222 



FOSSIL TURTLES OF NORTH AMERICA. 



Fig. 281. Acherontemys heckmam. 

 Carapace of type. X^. 



Acherontemys heckmani Hay. 



Fig. 281. 



Acherontemys heckmani, Hay, Proc. U. S. Nat. Mus. XXII, 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, 1 18 mm. 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 



broad. The first has a width of 75 mm.; the second, 



90 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. 



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. 

 Macrochelys floridana, Hay, Bull. Amer. Mus. Nat. Hist, xxiii, 1907, p. 847, figs. 1-4. 



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, Florida. 



A fourth left peripheral (fig. 282) is 46 mm. long, 34 mm. high, and 21 mm. thick. The 

 upper and lower faces are of moderate convexity and meet in a subacute 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 (figs. 283, 284) is 60 mm. long, 50 mm. high, and 25 mm. 

 thick. The upper border was articulated to the costal by a jagged suture. The slightly convex 

 upper and lower laces meet to form an acute free border. As in M. temmincki, there is a 

 long excavation tor the hypoplastron. 



The ninth peripheral (fig. 2X5) has in the free border a notch and is tootht both in front 

 and behind this notch. In M . temmincki 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 face more convex, the rib-pit nearer the hinder end of the 



