TRIONYCHID^E. 



537 



3. Carapace oval, not so wide as long, archt; nuchal about half the width of cara- 



pace; pits of costals small and shallow; hinder end of carapace with longitudinal 



welts trionychoiJes 



4. Carapace as broad as long; nuchal hardly half the width of the carapace; a 



smooth band along its front; sculpture coarse near midline heteroglypta 



5. Carapace broader than long; nuchal more than half the width of carapace; 



pitted to free border; sculpture as in preceding poster a 



6. Carapace broader than long; nuchal not half the width of the carapace; 



sculpture like that of heteroglypta extensa 



A*. Oligocene species: 



I. Carapace thin, broader than long; nuchal 0.6 the width of the carapace; a 



fontanel each side of first neural leucopotomica 



A''. Pliocene and recent species: 



I. Carapace elliptical; longer than wide; nuchal about half the width of the cara- 

 pace; sculpture rather coarse ferox 



Platypeltis antiqua Hay. 

 Fig. 693. 



Platypeltis antiqua, HAY, Bull. Amer. Mus. Nat. 

 Hist., xxiii, 1907, p. 859, fig. 18. 



The specimen which represents this species 

 appears to have been collected for Professor 

 Cope by Mr. D. Baldwin, in 1883, in the 

 Torrejon beds of northern Mexico. It pre- 

 sents wholes or parts of 5 pairs of costals and 

 5 neural bones. Some other bones are buried 

 in the very refractory matrix. The catalog 

 number is 1036. 

 The carapace 

 (fig. 693) had a 

 length of about 

 IOO mm. and a 

 width of 78 mm.; 

 but the ends of 



'-"''' ^'' i A' ""~~~" 

 / > ^ \ 



FIG. 693. Platypeltis antiqua. Carapace 

 of type. X . 



the ribs extended beyond the disk at least 1 8 



mm. What is evidently the first costal is 20 



mm. long, from neural to distal end, and 13 



mm. fore and aft. Its anterior border is smooth, showing that it was not suturally joined to 



the nuchal. The table shows the dimensions of the neurals present. They are from 2.5 mm. 



to 3 mm. thick. 



The surface of the costals presents no welts, but is everywhere pitted. On the proximal 

 ends of the costals there are 6 pits in a 10 mm. line; on the outer ends, 5 pits. 



Platypeltis serialis (Cope). 

 Plate 98, fig. 13; plate 109, figs. 1-4; text-figs 694-696. 



Trionyx, LEIDY, Contrib. Ext. Vert. Fauna West. Terrs., 1873, p. 180, plate xvi, fig. n. 



Plastomenus ?thomasii, COPE, Syst. Cat. Vert. Eocene, New Mexico, 1875, p. 35. 



Plastomenus thomasii, COPE, Wheeler's Surv. W. looth Merid., iv, 1877, p. 49. (Not Trionyx thomasii 



Cope, 1872.) 



Plastomenus thomasi, COPE, Vert. Tert. Form. West, 1884, p. 125. (Not Trionyx thomasii Cope, 1872.) 

 Plastomenus serialis, COPE, Wheeler's Surv. W. looth Merid., iv, 1877, pp. 48, 51, pi. xxv, figs. 8-IO; 



Vert. Tert. Form. West., 1884, p. 123. HAY, Bibliog. and Cat. Foss. Vert. N. A., 1903, p. 453. 

 Platypeltis serialis, HAY, Amer. Geologist, xxxv, 1965, p. 337. 



The types of the present species appear to have been lost. We must, therefore, depend 

 for the identification of the species on the author's description and illustrations. Professor 

 Cope possest fragmentary remains of five individuals, which he had obtained from the Wasatch 



