From these associate fossils it seems that the present fossil is of the 

 jNIiddle Devonian. As this fossil was collected in association with the type 

 species described just above, the latter also is a fossil indicative of the Middle 

 Devonian Age. 



Geo'ogical Age ; — Middle Devonian. 



Athyrisina minor n i\ . sp. 



ri. XXIIJ., Figs. ,S-I2. 



Shell small and somewhat circular in outline, and more or less strongly 

 biconve.x, ventral valve being usually more gibbous than the opposite one. 

 Hinge-line ver}' short and curved. Ventral valve uniformly curved in the longi- 

 tudinal direction, but the dorsal waive is most c<invex in the visceral region, a 

 little in front of the beak ; on the whole; it is rather tlatter than the other. 

 Ventral beak more or less acuteh" projecting and strongh' recurved ; its end is 

 obliquel}- truncated by a circular pedicle hole. There is no visible cardinal 

 area beneath the ventral beak. Median sinus is already developed in the 

 beak region, but first becomes distinct in the visceral part. It rises almost 

 verticalh- at the anterior margin, (|uite suddenly becomes deeper and wider 

 anterior!)-, and ends in an angular prolongation at the front margin. Dorsal 

 beak not prominent, but hidden beneath the opposite beak. Median fold de- 

 veloped only on the anterior half of the shell, rising very abruptly above the 

 level of the lateral porlion of the shell. The margin forms a zigzag, owing 

 to the angular and high radial ribs on each side of the shell, that are separated 



