EVOLUTION OF EARLY PALEOZOIC FAUNAS 107 
feet of the Waucoba Springs section and the Barrel Spring section 
south of Silver Peak in western Nevada! the fauna includes: 
Annelid trails 
Protopharetra, sp. undt. 
Archaeocyathus, sp. undt. 
Ethmophyllum cf. whitneyi Meek? 
Mickwitzia occidens Walcott3 
Trematobolus excelsis Walcott+ 
Obolella, sp. undt. 
Orthotheca, sp. undt. 
Holmia rowei, new species 
Holmia weeksi, new species 
Although this fauna, according to our present knowledge, is the 
oldest known Cambrian fauna, it includes representatives of the 
several classes of invertebrates which I will enumerate. 
Actinozoa.—The corals are represented by a very primitive form 
of Protopharetra, a small form of cup-shaped Archaeocyathus, and a 
small Ethmophyllum closely allied if not identical with Ethmophyllum 
whitneyt (Meek),5 which occurs higher in the section. The latter is 
not a notably simple or primitive form of the Archaeocyathinae; on 
the contrary, it is nearly as far advanced as any species known in the 
Cambrian. 
Vermes.—The annelid borings and trails that occur in and on the 
sandstones and shales are much like those of the Middle and Upper 
Cambrian. 
Molluscoidea.—The two species of brachiopods represent widely 
separated genera. Muickwitzia occidens Walcott® is one of the primi- 
tive forms of the Paterinidae, while Tvematobolus excelsis Walcott? is 
a typical form of the Siphonotretidae. The interval represented by the 
relative development of Mickwitzia and Trematobolus is sufficient to 
convince us that we must look far back in Cambrian, or it may be pre- 
Cambrian, time for the progenitors of the inarticulate brachiopods. 
t Walcott, Smithsonian Miscellaneous Collections, Vol. LILI, No. 5, 1908, 
pp. 185-89. 
2 See Bul!. U.S. Geol. Survey, No. 30, 1886, pp. 81-84. 
3 Smithsonian Miscellaneous Collections, Vol. LIII, No. 3, 1908, p. 143. 
4 Ibid., p. 146. 
5 E. gracile is considered to be a synonym of E. whitneyi (Bull. U. S. Geol. Survey, 
No. 30, 1886, pp. 81-84). 
6 Smithsonian Miscellaneous Collections, Vol. LIII, No. 3, 1908, p. 143. 
7 [bid., p. 146. 
