48 BULLETIN 16 4, UNITED STATES NATIONAL MUSEUM 



chwan, central China, but its peculiar ornamentation easily dis- 

 tinguishes it. 



Forination and locality. — Ordovician: Near Huang-pa-yi, Shensi, 

 China. 



Cotypes.—V.^.'^M.. No. 83642. 



Genus PIONODEMA Foerste, 1909 



PIONODENLA. PUNCTOSTRIATA, new species 



Plate 36, Figukes 2-8, 15 



Four pedicle and three brachial valves constitute the material on 

 which this new species is based. 



Desaiption. — Shell subcircular or subelliptical, unequally bicon- 

 vex; hinge line equal to or slightly less than width of shell; car- 

 dinal angles rectangular or obtuse. Pedicle valve strongly convex, 

 swollen; beak rather high, incurved, hinge area rather large. Bra- 

 chial valve gently convex, with very shallow median sinus; beak 

 small, low, inconspicuous; hinge area narrow. Interior of both 

 valves not clearly observed. 



Surface of valves ornamented with numerous ribs, which are very 

 regular, close, filiform, and rounded, increasing by unequal bifurca- 

 tion or by occasional intercalation at one-fourth to one-half their 

 length. Kibs curve back slightly on both sides toward cardinal 

 angles. Kibs, or sometimes interspaces between the ribs, are cov- 

 ered by rows of very beautiful circular superficial punctae. 



The dimensions of two pedicle valves are : Length, 14 and 13 mm ; 

 width, 15 and 14 mm at hinge area. The dimensions of two brachial 

 valves are: Length, 9.5 and 8 mm; width, 11 and about 9.5 mm 

 at hinge area. 



Comparison. — Th^ general shape of the shell is much like that of 

 Pionodema [Dahnanella] subaequata (Conrad) from the Ki-sin- 

 ling limestone, central China, described by Weller, but it is easily 

 distinguished by its peculiar ornamentation and by the beautiful 

 circular superficial punctae. This characteristic ornamentation also 

 serves to distinguish this species from the others of the genus. 



Formation and locality. — Ordovician : Near Huang-pa-yi, Shensi, 

 China. 



(7o^2/^es.— U.S.N.M. No. 83643. 



Genus POLYTOECHIA Hall and Clarke, 1892 

 POLYTOECHIA CHINENSIS, new species 



Plate 34, Figxjbes 13-21 



Four pedicle valves and one brachial valve constitute the material 

 on which this new species is based. 



