LOWER CRETACEOUS SERIES. 727 



Near the lowest exposures in Yucca and Bluff mesas and in Malone Moun- 

 tain, very near the upper edge of the siliceous limestone, this conglomerate 

 occurs in a horizon twenty to thirty feet thick. The material composing the 

 conglomerate is pretty well worn limestone and chert pebbles, resembling, in 

 surface appearance, the material of the Etholen breccia. The limestone peb- 

 bles are formed of concentric circles or rings of limestone ranging outward 

 from a nucleus at the centre. 



SECOND CAPROTINA HORIZON. 



This occurs at the top of the Yucca bed, in thickly-bedded to massive lime- 

 stone fifteen feet thick. The fossil is shown in section iD the face of the hard 

 rock. Its hornlike shell structure and its peculiar shape give no doubt of its 

 detection to one who is at all acquainted with the form. 



The Yucca bed occurs in the northeast sides of Yucca, Camp, and Bluff 

 mesas, in Quitman Mountain south of Quitman Pass, and in the whole extent 

 of Malone Mountain. Parts of it also occur in the southwest side of Quitman 

 Mountain, south of Big Spring Gulch, as parts of the beds both above and 

 below are there. 



Igneous action has been so great in Quitman Mountain that the stratified 

 rock in contact with the granite can not be recognized unless they contain 

 very refractory fossils or other evidence outside the common lithological 

 characters of the rock. Yucca beds in Malone Mountain extends a short dis- 

 tance above the pisolitic limestone into the marble flags, as represented in 

 Yucca and Bluff mesas. 



BLUFF BED. 



Bluff and Yucca mesas are the northwestern extension of the line of sim- 

 ilar hills that pass from Eagle Mountain in a northwesterly direction to within 

 two miles of Etholen Station. Near Eagle Mountain these hills are known 

 as Devil's Ridge, while farther to the northwest they are known as Devil's 

 Backbone. The character of the topography is the same throughout; that is, 

 abrupt steep declivities and bluffs facing the basin leading northeastward to 

 the Sierra Diabolos, flat to south westward sloping tops, and sloping to steeply 

 inclined sides, following generally the dip of the rock to the basin on the 

 southwest leading south to the Rio Grande and southwest to the Quitman 

 Mountains. 



The rocks invariably have a southwestward dip. Strikes range from north 

 50° to north 60° west. A glance at the section given under Yucca bed on 

 page 725 will show the succession of the strata of this bed and its connection 

 with the rocks of Yucca bed. 



As was the case with Yucca series, the Bluff series begins with sublittoral 



