28 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



end, in the position of the concavity of most reptilian forms. This is most striking 

 and leads to some doubt as to the correct identification of the bone; it resembles the 

 tibia of other forms, but is far too large to be a tibia of this creature, and as both 

 bones are present and show this character, its determination seems certain. The 

 shaft is short and thick, the lower end is imperfectly divided into two faces. 



The tibia is similar in form to that of Diadectes and resembles quite closely the 

 femur in general form. The lower end has two distinct faces at an angle of 45 . 



The fibula is probably represented by the two ends; little can be made out be- 

 yond its exceptional heavy form. 



Fragments of the skull with some poorly preserved teeth show that the skull 

 was in general form like Diadectes. 



Measurements. 



mm 



Length of the series of vertebrae 380 



Length to posterior end of sacral vertebra 230 



Length of ilium on midline 54 



Length of femur 47 



Width of distal end of femur 37 



Length of tibia 36 



Length of a mid dorsal rib 127 



Length of an anterior chevron 24 



This creature seems to have carried the peculiarities of Diadectes to an extreme. 

 The vertebral column is more closely knit and even shorter. The limb bones are 

 heavy and very short. The tail was moderately long, but very thin and fairly high. 

 The whole appearance must have been that of a short, low, and very wide creature 

 with broad stumpy legs. The evident great strength, coupled with the essential 

 weakness of the free neural spines, leads to the suggestion that the specimen is that 

 of an immature animal. 



Family BOLOSAUR1DAE Cope. 



Cope, Proc. Am. Phil. Soc, vol. xvu, 1878, p. 529. 

 Case, Bull. Am. Mus. Nat. Hist., vol. xxm, 1907, p. 652. 



Original description: "Bolosaurus will form the type of another family charac- 

 terized by the transverse position of the crowns of the teeth, under the name Bolo- 

 saurtdce. 



Revised description (Case, 1907): "Small Cotylosaurians with the cheek teeth 

 elongate transversely and with a prominent cusp, in the upper series on the outer 

 edge and in the lower series on the inner edge; the cusps showing slight wear in 

 mature specimens. The family is distinguished from the Pariottchida? by the pres- 

 ence of the cusps on the teeth and by the presence of but a single row in the lower 

 jaw, and from the Diadectidce by the presence of an elongate parasphenoid rostrum 

 and a prominent outer process of the pterygoid bearing a row of teeth on the lower 

 edge." 



Revised description: 



1. Skull smooth or slightly rugose. 



2. Pineal foramen small. 



3. Occipital condyle rounded. 



4. No armor. 



5. Ribs not expanded. 



6. Body low; limbs short, not heavy. 



7. Not determinable. 



