132 THE PERMO-CARBONIFEROUS RED BEDS OF 



last of the water. The fact that the bones are found in nodular concretions 

 or limy clay gives support to this idea of desiccation and the concentration 

 of the lime salts in the water. Associated with the skeletons of Lysorophus 

 are the skulls of Gymnarthrus , Cardiocephalus (?), and the form called by 

 Broili Diplocaiilus pusillus, but they are not at all common. No bones of 

 larger animals have been found with those of Lysorophus in Texas. It is 

 probable that all the creatures that could do so escaped from the drying pools, 

 but that Lysorophus, either because of its inability to leave the water or 

 because it sought protection by burrowing in the mud, perished in the com- 

 plete desiccation. If this idea seems probable, it may be accepted as con- 

 firmation of the amphibian nature of Lysorophus, for if it were a reptile it 

 would have been far easier for it to escape from such surroundings. 



No skeleton recovered is sufficiently complete to warrant an exact esti- 

 mate of the length, but it certainly was not greater than 25 to 30 centimeters. 



The author recognizes that Lysorophus is primitive in many respects, 

 but regards it as far too specialized to occupy the ancestral position assigned 

 to it by Broili, and thinks of it rather as a very highly adapted member of a 

 primitive group, a terminal member of a side-line of evolution. 



Crossotelos. — This genus has been foiind only in a single locality, Orlando, 

 Oklahoma, but occixrs there in considerable numbers. It is possible that the 

 individuals suffered a fate similar to that of the members of the genus Lysoro- 

 phus. Far too little is known of the skeleton (only a part of the vertebral 

 column and a few limb bones) to enable any full idea of the shape or size to 

 be formed. It had a long tail, expanded in the vertical plane, and was con- 

 sequently a good swimmer. The limbs were of fair size. The chief peculiar- 

 ity of this genus is the development of large, thin dorsal and ventral processes 

 on the caudal vertebrae, and the closely inosculating, serrate spinal processes 

 of the dorsal vertebrae. These structures are only matched in Osteocephalus 

 from the Linton beds, upper Pennsylvanian, of Ohio, Keraterpeton from the 

 Upper Carboniferous of Ireland {Scincosaurus from the Permian of Bohemia), 

 and Urocordylus and Keraterpeton from the Permian of Bohemia. This 

 resemblance may be due to parallel evolution, but if so it is a very remarkable 

 case. Osteocephalus was elongate and snake-like in form, and Keraterpeton 

 was, as restored by Fritsch, a long-bodied, short -legged form, with a short, 

 round head, and a tail longer than the presacral portion of the body. It is 

 probable that Crossotelos was not very different from the last-mentioned 

 genus in shape. 



Cricotus (plate 20, fig. i). — This genus is the only known form from the 

 Permo-Carboniferous fauna which can be considered as having adopted an 

 active, predaceous, largely aquatic habit of life. The long and slender body, 

 terminating in a long tail with elongate chevrons and spinous processes, the 

 short limbs, with poor articular surfaces, and the elongate skull, with numer- 

 ous sharp, grasping teeth, all remind us strongly of the essentially aquatic 

 reptiles. 



