456 



University of California Publications in Geology [ VoL - 11 



TESTUDO MOHAVENSE, n. sp. 



Type specimen no. 21575, carapace nearly complete, plastron complete (figs. 

 4a, 4& ) ; from the Barstow beds, Barstow syncline, Mohave Desert. Two indi- 

 viduals, nos. 21573 and 21574, much larger than the type specimen, but resembling 

 it in general structure, are tentatively referred to this species. 



The characters of this, species approximate those of a group of 

 Miocene species referred to the genus Testudo though the assemblage 

 of characters does not correspond to that in any of the known forms. 

 In some respects, as in the nature of the epiplastral lip, it resembles 

 the West American Oligocene genus Stylemys, but shows clearly a 

 more advanced stage, which is comparable to that of Testudo. 



The carapace of the type specimen is 232 mm. long with a width 

 of 196 mm. The plastron of the type is 222 mm. long. The more 

 nearly complete of the two large specimens referred to this species 

 is 317 mm. wide and the plastron is approximately 375 mm. long. 

 The carapace of the type (fig. 4a) is truncated or concave anteriorly. 

 It is seen to be moderately arched in the type specimen, but distortion 

 of the shell has made exact estimation of the form difficult. In the 

 larger specimens the vault of the carapace is strongly arched. The 

 plastron (fig. 45) is strongly notched posteriorly. The epiplastral 

 lip is strongly developed superiorly, but is not clearly set off from 

 the contour of the posterior portion of the anterior lobe of the plas- 

 tron. The separation of the epiplastral lip is not more distinct than 

 in Stylemys and not less marked than in certain Miocene species of 

 Testudo, as in Testudo pansa. The anterior lobe of the plastron 

 projects slightly beyond the anterior end of the carapace. The bridge 

 between the plastron and carapace extends from the anterior portion 

 of the second costal to the anterior end of the sixth costal. The form 

 and arrangement of the neural and costal plates are in general as in 

 the Testudo group. Neurals two and four are octagonal, three is 

 tetragonal, five is hexagonal. Neurals three and five are both rela- 

 tively small. Neurals six and seven are both hexagonal and of nearly 

 the same size, number seven being slightly longer anteroposteriorly. 

 Neural eight is relatively very small and tetragonal. The anterior 

 suprapygial is bifurcated, the posterior wings enclosing the cuneiform 

 second suprapygial, and coming into contact with the lateral borders 

 of the pygial. 



The costals from the second to the seventh show much variation 

 between the width of the lateral and median ends. The variation in 



