MEASUREMENTS OF THE DORSAL VERTEBRAE.

1. Length of centrum to rim of ball38 millim.
Transverse diameter of ball20
Vertical diameter of ball19
Height of spine above floor of neural canal48
Extent of articular surface of transverse process 30
Width of spine28
4.Length of centrum to rim of ball41
Transverse diameter of ball20
Vertical diameter of ball20
Height of spine above floor of neural canal48
11.Length of centrum to rim of ball41
Vertical diameter of ball22
Extent of articular surface of transverse process16
Width of spine32
15.Length of centrum to rim of ball41
Transverse diameter of ball21
Vertical diameter of ball24
20.Length of centrum to rim of ball42
Vertical diameter of ball25
Height of spine above floor of neural canal58
24.Length to rim of ball41
Transverse diameter of ball22
Vertical diameter of ball23
Height of spine49
28.Length to rim of ball40
Vertical diameter of ball24
Transverse diameter of ball23
Height of spine54
32.Length to rim of ball38
Vertical diameter of ball25
Transverse diameter of ball24
35.Length to rim of ball37

Caudal vertebrae.

Immediately following the thirty-fifth rib-bearing vertebra there is an abrupt change, the tubercular process for the rib giving place to an elongated transverse process. From the position of the pelvis, it is evident that the ilia were attached to the first pair of these. Precisely this relation of pelvis to the vertebrae is found in such lizards as the Monitor and Iguana, and it is probable that such is the relation in all the Pythonomorpha. It will thus be seen that there are no distinctively lumbar vertebrae, if by such are meant free, non-costiferous, pre-sacral vertebrae. The vertebrae of these animals that have been so designated by writers are in reality basal caudal. A distinctive term for them—those with transverse, non-costiferous processes and without chevrons—is needed, and we propose, provisionally, the term pygial. There are seven in the present series, all characterized by elongated transverse processes, and not differing much from each other. The vertebrae lie in the matrix with the ventral aspect uppermost, concealing the spine and upper parts. The under surface is somewhat flattened, and, as in the preceding vertebrae, is gently concave antero-posteriorly. The transverse processes are elongate, stout towards the base, apparently all of nearly equal length, and directed gently backwards and downwards. In the anterior vertebrae the processes spring from near the front part: as the centra become shorter they arise from near the middle. In the last one of the series there are minute indications of chevrons.

MEASUREMENTS OF THE PYGIAL CAUDAL VERTEBRAE.

1. Length to rim of ball 36 millim.
Width of ball 25
Expanse of transverse processes130
Width of transverse process near base   17
2.Length to rim of ball 33
3.Length to rim of ball 31
4.Length to rim of ball 29
5.Length to rim of ball 28
6.Length to rim of ball 27
Expanse of transverse processes130
Width of ball 24
7.Length to rim of ball 27

The centra of those caudal vertebrae which have chevrons do not differ much in shape. They become less constricted, and, back of the middle of the series, are smoothly cylindrical in shape. The transverse processes decrease gradually in length, disappearing entirely in the twenty-fifth or twenty-sixth. The spinous processes are more or less incompletely preserved in the anterior vertebrae. They increase only gradually in length for the first twenty of the series, and are markedly oblique, with the posterior border stout, and the anterior border alate. With the twenty-sixth they begin to increase more rapidly in length, and have become more nearly vertical in position, and are thinner at each margin. In the thirty-fifth or thirty-sixth they attain their greatest length, and are here directed slightly forwards. Thence to the end of the tail, the length decreases gradually, and, in position, they are directed more and more obliquely backward. The chevrons are strongly oblique throughout the series and are firmly co-ossified with the centrum.

The tail, it is thus seen, has a broad, vertical, fin-like extremity, which, doubtless, aided much in the propulsion of the animal through the water.

There are sixty-seven vertebrae with chevrons present in the specimen, all continuous, except in one place. The last one is less than one-fourth of an inch in diameter, and shows that there had been yet another, possibly several more. Toward the base of the series the tail has been bent forwards over the back, and it is possible that, where the break occurs, there has been a vertebra lost. The measurements, however, do not seem to indicate any loss. The entire series of vertebrae was not less than sixty-eight, and probably not more than seventy, making for the entire vertebral series one hundred and seventeen to twenty.

MEASUREMENTS OF THE CHEVRON-BEARING CAUDAL VERTEBRAE.