568 PROCEEDINGS OF THE XA TIONAL MUSEUM. vol. xxx. 



Formation and locality. — Middle Cambrian, lower portion of oolitic 

 limestone series; 4 miles east of Fang-lan-chon, Shan-si, China. 

 Collected by P^Iiot Blaokwelder. 



Genus DISCINOPSIS Matthew. 



Acrotretaf ]\Iattiie\v, ISSo, Illustnitions of the Fauna of the 8t. John Group, No. 



6, p. 37. 

 Discinopxix (M.\TTiiE\v MS.) Hall and C'lakke, 1892, Pal. New York, VIII, Pt. 



], pp. lOo, 167. 



The orio'inal diagnosis of the genus is as follows: 



''^Di(((/jiosls. — Shell siibeircular in outline. Surfat-e depressed-con- 

 ical, apices excentric, not marginal. Pedicle-valve with the apex trun- 

 cated by a circular foramitial aperture(?). The interior of this valve 

 is characterized by a pair of deep, diverging furrows, passing forward 

 from the beak or internal foraminal opening, in broad curves which 

 converge toward the anterior margin but without meeting. These 

 furrows enclose a thickened and somewhat elevated central area, which, 

 in the subuml)()nal region is apparently free, projecting for a short 

 distance, like a narrow, triangular shelf, beneath wdiich the foramen 

 probably opened. The interior opening of the foramen is, however, 

 not apparent on any of the specimens examined, for, as usuall}" pre- 

 served, the matrix has adhered to this sul)apical cavit}^, and in a single 

 example only, is the shelf-like character of the median area distinctly 

 demonstrated. A faint longitudinal ridge passes from the apex of the 

 shelf to the anterior margin, ])ut no other markings are discernible on 

 the interior except faint radiating or slightly undulating, prol)ably 

 vascular lines. 



"The interior of the l)riichial valve, as far as known, shows no other 

 chai'acters than the ladiating lines, which a])})ear to belong to the 

 ornamentation of the outer surfuce. 



" Shell-substance tenuous, apparently corneous. External surface 

 covered with more or less prominent, sometimes lamellose concentric 

 growth-lines, crossed by tine, gently curved, radiating strife which are 

 usually more ])i-ominent when the conccMitric lines are exfoliated. 



"Type, Discinopsis gulielmi Matthew.'' 



DI&CINOPSIS SULCATUS, new species. 



Oraniellaj'f sp. Walcott, 1W05, Pnjo. V. S. Nat. Mu8., XXIX, pp. 4, 6. 



This species is based upon the cast of the interior of a small ventral 

 valve, that in its interior markings closeh' approaches the interior of 

 the ventral valve of D/'.schioj)sl,^ guUelml Matthew." 



The interior cast shows that the ventral valve was subcircular in 

 outline, moderately convex, and with the apex probably perforated 



a Illustrations of the Fauna of the St. John Group, 1885, No. 6, p. 37. 



