PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 127 
in large Maclurites which are suggestive of those of the Chazy group of the 
Champlain Valley, N. Y. The upper part of the zone is characterized by abun- 
dance of Receptaculites. No brachiopods have been described from this zone. 
Rhysostrophia sp. 1 
Desmorthis zone.—This zone overlies the Receptaculites beds of the Pal- 
laseria (Mitrospira) zone. The bed is well displayed under the Eureka quart- 
zite on the west and south sides of Lone Mountain about 18 miles west-northwest 
of Eureka, Nev. It consists of dark, moderately heavy-bedded limestone con- 
taining Desmorthis nevadensis Ulrich and Cooper in abundance and often ex- 
quisitely silicified. In addition, Anomalorthis nevadensis Ulrich and Cooper 
and A. lonensis (Walcott) occur. Hesperonomiella minor (Walcott) is a less 
well known species. 
Correlation—Abundant Desmorthis and Anomalorthis signify correlation of 
this part of the ““Pogonip” with the Joins formation of Oklahoma. 
Anomalorthis zone.—Under this heading are placed thin-bedded limestones 
abounding in sponges described by Bassler (1941), abundant Pseudomera and 
other peculiar trilobites, together with Anomalorthis and a few other brachiopods, 
as follows: 
Aporthophyla typa Ulrich and Cooper Orthambonites minusculus (Phleger) 
Idiostrophia paucicostata Cooper Porambonites sp. 1 
Lingulella sp. 1 
Correlation.—Presence of the trilobite Pseudomera and the brachiopod Ano- 
malorthis indicate correlation with the Oil Creek formation of Oklahoma. 
Rhysostrophia zone.—Consists of thin-bedded limestone abounding in fos- 
sils. Some of the brachiopods are silicified, while others occur in a silicious 
matrix which permits dissolving the shell away from the rock to produce impres- 
sions of the interior. The following species are known: 
Goniotrema perplexum Ulrich and Cooper Rhysostrophia nevadensis Ulrich and Cooper 
Hesperomena leptellinoidea Cooper R. occidentalis Ulrich and Cooper 
Leptellina occidentalis Ulrich and Cooper Sowerbyella rugosa Ulrich and Cooper 
Orthambonites bifurcatus Cooper Syndielasma biseptatum Cooper 
O. occidentalis Cooper Taphrodonta parallela Cooper 
O. paucicostatus (Ulrich and Cooper) Toquimia kirki Ulrich and Cooper 
Orthidium bellulum Ulrich and Cooper Valcourea intracarinata Ulrich and Cooper 
Porambonites ? umbonatus Cooper 
Correlation.—This is a difficult fauna to place, but it has obvious affinities with 
the Table Head Series of Newfoundland and some of the boulders of the Mystic 
conglomerate. Rhysostrophia occurs in both of the formations named and so 
does Orthidium. The latter genus also links these beds to the limestone No. 2 
of Lévis, Quebec. The Newfoundland faunas are still too little known to make 
any close comparisons. Another genus common to the Table Head and Rhyso- 
strophia zone is Porambonites. 
EuREKA GROUP: Lower 25-foot sandstone.—On Martins Ridge, west side 
of Antelope Valley, northeast of the Martin Ranch, the Pogonip is overlain by 
