2l6 



one of the broken specimens, wluch shows the interior of the shell, it is 

 observed that the spirals are directed laterall)'. 

 Dimensions : — 





Width. 



Thiokne-ss. 



Hin-'e-liuo. 



1 3 mm. 



16 mm. 



8 mm. 



1 0 mm. 



14 mm. 



I 7 mm. 



8 mm. 



1 0 mm. 



I 5 mm. 



1 8 mm. 



9 mm. 



1 I mm. 



I 5 mn). 



1 8 mm. 



8.5 mm. 



r I mm. 



I 8 mm. 



20 mm. 



13 mm. 



[4 mm. 



Remarks : — As already stated by Davii'Siix one of the f<^i*ms most closel>' 

 resembling this .species is probably Athyris pla)iosulcata. The concentric 

 growth Unes of the Cliinese specimens are sometimes more or less prominent 

 and then look something like inconspicuous lamelLe. They are, however, by 

 no means equal to the lamell;e that characterize the species just mentioned 

 above. With regard to this point D.widson s notice in his monograph should 

 be consulted. 



^■It/iyn's cx/'niisi7 Piiii.L.^^ also is not fundamentally different from the 

 species just under consideration. This, however, is not so small a species as 

 the latter. Also the ventral beak of the former is quite obtuse and not pointed 

 as in the latter. Moreover, Atliyrb cxpaiisa seems to be somewhat more 

 elongated transversely in outline than .1. rovss//. 



There is another .species which it is necessary to compare with the present, 

 namely, Athyris Dicnibraiiacca 1 )K Kon."^ The small examples of this species 

 too are without sinus or fold on the valves respectively. It has a habitus 

 very similar to that oi Athyris rnyssii of China. L)e Koninck"s species, 

 however, is mucli less transverse in form ; it is also inferior in thickness to 

 Aihyris royssii. Thus the latter species appears to be a for;u between 

 Athyris filaintsitlcati-i and . I. uiiir.brauacca. 



Localit}' : — fluang-tu-pu, nrov. Hu-n;ui. Associate fossils are : 

 Spirifcr bisiilca.tiis. 

 RhyncJioiiilla plcii) odoii. 



1) Phillips: — Geology of Vorkshirt, II., p. 220, 12. -\.. fig. 18. 1S36. 



2) De Kon nck:- op. cit., p. 8g. pi. XL, figs. 1-6. 



