432 Loomis — JReptiles from the Titanothere Beds. 



(Platycarpus ?) consisting of 20 vertebrae, 2 J paddle pieces and 

 some fragments, 28 bones in all. All of these occurred in con- 

 cretions similar in shape, size and structure to those in the Ft. 

 Pierre but lighter in color, and stained with haematite on the 

 outside and wherever weathered. The baculites occurred over 

 an area about three miles in diameter, in many places in great 

 abundance. However, in none of the neighboring localities 

 did any trace of these fossils occur ; although the Titanothere 

 beds were carefully examined for more such material. The 

 species are those not uncommon in the neighboring Ft. Pierre. 

 The underlying Oligocene is mostly the typical white chalk of 

 the formation, with near the base some beds of sand and gravel. 

 In the chalky beds about six feet above the base of the White 

 River formation, and 25 feet below the Ft. Pierre fossils, 

 Titanotherium bones were collected. The beds are clearly 

 Oligocene : the fossils clearly Cretaceous. 



But one explanation is at all adequate, and that is, that the 

 river depositing the Titanothere beds supplemented the load of 

 mud its waters were carrying by washing out the Ft. Pierre of 

 its banks, and carried this along, depositing it with the rest. 

 The distance probably was not great. The current must have 

 been rapid however ; for the concretions were carried with the 

 fossils. This is certain, for the baculites would never stand 

 transportation without breaking, except in the concretions. 

 Then 28 bones of a Mosasaur were not excavated, carried along 

 and redeposited together, unless held by a matrix. The size of 

 the concretions is from one to three feet in diameter, indica- 

 ting what the force of the current must have been. Inasmuch 

 as the nature of the material making up the Titanothere beds, 

 and the contained fauna, have already been considered sufficient 

 evidence for the river origin of these beds, such a case of rede- 

 position seems to me conclusive evidence of the flood plain 

 formation of the beds. And the foregoing has given two at 

 least of the forms living in the river. 



EXPLANATION OF FIGURES. 



Fig. 1. — Crocodilus prenasalis nov. spec, snout of specimen No. 1 seen 



from above, x J. 

 Fig. 2. — Same seen from below, x -J. 

 Fig. 3. — Crocodilus prenasalis nov. spec, specimen No. 2 dorsal vertebra. 



xi 



-Tibia of same, x \. 

 ■Femur of same, x %. 

 -Astragalus of same, x \. 

 -Dermal scute with two margins sutured, x \. 

 -Dermal scute with one margin sutured, x \. 

 -Dermal scute which lay free in the skin, x \. 

 —Chrysemys inornata nov. spec, carapace. x f . 

 — " " " " plastron, x f . 



Fig. 



4.- 



Fig. 



5.- 



Fig. 



6.- 



Fig. 



7.- 



Fig. 



8.- 



Fig. 



9.- 



Fig. 



10. 



Fig. 



11 



