CRETACEOUS REPTILES. 395 
traces of the persistent cup-and-ball articulation between them remain. In the 
Scincoids the bodies of the sacral vertebrae become anchylosed together. The 
extremities of the sacral pleurapophyses come into contact in the Dolichosaurus, 
but do not coalesce: the second sacral vertebra presents a ball to the first caudal, 
as in existing Lacertians, not a cup, as in the modern Crocodilia. On the right 
side of the specimen the hinder half of the ihac bone extends backwards, pro- 
jecting freely a short way behind the second sacral pleurapophysis, as in some 
modern Lacertians (Cyclodus, e.g.). On the left side a part of the ilium is 
preserved, which extends to the acetabulum. A portion of the expanded ischium 
is likewise preserved, and the distal half of the left femur extends back in a right 
line from the position of the hip-joint. ‘The length of the entire femur could not 
have exceeded three centimeters (14 lines) ; it thus agrees in its relative shortness 
with the humerus in Pl. XXXVIII. fig. 1, 53, and accords with the idea that the 
Dolichosaurus was more aquatic in its habits than the modern Lacertians, most 
of which have longer proportional humeri and femora. The femur of the Doli- 
chosaurus had a medullary cavity. The under surface of the first two caudal 
vertebre is impressed by a median, longitudinal, shallow canal, bounded by two 
slight ridges, diverging posteriorly in the second caudal to the tubercles that 
have supported the hzmal arch ; these tubercles are close to the posterior arti- 
culation. A part of the spine of this hamal arch is preserved nearly in its true 
position. 
The foregoing comparisons show that all the general characters of the Lacertian 
type of the vertebrate skeleton are presented by the Dolichosaurus: they are 
most modified in the cervical region, where the Ophidian type is rather followed, 
in the number and size of the vertebrz, and in the size and shape of the ribs: 
a less decided approach, but one still indicating an affinity to the Ophidians, is 
made by the unusual length of the slender trunk, which includes, from the skull 
to the sacrum, not fewer than fifty-seven vertebre, and is not less than eighteen 
inches in length. The smallness of the head accords with the long and slender 
proportions of the neck, and must have added to the snake-like appearance of 
this early example of proccelian lizard. But the complete and typically Lacer- 
tian organization of the scapular and pelvic arches, and of their locomotive 
appendages, proves that the Dolichosaurus was more strictly a lacertine Saurian 
than the existing genera, Pseudopus, Bipes and Ophisaurus, which eftect the 
transition from the Lizards to the Snakes, or typical Ophidian reptiles. 
