FOSSIL TURTLES OF NORTH AMERICA. 



downward; whereas, the border of the second peripheral is turned upward. It is probable 

 that the bone is an intrusion from another species. 



The sulci of the plastron are wholly effaced. On the costals they are narrow, but distinct. 

 As seen from plate 37, fig. 7, the sulci limiting the vertebral scutes laterally are not far removed 

 from the costo-neural sutures. The first vertebral was evidently wider than those succeeding 

 it. If the neurals had the relative width that they have in Adocus punctatus, the third vertebral 

 must have been 52 mm. wide. On the second and third peripherals the longitudinal sulci 

 lie not far above the free border of the carapace. The sulci on the supposed eighth and ninth 

 peripherals are so obscure that they can not be traced. 



Agomphus tardus Wieland. 



Text-figs. 314-318. 

 Agomphus tardus, WIELAND, Amer. Jour. Sci. (4), XX, 1905, p. 430, figs. 1-7. 



This species was found in the Cretaceous marl pits at Birmingham, Burlington County, 

 New Jersey, in 1869. The type forms number 774 of the Marsh collection at Yale University. 

 The parts recovered are most of the nuchal, the second and the fifth neurals, the first and 

 second left costals; fragments of the third and fifth, and the whole of the eighth right costals; 

 of the right peripherals, the first, eighth, ninth, and tenth; of the left side the fifth, sixth, tenth, 

 and the eleventh; the left hyoplastron, and the right hypoplastron. These parts have enabled 



epi 



per. 11 



FlGS. 314 AND 315. Agomphus tardus. 



xiph 

 Carapace of type. 



314. Sections at anterior ends of peripherals indicated by the numerals. Xj. c, in first peripheral, pit for pro- 



cess of nuchal, s, in eighth peripheral, sutural border for union with hypoplastron; py, section of pygal. 



315. Shell seen from left side. Xo.23 c.p. i, etc., costal plates; />;', epiplastron; hyo, hyoplastron; hypo, hypo- 



plastron; nu.pj nuchal plate; per. i, per. ^, etc., peripheral bones; xiph, xiphiplastron. 



Dr. Wieland to restore satisfactorily the form of the shell. A number of his figures are here 

 reproduced. 



The bones of this species were even thicker and heavier than in A. petrosus. The shell 

 (figs. 314-318) was elongated and rather high. From the highest point the carapace sloped 

 gently to the front, while the rear sloped rapidly downward. The length of the carapace was 

 about 330 mm.; the greatest breadth, about 230 mm. The nuchal bone is 53 mm. long and 

 52 mm. wide along the free margin. It is 13 mm. thick near the free margin and 7 mm. thick 

 posteriorly. The second neural has a length of 40 mm., an extreme width of 35 mm., and a 

 thickness of 14 mm. The fifth neural is 40 mm. long, 36 mm. wide, and 15 mm. thick. As 

 in A. petrosus, the first costal attains considerable thickness at the junction with the second 

 and third peripherals, being here 22 mm. thick. The rib-heads are diminutive. All the 

 peripherals are very obtuse at their free borders. Fig. 314 shows the form of the anterior end 

 of the first, the second, the eighth, the ninth, the tenth, and the eleventh peripherals, as well 

 as of the border of the pygal that joins the eleventh peripheral. It will be observed that the 

 thickness of the first and the second near the middle of the height is maintained to the costal 

 border. 



The nuchal scute is moderately broad. The sulci bounding the vertebrals and the costals 

 have not been observed. The costo-marginal sulci run along on the upper half of the periph- 

 erals, without at any time reaching the costal bones. 



