292 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii. 



texana in being less convex and in having a shallower ventral sinus, 

 less prominent dorsal fold, and more obscure plications. 



The specific name is given in memory of Elkana Billings. 



Forvmtion and locality. — Upper Cambrian. In lentile of limestone 

 interbedded in silicious shales above the Olenellus shales, 1 mile east 

 of Parker's quarry, Georgia Township, St. Albans County, Vermont. 



SYNTROPHIA NUNDINA, new species. 



Triplesia cafc(/em Walcott, Mong. U. S. Geol. Sur., VIII, 1886, p. 75, pi. ii, 

 figs. 7, 8. 



The nonplicate, convex species that is found in the Lower Ordo- 

 vician of the western United States has usually been referred to 

 CameTella or Triplesia caldfera. It is much like the latter, but dif- 

 fers in being less convex, with apex of valves less pointed and incurved. 



Formation and locality. — Lower Ordovician. Pogonip formation. 

 Spur on ridge extending out southwest from Wood Cave; lower east- 

 ern slope of ridge, east of Hamburg Ridge, facing Secret Canyon 

 road; west side of Goodwin Canyon; base of Pogonip limestone north- 

 east of Adams Hill, Eureka District, Nevada. 



Pinkish colored limestone 80 to 75 feet above Algonkian rocks, 

 Williams Canyon, above Manitou, Colorado. 



SYNTROPHIA ORIENTALIS, new species. 



This species is closely related in form and surface characters to 

 Syntrophia texana and some forms of 8. ahnormis. It differs from 

 them in details of surface ribs. On the dorsal valve there are two or 

 three faintly defined radiating ribs on each side of the median fold, 

 which has obscure ribs upon it. Corresponding ribs occur upon the 

 mesial depression of the ventral valve and the side slopes adjoining the 

 depression. The material representing it is too limited to warrant an 

 identification with an}^ described species. S. orientalis is the trans- 

 Pacific representative of S. texana. 



Formation, and locality. — Upper Cambrian. Lower part of Chao 

 Mi Tien (?) limestone, 2.7 miles southwest of Yen Chuang, Province 

 of Shantung, China. Collected by Eliot Blackwelder and Bailey Wil- 

 lis of the Carnegie Institution Expedition, 1903. 



Syntroj^hia, sp. — Three specimens of a ventral valve, very much like 

 that of S. primordialis Whitfield, occur at the same locality as /S. 

 orientalis. 



SYNTROPHIA PRIMORDIALIS Whitfield. 



Triplesia priynordiaiis WniTFiEhB, Ann. Rep. Geol. Surv., Wisconsin, 1877, p. 51. 

 Triplesia primordialis Whitfield, Geology of Wisconsin, IV, 1882, p. 172, pi. x, figs. 



1, 2. 

 Triplesia primordialis Hall, Pal. New York, YIII, 1892, Pt. 1, p. 271. 

 Syntrophia primordialis Hall and Clarke, Pal. New Y^ork, VIII, 1892, Pt. 2, p. 218. 

 Original description.. — Shell small, measuring less than half an inch in width; trans- 

 versely oval in outline, and (juite ventricose in i>rofile; hinge line straight and about 



