582 University of California Publications in Geology [ VoL - 11 



(fig. 229) with a large but narrow astragalus is apparently Alti- 

 eamelus. No. 22519 (fig. 230) may represent Alticamelus. No. 22518 

 (fig. 232) and no. 22520 (fig. 233) are presumably forms of Pro- 

 camelus. 



BOVIDAE 



MEEYCODUS, near NECATUS Leidy 



A considerable number of parts of jaws, horns, and limb elements 

 representing a Merycodus species near the Barstow form referred 

 to M. necatus have been found at Ricardo. Horns and antlers found 

 in the lower portion of this section are not materially different from 

 those of the Barstow species determined as M. necatus, as is seen in 

 no. 22448 (fig. 235). In no. 22449 (fig. 234) the horn has a longer, 

 more slender shaft or beam. In the Barstow fauna forms with the 

 longer beam grade into those with the shorter, flatter beam of the 

 M. necatus type. 



The jaws and teeth of the Ricardo specimens (figs. 236-245) do 

 not differ greatly from those referred to Merycodus necatus in the 

 Barstow fauna, and evidently represent a species near that form. 



In the Ricardo form the lower molars seem in some cases slightly 

 narrower. In M 3 the posterior lobe may be large showing in some 

 cases an incipient division on the outer side (fig. 242), or it may be 

 relatively small and simple (fig. 241). Some of the specimens with 

 the largest lobes are found low down in the section and below the 

 basalt, while specimens with relatively small lobes are known above 

 the basalt. The premolars may be considerably compressed laterally 

 (fig. 240). The characters mentioned may warrant specific separation 

 from the Barstow species when the form is better known. 



In the milk dentition Dm 4 (fig. 239) has a large anterior lobe. 



A number of limb elements (figs. 246-252) of Merycodus found 

 in the Ricardo have not as yet shown characters distinguishing them 

 clearly from the Barstow form. 



The Ricardo form of Merycodus in some respect approaches Capro- 

 meryx of the Pleistocene a little more closely than the Barstow species. 

 The tendency to grooving or division of the third lobe of M 3 is a 

 progressive character. The degree of hypsodonty of the Ricardo 

 species is still much less than in Capromeryx, but the difference sep- 

 arating the two is not more than would be expected in an ancestor 

 of Caprameryx as far removed in time as the Ricardo species is re- 

 moved from that of Rancho La Brea. 



