242 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvni. 



BILLINGSELLA PUMPELLYI, new species. 



General outline subsemicircnlar, greatest width at the hinge line or 

 a little in advance of it; considerable variation exists in the relative 

 proportions of length and width; a ventral valve 8 nun. long has a 

 width of 9 mm.; the dorsal valve is more transverse, length 5.5 mm., 

 width 8 mm. The ventral valve is strongly convex with the umbo 

 arching over to the apex, which is a little above the plane of the mar- 

 gins of the valve; a very slight median fold occurs near the front mar- 

 gin; dorsal valve slightly convex and with a shallow median sinus. 



The surface is marked by low, sharp ribs with wide interspaces, on 

 which fine radiating stria) occur. Concentric lines and stripe of growth 

 cross the radiating striw and ribs. 



The characters of the cardinal areas of the valves are almost 

 unknown; that of the ventral valve appears to have been of moderate 

 height and inclined but a little from the plane of the valve; one inte- 

 rior of the dorsal valve shows a low cardinal process. The cast of the 

 interior of the ventral valve shows the presence of a tripartite elevated 

 umbonal space into which the strong main vascular siiuises extend, as 

 in BhllingtieUa, coloradoensls,' the sinuses extend forward nearly to the 

 front margin of the valve. Of the interior of the dorsal valve only 

 the presence of a strong median ridge is known. 



Ohservations. —This, species is one of the costate forms of the type 

 of B. coloradoensis and B. Tomingeri. It differs fi'om them in surface 

 characters. It may be considered the trans-Pacitic representative of 

 B. coloradoensls. 



The specific name is given in recognition of the work of Raphael 

 Pumpelly upon the geology of China. 



Format km and locality. — Middle Cambrian. Chao Mi Tien lime- 

 stone. Three miles southwest of Yen Chuang, also Chao Mi Tien, 

 Shantung, China. Collected by Eliot Blackwelder and Bailey Willis, 

 of the Carnegie Institution Expedition, 1903. 



BILLINGSELLA RICHTHOFENI, new species. 



This species is represented by two specimens of the exterior of the 

 ventral valve. They vary from 4 to 5 mm. in length and width, the 

 length and width being about the same. The outer surface is marked 

 by fine, obscure, radiating ribs and very fine concentric stria;. The 

 general form is much like that of the ventral valve of BiU Ingsella 

 pumpellyL It difi'ers from the latter in having a shorter hinge line 

 in proportion to the width, the more uniform and stronger convexity 

 of the surface, and the more elevated apex. 



The species is named after Dr. Ferdinand von Richthofen. 



