1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 443 



has described numerous mammalian forms from the Red Rock Canon 

 section as representing the Ricardo fauna, 15 Ricardo beds, or Ricardo 

 Pliocene. In a recent article 10 the name Ricardo formation was used 

 for the stratigraphic unit containing the fauna of the beds at Ricardo 

 Post Office. 



In some respects there may be justification for use of the name 

 Red Rock Canon beds, formation, or group for the stratigraphic 

 sequence containing the fauna at Ricardo, as this was the first 

 designation used for the section. The name was however not used 

 for nomenclature purposes either by Gilbert or by Fairbanks, and 

 has the disadvantage of extreme length, including as it does three 

 words. The term Mohave formation occurring in Smith's article is 

 again evidently not applied for naming purposes, as it is merely a 

 heading for a division of the paper, with other names a considerable 

 proportion of which are not actually formations. The application of 

 the name is not clear, as it may be presumed to refer to Eocene beds, 

 and an Eocene formation distinct from the Ricardo group is possibly 

 present in the Black Mountain region. Use of the name Mohave, 

 if it were now adequately defined, would certainly lead to confusion 

 of the fauna at Red Rock Canon with the Barstow fauna known from 

 the large exposures in the middle of the Mohave Desert. It has 

 therefore seemed necessary to continue use of the name Ricardo for 

 the fauna occurring in the Red Rock Canon section. In the geologic 

 sense the name Ricardo group may be used for the sequence of strata 

 exposed at Ricardo Post Office with its upward and downward exten- 

 sion within the depositional unit. It is not improbable that several 

 formations may ultimately be mapped within the limits of the Ricardo 

 group. The stratigraphic relation of the Ricardo to the Barstow is 

 not determined, as the two are not known to be in contact. Should 

 the two faunas be found to overlap, the stratigraphic units would 

 perhaps be combined, but distinctness of the faunas makes this 

 improbable. 



is Merriam, J. C, Univ. Calif. Publ., Bull. Dept. Geol., vol. 7, p. 285, 1913; 

 vol. 7, p. 436, 1913; vol. 8, p. 276, 1914; vol. 8, p. 285, 1915; vol. 9, p. 5, 1915; 

 vol. 9, p. 54, 1915; vol. 9, pp. 170-171, 1916. 



16 Merriam, J. C, Pop. Sci. Mom, vol. 86, p. 253, March, 1915. 



