TKSTUDINID/E. 



457 



\ portion of the rear (rig. 612) of the carapace along, and tor a short distance on each side 

 of, tlu- midline is preserved. It includes the left hinder corner of the hexagonal sixth neural. 

 This is seen to have had a width, across the hinder end, of "4 mm. Behind it is a little more 

 than the left half of the seventh neural. This is broadest in front, and hexagonal, thru having 

 the anterior angles truncated; and with a maximum width ot about 90 mm. The fore-and-aft 

 extent was about 50 mm. It is succeeded by the eighth neural, which has a length of about 

 40 mm. and a width of about 45 mm. Behind this is a fragment ot the first suprapygal. 

 On it are indications of the fourth and fifth vertebral scutes. The exact length and breadth ot 

 these can not be determined. The fourth was 80 mm. wide behind and the width increases 

 forward; while the fifth is 80 mm. broad at its anterior end and expands rapidly backward. 



The thickened marginal portion of the nuchal bone (fig. 611) is among the remains. Its 

 extent along the front is about 105 mm. It is slightly emarginated at the midline, the edge is 

 abruptly rounded and from the front it thickens rapidly backward, until at a distance of 40 mm. 

 from the edge it is 42 mm. There appears to have been a nuchal scute 20 mm. wide. It is 

 quite probable that all the anterior peripherals were thickened and had obtuse edges. Large 

 portions of the peripherals from the axillary notches backward are present. Those behind the 

 inguinal notches are higher than long; subacute at the free borders, nearly vertical, not flaring, 

 except that the second and third on each side of the caudal peripheral flare slightly. The first 

 behind the inguinal buttress is 160 mm. high. Behind this the others descend, until the pygal 

 (fig. 613) is 115 mm. high at its lateral border. They are all about 80 mm. long at their free 



612. 613. 6i3- 



Figs. 612 and 613. TestuJo campester. Portions of rear of carapace of type. X \. 



612- c.p. 8, eighth costal plate of type; fl.7, .8, seventh and eighth neurals; spy, suprapygal. 



613. Pygal and eleventh peripherals, a, section of eleventh peripheral; per. n, eleventh peripheral; py t pygal. 



borders. The pygal is notcht at its upper border for the second suprapygal, 95 mm. wide at 

 this border, and 65 mm. wide at the tree border. The thickness of the peripherals is about 40 

 mm.; where they articulate with the costals and the pygal the thickness is about 15 mm. The 

 free border of the peripherals is very slightly notcht where it is crost by the sulcus. 



It is proper to compare this species with others which have been described from the Plio- 

 cene deposits. 



T. crassiscutata (Leidy, Trans. Wagner Free Inst., 11, 1899, p. 31, plate vi) differs in having 

 the plastron much broader at its hinder end and with a much wider and shallower notch. The 

 lip of the anterior lobe is also different. 



T. hexagonata Cope, of the Equus beds of Texas (4th Ann. Rep. Geol. Surv. Texas, 1893, 

 p. J"/, plate xxii, fig. 2) has both anterior and posterior lobes of the plastron quite different. 

 Especially is it stated that the sulci defining the pectoral scutes in front and behind approach 

 each other at the midline. In T. campester these sutures are far apart at the midline. 



T. laticaudata Cope, of the Equus beds of Texas (op. cit., p. 75, plate xxii, fig. 1), has the 

 anterior lip of the plastron notcht in the middle so as to be doubly convex, and the lower side 

 of the lip has two longitudinal fossas. The posterior lobe, with its notch, is also different, the 

 notch being much wider and much shallower. 



