656 CAMBRIAN BRACHIOPODA. 



think that it is probable that the two forms are specifically identical, as the interiors of the 

 valves of several species of Acroihele appear very much alike. 



Formation and locality. — Middle Cambrian: (C57) Limestone nodules in the lower shale member of the 

 Kiulung group [Blackwelder, 1907a, pp. 37 and 40 (first list of fossils)], 3 miles (4.8 km.) south of Kaokiapu and 

 about 4 miles (6.4 km.) north of Sintaihien, Sintai district; and (C23) upper part of thin-bedded gray oolitic lime- 

 stone at the base of the Changhia formation [Blackwelder, 1907a, p. 82 (list of fossils), and fig. 6 (bed 20), p. 25], 50 

 feet below the base of the cliffs 1 mile (1.6 km.) east-southeast of Changhia; both in Shantung, China. 



ACEOTHELE SPUEEI Walcott. 

 Plate LX, figures 3, 3a-c. 



Aa-oihele subsidua Walcott (in part) [not White], 1886, Bull. U. S. Geol. Survey No. 30, p. 109, PI. IX, fig. 4 (not figs. 



4a-c). (Locality mentioned in discussion of A. subsidua. The specimen represented by fig. 4 is redrawn in 



this monograph, PL LX, fig. 3. Figs. 4a-c belong with Acrothele subsidua.) 

 Acrothele subsidua Walcott (in part) [not White], 1891, Tenth Ann. Kept. U. S. Geol. Survey, p. 608, PL LXX, fig. 1 



(not figs. la-c). (Mentioned. Fig. 1 is copied from fig. 4 of preceding reference. Figs, la-c belong with 



Acrothele subsidua.) 

 Acrothele subsidua Walcott, Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, p. 103. (Dis- 

 cussed as possible new species.) 

 Acrothele spurri Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 86-87, PL VIII, fig. 14. (Described and 



discussed as below as a new species. Fig. 14 is a revised drawing of the specimen represented by fig. 4 of the 



preceding reference. Fig. 14 is copied in this monograph, PL LX, figs. 3, 3a-b.) 



General form transversely ovate. Ventral valve depressed with an elevated apex a little 

 in front of the posterior margin; from the apex the surface slopes rapidly and then gradually 

 to the front margin, and quite rapidly to the posterior margin; the posterior margin arches 

 up from the plane of the sides of the valves about one-half the height of the apex and gives to the 

 valve the appearance of being pushed up so as to throw the apex toward the front; a minute 

 pedicle opening truncates the apex at its posterior side; a small, subtriangular, convex false 

 area extends from just back of the apex to the posterior margin. 



Surface of the epidermal layer marked by fine, concentric striae of growth and a very 

 minute granulation; the inner laminations of the shell are shiny and marked by numerous 

 radiating striae and a few concentric lines. Shell corneous and built up of numerous layers or 

 lamellae more or less obhque to the outer layer. 



Dorsal valve and interior of valves unknown. The largest ventral valve has a length of 

 6 mm.; width, 7 mm. 



Oiservations. — This very striking species is associated with Acrotreta primseva Walcott and 

 Olenellus gilherti Meek, in the upper portion of the OleneUus zone of central Nevada. Some 

 fragmentary specimens of tliis species were referred by me [18S6b, p. 109] io Acrothele subsidua 

 (White) , but with better material and more thorough study, the Lower Cambrian specimens are 

 referred to A. spurri. A. spurri differs from A. subsidua in the more posterior position of its 

 apex, in its convex, distinctly marked false area; in its strongly arched posterior margia; and 

 in its more finely granulated surface. The convex false area and arched posterior margin are 

 features also seen in A. woodworthi of the Lower Cambrian (PI. LX, fig. 6). 



The specific name is given in honor of Mr. J. E. Spurr. 

 Formation and locality. — Lower Cambrian : (31a) Limestone and interbedded siliceous shales of the Pioche formation 

 [Walcott, 1908a, p. 11], just above the quartzite on ike east side of the anticline, near Pioche, Lincoln County, Nevada. 



Specimens that are somewhat doubtfully referred to Acrothele spurri Walcott occur at the 

 following locality: 



Lower Cambrian: (11) Shales of No. 3 of the Silver Peak group [Walcott, 1908f, p. 189], 2.5 miles (4 km.) south of 

 Barrel Spring and 0.5 mile (0.8 km.) east of the road, in the extreme southeastern corner of the Silver Peak quadrangle 

 (U. S. Geol. Survey), Esmeralda County, Nevada. 



Acrothele stjbsidxta (Wliite). 

 Plate LX, figures 1, la-o, 8. 



Acrotreta? subsidua White, 1874, U. S. Geog. Surveys W. 100th Mer., Prelim. Rept. Invertebrate Fossils, p. 6. 

 (Described as a new species.) 



