168 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



ening of the entire surface. The plastron as a whole is large. The 

 total length is 440 mm. The anterior lobe has a length of 117 mm 

 and a breadth at its base of 150 mm. From the base the lateral 

 borders run forward and inward, tunnng inward rather abruptly 

 immediately preceding the junction of the gular-humeral scutes to 

 form a slight notch, as shown in figure 8. The end of the plastron 

 is truncated and is about even Avitli the anterior border of the 

 carapace. 



The posterior lobe has a length of 120 mm and a width at the 

 base of 155 mm, and ends forward of the posterior border of the 

 carapace. The posterior end is angularly concave. The bridge has 

 a width of about 205 mm. 



Gular scutes are present, but I find no trace of intergulars. The 

 gulars measure 3'5 mm in length on the mid line; the humerals 73 

 mm; the pectorals 106 mm; the abdominals 73 mm; the femorals 

 95 mm ; and the anals about 60 mm. 



On the bridge there are indications of four large inframarginals 

 lying principally on the plastron bones. 



As mentioned previously, the ornate sculpture of Baena oi'iiata 

 at once distinguishes this species from all described forms, with the 

 possible exception of B. nodosa. From that species it may be dis- 

 tinguished by the more quadrangular form of the shell; greatest 

 transverse diameter at mid length ; quadrangular shape of first 

 vertebral and the absence of accessory scutes lateral to the first 

 vertebral; and in having all the vertebrals wider than long. 



A second specimen (U.S.N.M. no. 11083) is also identified as 

 belonging to this species. It is larger than the type specimen, 

 and the plane surface of the plastron points to its being a female. 

 This specimen was collected by C. H. Sternberg from the Kirtland 

 formation in the " wash south of Ojo Alamo Wash," 9 miles north- 

 east of Tsaya, San Juan County, N. Mex., in 1923. 



The carapace except in front lacks most of its outer rim, but the 

 plastron is complete except for a small portion of the posterior lobe. 

 It has an estimated length of about 510 mm, which indicates the 

 much larger size of this individual, as the plastron of the type 

 measures only 440 mm. The anterior lobe is strongly notched at 

 the junction of the gular-humeral scutes, as in the type. At this 

 point it has a greatest transverse diameter of 93 mm. The lobe is 

 125 mm long and 183 mm wide at the base. The bridge is 245 mm 

 wide. The posterior lobe is 195 m,m wide at the base. 



A third specimen (U.S.N.M. no. 12821) may also be clearly re- 

 ferred to this species. It was collected by me in SWiy4, T. 24 N., 

 R. 13 W., 3 miles northeast of Hunter's Store, San Juan County, 

 N. Mex., in 1929. 



