444: G. JR. Wieland — Upper Cretaceous Turtles. 



From this numerous assemblage of species we naturally 

 come to ask how turtles with such thick shells as the Agom- 

 phids, the more naturally ascribed to land forms, came to be 

 so intimately associated with Osteopygis, Lytoloma, and the 

 various other semi-marine to marine turtles and other forms 

 which teem in all the Agomphus localities in the Upper Cre- 

 taceous marl beds of New Jersey. Being mostly small turtles 

 the heavy specialized shells would mainly serve as a protection 

 from the other larger and more powerful reptiles, which 

 swarmed along and into the bays and estuaries of the New 

 Jersey Cretaceous shore line, so that a salt water littoral 

 habitat is not precluded. But while no specimens of the 

 Marsh or other collections illustrating limb or cranial structure 

 have yet been referred to Agomphus, it would seem that at 

 least some of the species of the genus dwelt back from the 

 shore line along the streams, on the more or less sandy river, 

 ox-bow, or delta banks, and doubtless in the vast numbers 

 paralleling the Orinocan Podocnemis, the easy prey of the 

 jaguar, and once far more abundant on lower river courses 

 than now. From such locations many shells might be carried 

 forward to the shore front in flood time or in the course of 

 estuarial change. Also, if congregating in any considerable 

 numbers on the more nearly forest-free river banks, or on dune 

 slopes, at egg-laying time, many individuals might then be 

 either preyed on by other animals, or swept shoreward. It is 

 a fact of some slight bearing on such a conjecture that while the 

 Adocidse are much more numerous than the other Testudinates 

 of the marl beds, nearly all the limb bones recovered pertain 

 to the semi-marine to marine Osteopygid and Lytoloman series. 

 Moreover the abundance of the fossils of the marl beds is 

 probably not generally understood, since almost no specimens 

 have been secured in the past twenty-five years. Only a very 

 few per cent of the specimens uncovered in the marl pits, 

 when excavation was actively carried on thirty years ago, ever 

 made their way into the museums ; and these were all from 

 restricted areas, although these fossils were for the greater 

 part abundant everywhere in the several fossiliferous horizons 

 of the entire New Jersey marl belt. 



Yale Museum, New Haven, Conn. 



