Maryland Geological Survey 177 



provisionally referred to Priconodon crassus, but may possibly represent a 

 genuine stegosaur, otherwise unknown. 



Other Reptiles 



The fauna includes a crocodile, Goniopholis, found in the Wealden and 

 Purbeck beds of Europe and in the Morrison of Colorado and Wyoming, 

 The teeth are so similar to those from the western quarries that the 

 name Goniopholis affinis, the nearly related, is given to the Potomac type. 

 These are crocodiles of moderate size, 6 feet or more in length, and may 

 have resembled the modern genus Crocodilus, with its narrow snout, 

 quite closely in general appearance. In addition to the crocodile there 

 are occasional fragments of bone which give evidence of the presence of 

 a turtle as yet unidentified. 



summary 



The Arundel fauna represents, so far as known, three orders: Dino- 

 sauria, Crocodilia, and Testudinata. The presence of a ganoid fish is 

 also indicated. 



The dinosaurs represent all of the sub-orders, including two of the 

 heavier, megalosaurian carnivores, AUoscmrus and Creosaurus, and one 

 of the lighter, Compsognathoid type, Ccelurus. The quadrupedal Sauro- 

 poda are represented by at least one genus, possibly two, Pleuroccelus 

 and Astrodon, including two or three species in all, while of the Ortho- 

 poda there are two, one the unarmored Dryosaurus, the other, Pricono- 

 don, evidently belonging to the armored group or Stegosauria. 



The dinosaurs show none of the remarkable over-specialization of the 

 later Cretaceous types, but, on the contrary, represent the order at the 

 crest of the evolutionary wave, before signs of decadence set in. Un- 

 fortunately, owing to an almost utter dearth of terrestrial Jurassic de- 

 posits, nothing is known of dinosaurian evolution in America from 

 Newark time until we come to the horizon under consideration. In 

 Europe the record, though still meagre, is more complete; but it repre- 

 sents in every instance more primitive types than those of the Arundel 

 and the Morrison. 



