THE SUBCLASS PARAPSIDA 261 



arboricolous, insectivorous, lizard-like reptile from the Lower Per- 

 mian of Texas. Of Kadaliosaurus, unfortunately, the skull is un- 

 known. Its slender bones were less hollow, and it has also numerous 

 parasternal ribs, unknown in Araeoscelis. 



Lower Permian. Araeoscelis Williston, Texas. Kadaliosaurus 

 Credner, Germany. 



Family Protorosauridae. Elongate reptiles with long neck and 

 hind legs and hollow bones, from three to five feet in length. Skull 

 imperfectly known, probably with an upper temporal opening only. 

 Sclerotic plates in orbits. Prevomers, palatines, and pterygoid with 

 small teeth. Vertebrae amphicoelous, with persistent intercentra. 

 Seven cervicals, sixteen to eighteen dorsals, two or three sacrals, and 

 a long tail. A single coracoid. Pelvis more or less plate-like, with 



Fig. 181. Skeleton oi Protorosanrus (Protorosauria), modified from Seeley. 

 About one tenth natural size. 



probably a small pubo-ischiatic vacuity. Ribs single-headed, articu- 

 lating with centrum, those of the cervical region very slender. Epi- 

 podials about as long as propodials, the hind legs much longer than 

 the front. Humeri with ectepicondylar (?) foramen; nine or ten 

 carpals, seven tarsals ; phalangeal formula primitive, the digits long. 

 Numerous abdominal ribs. 



Although the first-described fossil reptiles, the protorosaurs are 

 still imperfectly known in the details of their structure, especially of 

 the skull, pectoral, and pelvic girdles. In the elongation of the neck 

 and the slender legs Protorosaurus very much resembles Araeoscelis, 

 and doubtless had similar habits, whether or not the structure of the 

 skull was the same. The numerous known specimens of Protoro- 

 saurus differ so much from each other that it is not at all improb- 

 able that they represent different genera. 



Aphelosaurus is still more problematical, inasmuch as all that is 

 known of it are the trunk and limbs. The limbs resemble those of 



