NO. 10 CAMBRIAN FOSSILS, 4TH CONTRIBUTION RESSER g 



Lingulepis nevadensis, n. sp. 



Liitf/ulclla (Lingulepis) acuminata Walcott (part), U. S. Geol. Surv. Mon. 

 51, p. 545, pi. 34, figs. 3, 3e, 1912. 



This brachiopod is associated with Lingulella tnrneri and evidently 

 formed the basis on which Walcott referred both species to 

 L. acitiiiinata. 



L. nevadensis is characterized by its relatively small size. Both 

 figures of Walcott represent ventral valves, which show the usual 

 degree of variation. The shell is not restricted toward the apex to 

 any great extent. The growth lines are wavy. 



Upper Cambrian, Emigrant; (loc. yz) about 2| miles southeast of 

 Benders Pass, Silver Peak Range, Nevada. 



Cotypcs.—\].S.^M. no. 51884. 



ACROTRETIDAE Schuchert 

 ACROTHELE Linnarsson, 1876 



Acrothele walcotti, n. sp. 



Acrothcic coUcni Walcott (part), U. S. Geol. Surv. Mon. 51, p. 640, text 

 fig- 55. 1912; Smithsonian Misc. Coll., vol. 67, no. 2, p. 25, pi. 4, figs. 5-5C, 

 1917. 



This species is characterized by the coarseness of both the ribs 

 and the growth lines. The outline of both valves is more transverse 

 than in A. coUeni, from which A. tvalcotti further differs in the 

 coarseness of the surface markings. 



Middle Cambrian, Ross Lake shale; (loc. 35c) i mile east of 

 Hector, Mount Bosworth ; and (loc. 63 j) Popes Peak, i^ miles south- 

 west of Stephen, British Columbia. 



Holotypc and paratypcs. — U.S.N.M. no. 51410. 



ACROTRETA Kutorga, 1848 



Acrotreta aurumensis, n. sp. 



Acrotrcta uiicroscopica Walcott (part), U. S. Geol. Surv. Mon. 51, p. 693, 



pi. 67, figs. 2-2d, 191 2. 



Walcott recognized the distinctness of the Nevada species from 

 A. mieroscopica but argued that the different shape was due to pres- 

 sure. Neither the Texas nor the Nevada specimens are compressed 

 or distorted. A. aunnneusis has a more elevated ventral valve and is 

 larger than A. mieroscopica. There is not as much variation in shape 

 as is shown in the illustrations. In fact figure 2a is erroneously 

 drawn, for that shell has the same outline as fig. 2. 



