THECODONTIA. 281 



and never having been, the living organisms which they 

 represented — notions which were then advocated under the 

 sounding phrase of " plastic force," as they have lately been 

 under that of " prochronism." Spener's only doubt was, 

 whether the reptile had been a crocodile or a lizard ; bnt he 

 inclined to the former view, on account of the proportions of 

 the head to the trnnk. 



The head equals one-third the length of the" neck and 

 trunk, and resembles in shape a long, slender, obtusely 

 pointed cone ; it has strong straight jaws, armed with sub- 

 slender, sub-equal, straight, conical, sharp-pointed teeth ; about 

 1 8 on each side of the upper, and 1 6 on each side of the lower 

 jaw, implanted in a single close-set series of sockets. A 

 small and short atlas is succeeded by six cervical vertebras, 

 remarkable for their size and strength, the 4th being almost 

 one-third the length of the lower jaw ; the 6th and 7th de- 

 crease in size, and the 8th supports a rib of the thickness of 

 those of the trunk. In the preceding neck-vertebrae, the 

 ribs present the long and slender characters of the bone ten- 

 dons of the neck muscles, with which they are associated in 

 function. Fifteen or sixteen vertebrae, about half the length 

 of those of the neck, intervene, in Spener's specimen, be- 

 tween the 7th cervical and the sacral vertebrae. The sacrum 

 equals four of the crushed vertebrae in length ; twenty-one 

 caudal vertebrae are preserved ; but Link's and later ac- 

 quired specimens indicate the number to have exceeded forty. 

 The neural spines of the anterior caudal vertebrae are rather 

 long, sub-quadrate, truncate ; but they gradually expand 

 above, and at the 10th caudal a notch appears, which, deep- 

 ening as the vertebrae recede from the trunk, divides the spine 

 into two equal diverging processes, a structure peculiar to the 

 Protorosaur. The haemal arches articulate with the vertebral 

 interspaces, and have longer and more slender spines, simply 

 expanded at their end. Both fore and hind limbs are penta- 



