REPTILIA: CASEA 123 



tinuous with the sacrum; a fourth specimen found isolated, but 

 which in all probability belongs with those of the other skeletons, 

 includes a connected series of caudal vertebrae, eighteen in number, 

 beginning just where the spine is becoming obsolete. This last 

 specimen has been used in connection with the series of No. 

 657. It is possible that one or two vertebrae may have intervened 

 between the vertebrae as united, but this is not very probable, 

 since the junction is made where all the characters seem to agree. 

 The last vertebra of No. 658 measures six mm. in transverse 

 diameter; continuing the same taper, seven vertebrae have been 

 modeled from plaster and added in the restoration, making the 

 approximate number of vertebrae in the entire tail fifty in number, 

 or almost the same as that of Varanosaurus, where the complete, or 

 nearly complete, series of a single individual was found intact. 

 The tail, however, as a whole, like the preceding part of the spinal 

 column, is stouter than in Varanosaurus, and less compressed. 



Co-ossified ribs, or vestiges of ribs, are found on the first seven 

 or eight of the series. The first three pairs extend quite the width 

 of the sacrum, thence decreasing rapidly in length till they are 

 mere tubercles. The second pair, the largest, are directed outward, 

 and then horizontally backward, to a point about opposite the 

 middle of the next vertebra. The third pair, more slender, are 

 directed outward, with an anterior curvature, barely escaping the 

 tips of the preceding ones. Like the preceding ribs, the caudal 

 ribs are double-headed, and are co-ossified with arch and centrum ; 

 on the hinder ones the tubercle seems to be in large part attached 

 to the centrum. The spines, so far as they were recovered from 

 the matrix, become successively shorter, terminating as a mere 

 tubercle at about the eighteenth vertebra; and they are quite thin 

 at the extremity, slightly more thickened anteriorly. Beginning 

 with the third in No. 656, the fourth in No. 655, the underside 

 of the centrum has a distinct longitudinal median groove or 

 fossa, decisively distinguishing the genus from all others. This 

 fossa is narrow and well marked, extending to the last of the 

 series as preserved, and doubtless quite to the extremity of the 

 tail. From the third or fourth to the seventh or eighth, the 

 centra are very distinctly shorter below than above, and both 



