Merriam.] 



Triassic Irh tli yopterygia . 



97 



distal hook is in consequence of this somewhat longer and the 

 anterior notch deeper. The clavicle is long and slender. The 

 interclavicle is unknown. 



The anterior portion of the vertebral column runs up to the 

 foramen magnum and is probably complete . Immediately behind 

 the back of the skull, and in close proximity to it, are two small 

 indeterminate ossicles in the position which the separate pieces 

 of the upper arch of the atlas would naturally occupy. Follow- 

 ing them is a vertebra-like body, which does not seem to be 

 biconcave. Its dimensions are nearly the same as those of a 

 deeply amphiccelous centrum immediately behind it, and it is 

 possibly the atlas. The first certainly determinable vertebra is 

 the second large element behind the parietals. It is deeply bicon- 

 cave, the excavated end surfaces sloping gradually to the center. 

 On one side of this centrum there is an oblique truncation at each 

 end. Against one of these there rests a small piece of bone which 

 is probably an intercentrum . The second centrum behind this 

 one, the fourth, is well exposed, showing the sides and anterior 

 end. The lower side of the anterior end is produced downward 

 as an apophysis, against the anterior face of which an intercentrum 

 has rested. The inferior apophysis gives to the front face of 

 this centrum a height as great as the breadth and makes the 

 cross-section pentagonal. On this centrum, as on the three follow- 

 ing it, the diapophyses are high and broad. They narrow toward 

 the top and are connected with the upper articular surfaces. The 

 parapophyses are relatively small, their height being considerably 

 less than half that of the diapophyses. On the eighth the 

 parapophysis is abnormally large and is also entirely but of its 

 natural position, being on the posterior margin. On the ninth 

 it is in its normal position and very small. 



The upper arches, which are well shown on the fifth and 

 seventh, are high and rather slender. The spines are very thick, 

 being almost circular in cross-section. The zygapophyses are 

 large and strong. The bases of the pedicels project laterally 

 over the diapophysial ridges. 



Two or three of the ribs which are present show both the 

 capitulum and tuberculum. The former is, however, in all cases 

 very small. On several other well preserved ribs there is only a 



