-44 



fectly ; thin-walled in the axial part, but much thickened in the peripheral zone 

 where the interspaces are provided with numerous strong acanthopores and 

 occasionally with small mesopores ; almost circular in cross section, having 

 some blunt projections from the wall. Zooecial apertures always oblique to the 

 surface, and arranged in oblique rows. Tabulae rare, especially in the axial 

 part. 



The genus Bntostomclla is common in Upper Palaeozoic rocks, and its 

 oldest representative is hitherto known from the Gotlandian ; as the present 

 species was found b\- Noda in the upper part of his Ping-shan limestone, which 

 is surely of the Ordovician age it is the oldest known form of this genus ; 

 hence the specific name antiqiia is proposed for it. 



Locality : — Huan-chia-chang, Tung-hu-hsien, prov. Hu-pei. 



Gastropoda . 

 Raphistomidae. 



Maclurea, Leseur. 



Maclurea neritoid.es Eichwald 



PI. XVI., Fig. i2a.-b. 



i86o. Machirea neritoides F^ichward : Lethaea Rossica, p. 1140, pi. 

 XLIIL, fig. 14. 



1897. neritoides Koken : Die Ga.stropoden des baltischen Unter- 

 silurs, p. 147. 



191 1. M. neritoides Frech : in Richthofen's China vol. v, p. 10, pi. IV., 

 figs. la-2b. 



Sinistral shell with flat spire and somewhat convex and widely um- 

 bilicated base ; whorls 3 or 4, rapidly enlarging ; outer edge of the whorls 

 obtusely angular ; outer side slightly convex ; umbilicus wide and abrupt, ex- 

 posing about half of the inner whorls. 



