406 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Daonella duhia is common in the Daonella beds, upper 

 part of the Middle Trias, in the West Humboldt Range in 

 Nevada, in Buena Vista, Cottonwood, and American can- 

 yons. It was also found by the Geological Survey of Cali- 

 fornia under J. D. Whitney at New Pass, in the Desatoya 

 Mountains, Nevada. 



The figured specimens came from the divide between 

 Troy Canyon and the south fork of American Canyon, 

 West Humboldt Range, associated with Beyrichites rotelli- 

 formis, Anolcites meeki, A. ivhitneyi, Ceratites nevadatius, 

 Gymnotoceras blaket, Sagecey-as gahbi, Celt it es halU, and 

 many other forms characteristic of the Middle Trias. 



Genus Pseudomonotis Beyrich, 



1862. Pseudomonotis, Beyrich, Ueber zwei neue Formengruppen aus der 



Familie der Aviculiden, Zeitschr. Deutsch. Geol. Gesell. Bd. XIV, 



p. 9. 

 1886. Pseudomonotis, Teller, in Mojsisovics, Arktische Triasfaunen, p. 105. 

 1900. Pseudomonotis, Bittner, Ueber Pseudomonotis Telleri, und dessen 



Verwandte, Jahrb. k. k. geol. Reichsanstalt, Wien, Bd. L., 1900, 



PP- 559-592. 

 Type, group of Pseudomonotis ocJiotica Keyserling. 



Inequivalve, inequilateral, form oblique, higher than wide, hinge-line 

 straight and long. Left valve arched, right valve flatter ; ear on both valves 

 distinct, with byssal notch in right valve. Radial ribs, with concentric wrin- 

 kles or striae. 



Beyrich named no type for the genus, but said that the 

 species composing it differed little from Monotis; accord- 

 ingly, Teller and Bittner have reserved Pseudomonotis s. str. 

 for the group of P. ochotica. The genus, in the broader 

 sense, has representative species from Permian through 

 the Mesozoic; but the species of the genus as limited by 

 Teller and Bittner are confined to the Trias, and are espe- 

 cially characteristic of the Upper Trias, Noric stage, in the 

 Arctic- Pacific and the American regions. The group of 

 Pseudomonotis ochotica is found in the Noric horizon in New 

 Caledonia, Japan, New Zealand, Siberia, Alaska, British 

 Columbia, California, Nevada, Peru, and Colombia, with 

 nearly related species in all these places, always above the 

 Karnic stage and near the top of the Trias. 



