NO. 1395. CAMBRIAN BRArillOPODA—WALCOTT. 239 



Doctor Linnarsson gives a fine series of illustrations of the interior 

 of the ventral valve, which shows that there is considerable variation 

 in the position of tlic vascular markings. He states that the small 

 cardinal process appears to be bifid. 1 find it single in a natural cast 

 in the limestone from Alunbruk. There is also a narrow median sep- 

 tum as in the dorsal valve of B. coloradoensis. 



Doctor Linnarsson writes: 



I do not know any species witli which this can be confonnded. At. least the aduh. 

 specimens are always easily recognized. In the young ones the characters are less 

 marked, especially in the dorsal valves. The interior and the internal cast of the 

 ventral valve is in all stages of growth easily recognized. 



Formation and locality. — Middle Cambrian. Zone of Paradoxides 

 forchhamineri. Kinnekulle and Lovened in Westrogothia, Island of 

 Oland, at Sodra Mocklebv and Alanbruk, Sweden. Doctor Linnars- 

 son also found it in loose stones at Lillviken Jemtland. The speci- 

 mens I have illustrated were collected by M. Schmalensee at Alanbruk. 



BILLINGSELLA MAJOR, new species. 



In general form andconvcxit}- this shell is related to B. coloradoensis. 

 It differs from it in being larger and in having coarser radiating ribs. 

 It is the Upper Caml)rian representative of the latter species. 



FoTinatlon and locality. — Upper Cambrian. Fine grained, l)uli' 

 colored sandstone in excavation on Wells' farm, 2 miles west of Bar- 

 aboo, Wisconsin. 



BILLINGSELLA OBSCURA. new species. 



This species is founded on a single dorsal valve that occurs in the 

 form of a cast in sandstone. It is transverse, width 18 mm., height 

 13 mm. ; moderately convex with a slightly defined mesial flattening 

 that broadens out nearly to three-fifths the width of the shell at the 

 front margin. The surface of the cast is marked by a few faintly 

 defined, rather broad costse. 



The shell is much like the large dorsal valves of B. cohyradoensh. 

 It differs in its broader frontal margin and median flattening. 



Forniation and locality. — Middle Cambrian. Thin bedded sand- 

 stones just above the massive Tonto sandstone near the head of Nun- 

 koweap Valley, Grand Canyon of the Colorado, Arizona. 



BILLINGSELLA ORIENTALIS Whitfield. 



Ch'thisina orientalis Whitfield, Bull. Amer. Mus. Nat. Hist., I. 1884, p. 144, 



pi. XIV, tig. 6. 



Orthisina orientalis Walcott, Bull. U. S. Geol. Sur.. No. 30, 1886, p. 120, 



pi. VII, fig. 6; Tenth Ann. Rept. U. S. Geol. Sur., 1891, p. 613, pi. lxxii, fig. 8. 



BillingseUa orientalis Hall and Clarke, Pal. New York, VIII, 1892, Pt. 1, p. 230. 



Original description. — Shell quadrangular in outline, somewhat higher than wide, 



with vertical and subparallel lateral margins and broadly rounded base. Cardinal 



