212 



somewhat narrower than those on the lateral portion of tlie shell owing to 

 their dichotomous increase. On the dorsal fold the ribs show an inclination 

 to arrange themselves into three groups. Two ribs separating the median 

 sinus of the ventral valve from the lateral portions are extraordinarily broad, 

 and show dichotomy. Corresponding to these two peculiar ribs, there are two 

 especially deep grooves or furrows limiting the two sides of the mesial fold on 

 the dorsal valve. The interspaces in alternation with the ribs are nearly half 

 as wide as the ribs. Lateral ribs are very simple and distinct even in the um- 

 bonal region. These ribs and grooves are traversed by a small number of 

 concentric growth hnes which are not very distinct. Each of the ribs is pro- 

 vided with very fine, concave stride, which are visible only with the aid of a 

 magnifier. 



Dimensions : — 



Length. Width. Thickness. 



20 mm. 22 mm. i 5 mm. 



25 mm.+ 30 mm. 21 mm. 



Locality : — Huang-tu-pu, prov. Hu nan. 

 This was collected there- in association with 

 Athyris roissyi L'Eveille. 

 R]iync]iouclla plcjirodon Phillips. 

 Geological Age : — Lower Carboniferrus (?). 



Athyridae. 

 Athyris, M'Coy. 



Athyris royssii L'Eveille. 

 PL XXIV., Figs. 10-14. 



1857. Athyris Royssi, Davidson (pars): — Monogr. Brit. Carb. Brach., 



p. 84. pi. XVIIL, figs. 8,- 9, II. 

 1862. Athyris Royssii, Davidson: — On some Brachiopoda collected in 



India by A. Fleming, etc. Quart. Jour. Geol. Soc, vol. XVIIL, 



p. 27. pi. I., fig. 6. 



