1919] Mcrriam: Tertiary Mammalian Faunas of Mohave Desert 533 



Description op Fauna 

 testudinate remains 



Fragments of the shell of a large tortoise found in the Ricardo 

 beds represent a form approximating the size of the large tortoises of 

 the Barstow fauna. Several fragments of peripheral bones differ 

 from those of Testudo mohavense of the Barstow in that the sulci 

 between the dermal scutes are situated on prominent ridges, whereas 

 in the Barstow form the sulci are sharply impressed and do not follow 

 ridges. 



CARNIVORA 



The Carnivora of the Ricardo are in general quite distinct from 

 those of the Barstow, and are also as a rule more progressive. The 

 two faunas seem to have no forms in common, unless it be one of the 

 canids and possibly one large cat. The genus Tephrocyon which 

 forms an important part of the Barstow fauna is not certainly known 

 in the Ricardo. 



The Candidae are represented by a considerable variety of forms. 

 These include a very small species like Canis? infer; an Aelurodon- 

 like form near A. wheelerianus, but with heavier carnassial ; a second 

 Aelurodon-like type near A. wheelerianus, but with different propor- 

 tions of the mandible ; a third very large Aelurodon-like form witli 

 massive molars ; and species which may represent Tephrocyon or small 

 Aelurodons. 



The cats include at least three types, one a machaerodont of the 

 new generic group Ischyrosmilus; the other two forms are imperfectly 

 known. 



A new mustelid constitutes the only other known carnivore of this 

 fauna. 



CANID, small, near CANIS? VAFER Leidy 



Specimen no. 22319 (figs. 138a, 1386) from locality 2731 in the 

 lower portion of the Ricardo represents a small slender-jawed dog not 

 unlike Canis? vafer Leidy of the Fort Niobrara formation, and repre- 

 sented by a similar type in the Snake Creek Pliocene of Nebraska. 



The jaw is slender and the premolar teeth are fairly spaced. The 

 lower canines are long and slender, the premolars are narrow. P„ has 

 a minute posterior basal tubercle. P 4 has a high, sharp principal cusp, 

 with a prominent posterior cusp, a well developed basal tubercle or 



