458 University of California Ptiblications in Geology [Vol. 11 



width between the ends represents the stage of specialization seen 

 in Testudo and is more advanced than in the Oligocene Stylemys. 



Peculiarities in the form of the median series of plates appear in 

 the small, anteroposteriorly-short, hexagonal neural five ; in the rela- 

 tively large size of numbers six and seven; in the small, narrow, 

 tetragonal number eight ; and in the contact of the bifid anterior 

 suprapygial with the pygial. The modification in relative size of the 

 fifth and sixth neurals is probably in part responsible for the position 

 of the sulcus between the second and fourth vertebral scutes on the 

 sixth neural instead of on the fifth where it is ordinarily located. 



The distal ends of costals three and five are much narrowed and 

 their proximal ends are in articulation with three neurals. Costals 

 two and four are each in contact with one neural. Costal seven is not 

 in contact with neural eight as costal eight wedges in between it and 

 the narrow anterior end of neural eight. 



The characters of the neurals and costals may be due in part to 

 individual peculiarities, but are probably to a considerable degree 

 diagnostic of the group. They are suggested in part in other Ameri- 

 can Tertiary forms, but do not appear in this combination in any 

 other species. 



The large specimen, no. 21574 (fig. 5a), differs somewhat from the 

 type specimen in form of the anterior neurals, but the differences seem 

 to be within the limits of individual variation. In no. 21574 neural 

 one is wider than in the type specimen, and tends to be hexagonal. 

 The second neural is also wider in the large specimen. Neural three 

 is relatively large compared with the second, but is tetragonal, while 

 number two is octagonal. The third costal in the large specimen is 

 much narower distally than in the type. 



The peripherals on the free anterior and posterior borders of the 

 type specimen have acute margins. On the anterior border they may 

 be slightly flared. The middle of peripheral three is slightly behind 

 the suture between costals one and two. 



The pygial plate is considerably wider on the inner than it is on 

 the peripheral margin. Its inner border comes in contact with the 

 distal posterior ends of the bifid first suprapygial. 



In the large specimen, no. 21574, the characters of the peripherals 

 are essentially similar to those of the type. In specimen 21574 the 

 peripherals forming the bridge are nearly vertical in position, with a 

 moderate lateral angle. The bridge peripherals of the type may be 

 similar to those of no. 21574, but are less satisfactorily preserved. 



