304 rBOCEEDINOS OF THE NATIONAL MUSEUM. vol. xxviii. 



from the posterior niarg-iii to the center of the valve; this ridge is 

 anguhir at the summit and broadest toward its anterior end. A vascu- 

 lar sinus starts on each side of the base of the median ridge and 

 extends obli(|ueh' forward. 



The dark interior surface of the valves is marked by concentric lines 

 that give a somewhat laminated appearance to the surface. From the 

 manner in which the shell adheres to the limestone matrix, it is prob- 

 able that its outer surface is roughened hy raised lines, somewhat as 

 on Acrof/u'h' auhsldna. 



The data for comparison of this species with described species from 

 America and Europe are too limited to bo of value. A comparison with 

 Acrothele {inohergid) (jrani(J(d((^ Rodlich, of the Salt Range, India, 

 shows a strong similarity in the interiors of the dorsal valves; but 1 

 do not think it is probable that the two forms arc specitically identical, 

 as the interiors of the valves of several species of Acrothele appear 

 very uuich alike. 



Formation and locality. — Middle Cambrian, Chang Hsia limestone. 

 Three miles south of Kao Chia Pu, Shantung, China. 



Collected by Mr. Eliot Blackwelder, of the Carnegie Institution of 

 Washington, expedition to China. 



IPHIDELLA, new genus. 



Iplddea Billings, Can. Nat., new ser., YI, 1872, j). 477, lig. 13, and of Authors. — 

 Not Iphldea Bayley, 1865. 



For synonomy and description of Iphidea=lphidella, see Proc. U. S. 

 Nat. Mus., XIX. 1897, p. 707. 



IPHIDELLA MAJOR, new species. 



Ventral valve subconical, with the apex slightl}- in front of the 

 posterior margin. A minute beak appears to incurve over the pseu- 

 dodeltidium. Cardinal slope rather abruptly rounded so as to indi- 

 cate a rather narrow area. Pseudodeltidium l)road, convex, with its 

 lower margin arched so as to leave a space between it and the hinge 

 line of the shell. Dorsal valve slightly convex, with a narrow area 

 and broad, apparenth' open delthyrium. 



Surface, as far as can be determined from the badly preserved 

 material, marked by very tine concentric striie. 



The material representing this SY)ecies is more or less compressed 

 and distorted in the argillaceous shales in which it occurs. In general 

 form it is not unlike that of /. lahradorlca, but it differs in its nearly 

 smooth surface and the y^osition of the apex. From /. .^oij^erha it 

 differs in its much greater size, although resembling it in the narrow 

 and perfectly deiined area of the ventral valve, and the large, broad, 

 convex pseudodeltidium. 



Formation and locality. — Lower Cambrian. Argillaceous shales, 4 

 miles south of Helena. Slielbv Countv. Alabama. 



