248 S. W. WILLISTOX. 



proximal ends of them are seen. I do not think that the follow- 

 ing vertebrae bore ribs, or, if so, they were much shorter. I can 

 find no indications of such. In the restoration, these caudal ribs 

 are shown directed backward, as in the matrix. Doubtless in life 

 they were directed more downward, indicating a thick basal por- 

 tion of the tail, probably compressed from side to side. Beyond 

 the eighth visible caudal there is a break in the series, the only 

 indication of contemporary extraneous force shown in the entire 

 skeleton ; and this may have been due to the fact that this part 

 lies somewhat under the right hind leg in the nodule that is, 

 if the skeleton was originally fossilized in a prone and not supine 

 condition. Following this gap there are three articulated verte- 

 brae in line with the curvature of the basal portion of the tail. 

 They are more slender than the preceding ones and clearly lie 

 in their original position, the intervening five vertebrae having 

 been dislodged, fragments of which are still preserved near the 

 break. The extreme tip of the tail came near the margin of the 

 nodule, at or below the tip of the muzzle, and has been 

 destroyed by the erosion of the nodule. Perhaps a half dozen 

 very small vertebras are missing here, making altogether about 

 twenty-five vertebras for the number in the tail, or for the entire 

 column about fifty, with a possible error of three or four more. 

 The dorsal ribs have an expanded proximal end, but without 

 distinct differentiation into head and tubercle. The first one visi- 

 ble is attached to the vertebra concealed in part by the caudal end 

 of the interclavicle, that is, the seventh or eighth of the series. It 

 is altogether probable that the first four or five ribs were shorter, 

 with expanded distal ends, as in Labidosaitms. From the eighth 

 to the seventeenth the ribs lie nearly parallel on the right side, on 

 the left bein crowded more together at their ends. The longest 

 of them measure forty-six millimeters along their considerable 

 curvature. They are slender throughout. The broken ends of 

 the eighteenth and nineteenth are visible in the matrix, but little 

 if any shorter than the preceding ones. A fragment of what 

 should be the twenty-first or twenty-second is also visible on the 

 right side, but its length is not determinable. I have, therefore, 

 shaded the last four ribs in the restoration, and it is possible 

 these vertebrae were entirely ribless, as I have decided they were 

 in Labidosaurus. 



