486 FOSSIL TURTLES OF NORTH AMERICA. 
Key To THE SPECIES OF ASPIDERETES. 
A‘, Judith River and Laramie species: 
1. Shell of moderate size, broad; middle region of carapace with round pits, somewhat 
scattered; distal ends of costals crossed by furrows and ridges; plastron with 
twisted ridges ....... laa ae eae OIE At a aN foveatus 
. Shell large, Begader than long; pits numerous everywhere, in rows across distal ends 
so 
of costals; nuchal excavated in front................. .... coalescens 
Shell large, considerably broader than long; sculpture (ike that of aE scens, 
but less in rows across outer ends of costals; nuchal convex in front, straight 
behind. pees Pare jae ete as Ae ae rate eR AE a Met splendidus 
4. Shell nearly 2 as : broad as long, sculpture of carapace as in eo ae SceNS; nuchal straight 
or convex in front, shorter from side to side than splendidus; sculpture of plastron 
Ww 
finemthaneinucoalescens,. sase ae ee ec tee ee eee eee eee beechert 
5. Nuchal with thick abrupt free border; its width equal to half the distance from pre- 
neural to outer end; thickness at preneural border of type 4 mm.; pits not large... fontanus 
6. Nuchal with thick abrupt free border; width probably less than in 4. fontanus and 
thickness greater; pits large and irregular in arrangement .................. austerus 
7. Nuchal three-fifths as wide as distance from preneural to outer end; free border 
beveled off; bone at preneural border 7 mm. thick, preneural as wide as nuchal. . vorax 
A’. Arapahoe species: 
A species not well known. Pits of costal bones shallower than in the species numbered 
2, 3 and 4, and with less abrupt walls ................. a “Eee vagans 
a. _ Union and Puerco species: 
. Disk of carapace longer than wide; nuchal joined by its whole length to preneural 
and first costals; the outer end hardly reaching the rib of the first costal; 5 to 7 
pits Tay 2S Mime yas cee ecdeatar ster cq atniey cl otenabonmnyt aucun nc ene eee . Sagatus 
2. As in sagatus, but the outer end of the nuchal extending: across the ap of she 
first costal; 6 to 8 pits in a 20 mm. line on proximal ends of costals; only 3 or 4 
on distal ends ........... F edn spp smincn este ome dinets ; .. singularts 
Disk wider than long; sculpture Obscure | in town specimen, Bee. nee than in 
SAR QUUS) ateie tie nseie tie RCO Pom ees art ene, Cea er nen rae nassau 
4. Disk longer than ide: nich loosely joined to preneural and eastalss. fontanels 
Dehn sit trea. teers oe eae teeter ae ee eee De Sens ee eae -o 2. puercensts 
A‘. Bridger species: 
1. Preneural doubtfully present; a fontanel on each side of its position. Pits of cara- 
Pa Cen arp ctavediie ste Aeteiate ere vice cty a) tevscene cgteaen tetera ae eRe ge ae oe guttatus 
2. A well- -developed preneural aad no fontanels; sculpture eomewhae coarser than in 
either the preceding or the following species; second and third neurals about 
half as wide as long....... a : me . * .... ellrpticus 
3. A well-developt preneural and no foneanek: sculpture like that of guttatus; second 
and third neurals nearly two-thirds as wide as long....... f sc Loe. grangert 
Aspideretes foveatus (Leidy). 
Plate 89, figs. 1, 2; text-figs. 643, 644. 
Trionyx foveatus, Lerpy, Proc. Acad. Nat. Sci. Phila. vit, 1856, pp. 73, 3123 Amer. Jour. Sci., (2) 
xxul, 1856, p. 120; Trans. Amer. Philos. Soc., x1, 1360, p- 148, plate xi, figs. 1-3.—Cope, Synop. 
Ext. on Rept. and Aves N. A., in Trans. Amer. Philos. Soc., x1v, 1869, p: 0525 Bull. U. S. Geol. 
and Geog. Surv. Terrs., 1, 1879, No. 2, p. 29; Vert. Tert. Form. West, 1875, p. 260; Bull. U.S. 
Geol. and Geog. Sury. Terrs., 1877, in p- 573-—Lampg, 1902, Geol. Surv. Canada, Summary 
Rept. for 1gor, p. 81, plates i, 11; Cont. Canad. Palzont, 11 (4 to), pt. 1, p. 33, plate i, figs. 1, 2, 
text-hg. 1.—Hay, Bibliog. and Cat. Foss. Vert. N. A., p. 454, 1902.—Hartcuer, Bull. U.S. Geol. 
Surv. No. 2575 1008, 4p: 72: 
The specimens described by Dr. Leidy under the name Trionyx foveatus were collected by 
Dr. F. V. Hayden partly in the Judith River beds of Montana and partly in beds supposed to 
be of the same age, near Long Lake, in what is now Burleigh County, North Dakota. 
Those from ale Judith Riv er basin are described as consisting of small fragments of costal 
and sternal plates; and of these the proximal half of a costal plate and two , fragments of a 
hypoplastron are described and figured in Leidy’s paper of 1860 on ‘The Extinct Vertebrate 
