NO. 1396. CAMBRIAN BRACHIOPODA—WALCOTT. 297 



Formation and locality. — Lower Cambrian, in sandy shales with 

 Olenellus thompsoni, Kutorgina ci.ugidata, and IpJildea lahrado7'ica. 

 One and a half to 2 miles east of Swanton, Vermont. 



SWANTONIA WEEKSI, new species. 



This shell has the g-eneral form of Sioantonla aidupuita^ but the ribs 

 are finer, more numerous, and crossed b}^ line, sharp concentric stria?. 

 Only the exterior of the ventral valv^e appears to ])e represented in the 

 collection made by Mr. F. B. Weeks. 



Formation and locality. — Lower Caml)rian. In an arg-illaceous 

 shale with fragments of Olenellus, Kutorgina ,'<j)mosa., etc. Three 

 miles north of Volcaldi Spring, or 4 miles northwest of Drinkwater 

 mine, Silver Peak Distric^t, Nevada. 



OBOLELLA ASIATICA, new species. 



General form broad, oval, with the ventral valve showing- a tend- 

 ency to become bluntly acuminate. Valves gently convex. Surface 

 of shell marked by concentric, raised lines of growth that form 

 the front edge of narrow lamella? of varying width; the raised lines 

 are highest on their front side, which gives an imbricated appearance 

 to the surface; fine concentric stride occur on the interspaces between 

 the raised lines. Shell strong, calcareous. 



The specimens occur in a compact, bluish-gray oolitic limestone. 

 None of them show the area or interior of the valves. The reference 

 to Obolella is based on the general form and calcareous shell. The 

 shells vary in size from 3 mm. to .5 mm. 



Oholella asiatlca may be compared with young shells of (). cras.m. 

 Its broadl}^ elliptical form and slight convexity distinguish it from 

 other species of the genus. 



It may be that if material is found showing the interior of the valves 

 the generic reference will be changed; but with the data now avail- 

 able the reference is to Obolella. 



The geological horizon is in some doubt as the specimens were 

 found in a block of river drift limestone. The associated fragments 

 of trilobites are two indefinite for determination. Obolella is a Lower 

 Cambrian genus as far as known, and other blocks of river drift lime- 

 stone at the same locality contained fragments of Olefiellu,s., so the 

 reference of the species is made to the Lower Cambrian. 



Formation and locality. — Lower Cambrian. River drift on the Lan 

 Ho River, 1 mile south of Chen Ping Hsien, Southern Shensi, China. 



Collection of Bailey Willis and Eliot T. Blackwelder, Carnegie Insti- 

 tution of Washington, expedition to China. 



