!)() 



University of California. 



[Vol. 3 



the ratio is 1:2.21. The variation in the relation of width 

 to height of centra between the anterior and posterior ends 

 of the column is much the same in perrini as in osmonti. The 

 centra are deeply excavated on the anterior and posterior 

 surfaces, which slope sharply from the margins to the centre. 

 In those which could be examined the bony partition is not 

 perforated, though it may be very thin. 



The character of the rib articulation is not essentially different 

 from the typical form described for the genus. The fifth to the 

 fourteenth vertebrae present are covered by ribs and could not 

 be examined. The fourteenth to the nineteenth are twisted away 

 from the arches, and turned so that the inferior surfaces are 

 uppermost. The ribs which covered these centra were removed 

 and a cut made below the column to expose the dorsal surfaces. 

 The rib articulations were successfully uncovered on the sixteenth 

 to nineteenth and were found to be the same as those on the 

 twenty-fifth (PI. 5, fig. 2). The paraphophysis is gone, and 

 the diaphophysis is connected with the superior articular surface. 

 The lower side of the diapophysis, which swings forward to the 

 anterior margin of the centrum, is somewhat narrower than in 

 osmonti. On the twenty- seventh centrum the diapophysis is 

 separated from the superior articular surface by a wide space. 

 Unfortunately the twenty-sixth is turned over, and could not 

 be examined without injury to the upper arch. 



Opposite the pelvic girdle, or at about the fortieth vertebra, 

 the diapophyses reach the lower side of the centra. They have 

 here, however, nearly the same form as on the twenty- seventh. 

 Back of the pelvic arch they rapidly become shorter, changing 

 to an elliptical or circular outline. In this region they also 

 move up the sides of the centra. On the sixtieth centrum they 

 are about half way up the side. Beyond this point they could 

 not be traced with certainty. 



The upper arches do not vary greatly in height between the 

 cervical and anterior caudal regions. Those of the anterior and 

 middle dorsal region attain a slightly greater height than the 

 others. In the cervicals and anterior dorsals the spines are 

 relatively thicker than elsewhere, and the pedicels are much 

 extended laterally. Back of the twenty- sixth vetebra, where 



