36 FOSSIL TURTLES OF NORTH AMERICA. 
THE GEOLOGICAL DISTRIBUTION OF THE TURTLES. 
In tables 1 and 2 the writer has endeavored to present in as accurate and effective 
a manner as possible the chronological distribution of the fossil turtles of North 
America, with the positions of the turtle-bearing beds and the level at which each 
species has been found. ‘Table 1 represents the principal divisions and subdivisions 
of the Mesozoic age, except the Triassic, while table 2 deals in hke manner with the 
Cenozoic. No small difficulty is experienct in the preparation of such tables. The 
limits of the larger formations and the periods which they represent have not 
received general acceptance; and when we come to consider the smaller divisions 
and the correlation of deposits in distant regions there are in many cases widely 
divergent views. Again, in the collection of the fossils there has often been too 
little care exercised in preserving records of localities and levels. An interroga- 
tion mark (?) preceding any generic name indicates that the species immediately 
succeeding possibly does not belong to the level indicated. 
‘TABLE 1.—Princt pal divisions of the Furassv and Cretaceous, with the Species of turtles known from each, 
Denver. | ?Glyptops depressus. 
Arapahoe. Adocus? lineatus, Plastomenus? punctulatus, P. insignis, Aspideretes vagans. 
Baéna marshi, B. hatcheri, Eubaéna cephalica, E. latifrons, Thescelus insil- 
iens, T. rapiens, ?Naiadochelys ingravata, Basilemys sinuosa, Compsemys 
victa, C.? obscura, Helopanoplia distincta, Aspideretes foveatus, A. beech- 
eri, A. austerus, A. fontanus, A. vorax. 
Laramie. 
Fox Hills. No turtles known. 
Bear Paw. No turtles known. Eastern Recion. 
= 7 (Greensand, etc., approximately 
Baéna_ callosa, B. equivalent to Pierre, etc.) 
antiqua, Boremys — Bothremys cooki, Taphrosphys sul- 
pulchra, Neuranky- catus, T. longinuchus, T. leslianus, 
lus eximia, Chari- T. strenuus, T. molops, T. nodo- 
temys captans, sus, T. dares, Amblypeza entellus, 
Polythorax missuri- Osteopygis emarginatus, O. gibbi, 
SOSIS, Basilemys O.robustus, O. chelydrinus, O.ero- 
variolosa, B. im- sus, O. borealis, O. platylomus, oO. 
Judith River. bricaria, ?Compse- sopitus, Catapleura repanda, C. 
Gere ae ponderosa, Peritresius _ornatus, 
oot Pierre. specta rr aston Lytoloma angusta, L. jeanesi, Die 
menus costatus, wielandi, Erquelinnesia molaria, 
Aspideretes fovea- Rhetechelys  platyops, ?Neptu- 
Mesongiee tus, A. coalescens, | nochelys tuberosa, Atlantochelys 
A. splendidus, A. | mortoni, Adocus beatus, A. puncta- 
beecheri. | tus, A. lacer, A. syntheticus, A. 
| agilis, A. pravus, Agomphus turgi- 
=|| dus, A. petrosus, A. tardus, A. 
Clagget. Toxochelys latire- pectoralis, A. firmus, A. masculi- 
mis?, Porthochelys | nus, Zvygoramma striatula, Z. micro- 
Eagle. browni, Archelon | — glypha, Homorophus _ insuetus, 
ischyros, A. marsh. Amyda? prisca, A.? halophila. 
Toxochelys latiremis, T. serrifer, T. brachyrhina, T. steno- 
Niobrara pora, T. elkader, T. procax, T. bauri, Cynocercus incisus, 
Porthochelys laticeps, Protostega gigas, P. potens, P. 
advena. 
Benton. Glyptops pervicax, Desmatochelys lowi. 
Dakota. No turtles known. 
Washita. Glyptops? belviderensis. 
. Lower Fredericksburg. No turtles known. 
Cretaceous. 
Trinity. Glyptops celatus (In Potomac beds). 
Morrison. Glyptops plicatulus, Probaéna sculpta. 
Jurassic. Unk papa. No turtles known. 
Sundance. No turtles known. 
