REPTILIA : CASE A no 



So far as this series can be compared with that of No. 657, many 

 of which have not yet been cleaned from the rather hard incrusting 

 matrix, they agree absolutely, the vertebrae of No. 657 being 

 possibly a trifle larger than those of No. 655. The second presacral 

 of No. 657 is shown in Plate XIV, Fig. 2. The vertebrae through- 

 out are easily distinguishable from those of all other genera, save 

 Trispondylus perhaps. Very remarkable is the disparity in size 

 between the most anterior and the most posterior of the presacral 

 series, a difference so great that had. the vertebrae been found dis- 

 connected and isolated, they would not have been associated in 

 the same individual — the diameters of the third vertebrae being 

 at least a third less than those of the first presacral, as may be seen 

 by comparison of the axis shown in Plate XIV, Fig. 1, with the 

 second presacral of the same individual shown in same plate, 

 Fig. 2. The centrum of the first presacral is only a little broader 

 than long, concave below, "pinched in" on the sides so as to give 

 a rounded, lower border, somewhat keel-like, but with no indication 

 of the median fossa, so characteristic of the caudal centra. The 

 centra become rather rapidly narrower, the tenth or eleventh 

 presacral being nearly twice as long as broad, deeply concave on 

 the sides but not keel-like below. The length begins to diminish 

 noticeably after the twelfth, or the one bearing the longest ribs. 

 Thenceforward the centra diminish gradually in size, both trans- 

 versely and longitudinally, as will be seen by comparison of the 

 third with the last in Plate XV. The spines are of nearly uniform 

 length throughout, perhaps a little shorter anteriorly. They are 

 oval in cross-section, and a little dilated at the extremity, the top 

 subcircular in the most posterior ones, elongated oval in the middle 

 and anterior ones, and beginning with the tenth or eleventh 

 presacral they become relatively more dilated antero-posteriorly 

 through the thoracic region. The zygapophyses are broad and 

 flat posteriorly, narrower anteriorly, their articular surfaces looking 

 at only a moderate angle outward or inward. The centra are, 

 of course, deeply conically concave, with a narrow continuous 

 notochordal canal through the middle. The figures of the first 

 seven vertebrae were made, as stated, from another specimen. 

 No. 657. The matrix of this specimen is unusually hard and the 



