248 



FOSSIL TURTLES OF NORTH AMERICA. 



Mr. Barnum Brown, on Hell Creek, Montana. Fragments of costals scarcely, if at all, to 

 be distinguish! from them are found in the collection made in the Judith River region for 

 Professor Cope, by C. H. Sternberg, in 1876. It is the writer's opinion that it is unsafe to 

 identify as belonging to Adocus lineolatus specimens from the Judith River and the Laramie 

 beds before far better materials of the species have been collected from the type locality. And 

 when these better materials have been secured from Bijou Creek, better specimens than yet 

 obtained must be secured from the other formations mentioned. It is improbable that the 

 same species continued from the Judith River epoch to the Arapahoe epoch. Meanwhile, 

 even good fragments are worth preserving. 



The specimen referred to above as having been collected by Sternberg from the Judith 

 River region forms No. 6105 of the American Museum. It belonged to the third or the fifth 

 costal. Its width is 32 mm.; its thickness, only 3.5 mm. There is no thickening along the 

 middle on the under side corresponding to the rib. The outer surface is crost by the costo- 

 vertebral sulcus. The ornamentation resembles in pattern that of Cope's Compsemys im- 

 bricaria (Basilemys imbricaria), and Cope has so labeled the bone; but the size of the areolae is 

 considerably smaller, there being 4 pits in a line 5 mm. long, instead of 3 or less. The ridges 

 between the areolae are low and run at right angles with the sutural borders of the bone. 



A fragment of a costal from Hell Creek, Montana, collected by Mr. Barnum Brown, is 

 catalogged under the number 1014 of the American Museum. The costal is 36 mm. wide 

 and 5 mm. thick . The sculpture is similar to that of the Judith River specimen just 

 described, but is more obscure. 



A peripheral, the second of the left side, has the number 1014, but it belonged to a much 

 larger individual. It is represented by figs. 308 and 309. The bone is 55 mm. high, 48 mm. 



along [the free border, and 32 mm. along the 

 costal border. Fig. 309 represents the border 

 joining the first peripheral, the greatest thick- 

 ness being 16 mm. The sutural border for the 

 third peripheral has a maximum thickness of 

 24 mm. The sculpture has the pattern and the 

 fineness ascribed to the costal. It resembles 

 greatly that of the fragments numbered 6103 



FIGS. 308 AND m .-Adocus lineolatus. Periph- A " M ' N " H - and described under Basilemys 



- ------ imbricaria. 



No. 6107 A. M. N. H. includes a fragment 

 of a costal plate and another of a plastral bone 

 which were collected for Professor Cope, in 1877, 



by Mr. J. C. Isaac, in the Laramie of Converse County, Wyoming. The sculpture of these 



bones resembles closely that of A. lineolatus, type. 



Genus AGOMPHUS Cope. 



Shell thick and heavy in the known species. Free borders of the carapace thickened and 

 obtuse. Exposed surfaces of the shell not pitted. Hinder marginal scutes not rising on the 

 costal bones, except slightly in one species. Inframarginal scutes present. The pectoral 

 scutes extending forward to the hinder end of the epiplastrals. Intergulars not known. Nuchal 

 with costiform processes. Rib-heads more strongly developt than in Adocus. 



Type: Agomphus turgidus Cope. 



The genus Agomphus was founded by Cope in 1871 (Proc. Amer. Philos. Soc., xn, p. 46) 

 having A. turgidus as the type. The only character given was the apparent lack of gomphosis 

 between the costals and the peripherals; an insufficient character, if a true one. In 1882 

 (Proc. Amer. Philos. Soc., xx, p. 145) Cope placed Agomphus with Dermatemys in the Emy- 

 didae, characterizing it as possessing 2 anal marginal scutes, a series of inframarginals, and 

 with the lobes of the plastron wide. The same views are repeated in that author's Vertebrata 

 of the Tertiary Formations of the West, in 1884. In both the publications referred to, the 

 genus Amphiemys was placed among the Adocidae. Baur in 1888 (Zool. Anzeiger, XI, p. 595) 

 reduced Amphiemys to the position of a synonym of Agomphus and arranged the latter under 



eral and section. x. No. 1014 A. M. N. H. 



308. Second left peripheral. 



309. Section of same peripheral at union with third. 



