” 
TRIONYCHID. 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 
TUE Se noe re ee PN nse SN rch Coed ied Lites suse as 2? yaad s (0S (Seen biahe Bie mae cine deg aca trionychotdes 
4. Carapace as broad as long; nuchal hardly half the width of the carapace; a, : 
smooth band along its front; sculpture coarse near raatcolbt Vana ae oe eee heteroglypta 
5. Carapace broader than long; nuchal more than half the width of carapace; 
pitted to free border; sculpture as in DECCCOMN Purser am Samy choses os: postera 
6. Carapace broader than long; nuchal not half the width of the carapace; 
sculpture like that of heteroglypta Re ee chap mi uetame: ntepers ie eile \ar eels et wars : extensa 
A‘. Oligocene species: 
1. Carapace thin, broader than long; nuchal 0.6 the width of the carapace; a 
fontanel each side of first neural.......... shes eee toes ah ete . leucopotomica 
A®. Pliocene and recent species: 
1. Carapace elliptical; longer than wide; nuchal about half the width of the cara- 
pace; sculpture rather coarse..........-.-- Sakic oatutle aun casinene ine ferox 
Platypeltis antiqua Hay. 
Fig. 693. 
Platypeltts antiqua, Hay, Bull. Amer. Mus. Nat. 
Hist., XxX111, 1907, p. 859, fig. 18. 
The specimen which represents this species 
appears to have been collected for Professor eae 
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 peor 
5 neural bones. Some other bones are buried 
in the very refractory matrix. The catalog 
number 1s 1036. : : 
The carapace | Neural. | Length. | Width. | res 
(fig. 693) had a ‘ Bese!) 
length of about ies a aces U 
5 3 | 16 | 9 ra a in 
1oo mm. and a4 | 15 | 8 a cece, os 
a = / ee é Rane eee 
width of 78 mm.; | 5 mo 6 | {les < 3 2 = 
= 7 
but the ends of — ge rac Sas 
the ribs extended beyond the disk at least 18 
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. 
.. 
y 
y 
' 
' 
4 
\ 
nM 
Fic. 693.—Platy peltis antiqua. Carapace 
of type. X 3. 
Platypeltis serialis (Cope). 
Plate 98, fig. 13; plate 109, figs. 1-4; text-figs 694-696. 
Trionyx, Letpy, Contrib. Ext. Vert. Fauna West. Terrs., 1873, p. 180, plate xvi, fig. 11. 
Plastomenus ?thomasii, Corr, Syst. Cat. Vert. Eocene, New Mexico, 1875, p. 35- 
Plastomenus thomasti, Corr, Wheeler’s Sury. W. tooth Merid., 1v, 1877, p. 49. (Not Trionyx thomasi 
Cope, 1872.) 
Plastomenus thomast, Core, Vert. Tert. Form. West, 1884, p. 125. (Not Trionyx thomastt Cope, 1872.) 
Plastomenus serialis, Copr, Wheeler’s Surv. W. tooth Merid., 1v, 1877, pp. 48, 51, pl. xxv, figs. 8-10; 
Vert. Tert. Form. West., 1884, p. 123.—Hay, Bibliog. and Cat. Foss. Vert. N. A., 1903, p- 453- 
Platy peltts sertalis, Hay, Amer. Geologist, XXXV, 1905, Pp. 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 
