80 RESEARCH IN CHINA. 



with the umbo arching over to the apex, which is a little above the plane of the 

 margins of the valve ; a very slight median fold occurs near the front margin ; 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 strias occur. Concentric lines and striae of growth cross the radiating 

 striae 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 a.nd inclined but a 

 little from the plane of the valve ; one interior of the dorsal valve shows a low cardi- 

 nal 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 sinuses 

 extend, as in Billingsella coloradoensis (Shumard) [Walcott, 19126, plate LXXXV, figs. 

 i, ia-z]; the sinuses extend forward nearly to the front margin of the valve. On 

 the interior of the dorsal valve only the presence of a strong median ridge is known. 



This species is one of the costate forms of the type of B. coloradoensis (Shumard) 

 and B. romingeri (Barrande) [Walcott, 19126, plate xc, figs. 2, 20-11}. It differs from 

 them in surface characters. It may be considered the trans Pacific representative 

 of B. coloradoensis. 



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

 upon the geology of China. 



Formation and Locality. Upper Cambrian: (C61) A dense black limestone 

 in the uppermost limestone member of the Kiu-lung group [Blackwelder, 19070, 

 pp. 37 and 41 (third list of fossils), and fig. 10 (bed 13), p. 38], 3 miles (4.8 km.) 

 southwest of Yen-chuang, Shan-tung; also (C36) upper part of the Ch'au-mi-tien 

 limestone [idem, p. 36 (part of third list of fossils), and fig. 9 (bed 2), p. 35], at Ch'au- 

 mi-tien, Ch'ang-hia district, Shan-tung, China. 



This species is somewhat doubtfully identified from Lower Cambrian, (C20) 

 central part of the Man-to shale formation [Blackwelder, 19070, p. 26 (last list of 

 fossils), and fig. 6 (bed 14), p. 25], on the west side of an isolated butte i mile (1.6 

 km.) south of Ch'ang-hia, Shan-tung, China. 



The first collected by Li San; the second and third by Eliot Blackwelder. 



Billingsella richthofeni Walcott. 

 Plate 4, Figure 5. 



Billingsella richthofeni WALCOTT, 1905, Proc. U.S.Nat. Mus., vol. xxvm, p. 242. (Characterized and 



discussed as below as a new species.) 

 Billingsella richthofeni WALCOTT, 1912, Monogr. U.S. Geol. Survey, vol. LI, pp. 761-762, plate LXXXIX, 



fig. i. (Copy of the preceding reference.) 



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 striae. The general form is much like that of the 

 ventral valve of Billingsella pmnpellyi [p. 79]. It differs from the latter in having 

 a shorter hinge-line in proportion to the width, in the stronger and more nearly 

 uniform convexity of the surface, and the more elevated apex. 



The species is named after Dr. Ferdinand von Richthofen. 



Formation and Locality. Lower Cambrian: (C3) Lower part of the Man-t'o 

 shale formation [Blackwelder, 19070, p. 28 (list of fossils at bottom of page), and 

 fig. 8a (bed 20), p. 28], on the southeast slope of Hu-lu-shan, 2.5 miles (4 km.) 

 southwest of Yen-chuang, Sin-t'ai district, Shan-tung, China. 



