222 FOSSIL TURTLES OF NORTH AMERICA. 
Acherontemys heckmani Hay. 
Fig. 281. 
Acherontemys heckmant, Hay, Proc. U.S, Nat. Mus. xxu, 1899, p. 23, plate vi; Bibliog. and Cat. Foss. 
Vert. N. A., 1902, p. 446. 
The type of the present species belongs to the U.S. 
National Museum. It was found near Roslyn, State of 
Washington, in what is known as the Roslyn sandstone, 
of the Miocene formation. 
The carapace (figure 281) is broad and must have 
been rather deprest. There are no evidences of serrations 
on the hinder border of the carapace. The length is 
181 mm.; the width, 118mm. The median line appears 
to have a sort of keel, with low bosses. The sutures 
between the bones are distinct. There are 8 neurals. The 
first is nearly square; the eighth pentagonal and elon- 
gated; the others hexagonal. The nuchal is about twice 
as wide as long. The peripherals are nearly square, and 
those at the sides are placed opposite the ends of their 
respective costals. 
The sulci are distinctly imprest. The region of the 
nuchal scute is damaged. The vertebrals are extremely 
E. broad. The first has a width of 75 mm.; the second, 
3 go mm.; the third, 85 mm.; the fourth, 75 mm.; the 
fifth, 65 mm. ‘The costal scutes are correspondingly diminisht in transverse extent. The 
first, fourth, and fifth vertebrals are short. In the case of the fourth this is caused by the 
crossing of the sulcus between it and the third on the sixth, instead of on the fifth neural. 
Nothing is known regarding the plastron of this species. 
Fic. 281.—dAcherontemys heckmant. 
Carapace of type. 
Genus MACROCHELYS Gray. 
Three or four additional, or supramarginal, scutes on each side. Orbits lateral. Tail 
with small scales inferiorly (Boulenger). 
Type: Macrochelys temmincki (Troost). 
This genus is represented in the living fauna by the alligator snapper, a magnificent 
turtle that lives in the lower Mississippi River region. It reaches a large size and has a dis- 
proportionately large head. 
Macrochelys floridana sp. nov. 
Figs. 282-285. 
Macrochel ys flortdana, Hay, Bull. Amer. Mus. Nat. Hist. XXill, 1907, p- 847, figs. I-4. 
Four peripheral bones of perhaps as many individuals, a portion of the Jarman collection 
in Vanderbilt University, indicate a hitherto undescribed species of alligator snapper. It was 
found in what are probably Peace Creek beds, Hillsboro County, Fleada, 
A fourth left peripheral (fig. 282) is 46 mm. long, 34 mm. high, and 21 mm. thick. The 
upper and lower faces are of te odevate convexity mak meet in a subactite free border. At the 
hinder end of the bone is an excavation for a process of the hyoplastron, occupying nearly 
half the length of the bone. 
The right seventh peripheral (Ags. 283, 284) is 60 mm. long, 50 mm. high, and 25 mm. 
thick. The: upper border was anientced to the costal by a jagged suture. The slightly convex 
upper and lower faces meet to form an acute free border. As in M. te mmunck1, there is a 
long excavation for the hypoplastron. 
The ninth peripheral (fig. 285) has in the free border a notch and is tootht both in front 
and behind this notch. In M. temmunck: there is a single tooth, the one in front of the notch. 
This species differs from the living M. temmincki in having the free border of the fourth 
peripheral far less acute, the upper ee more convex, the rib-pit nearer the hinder end of the 
