146 WATER REPTILES OF THE PAST AND PRESENT 



lies in the elongation of the neck, quite like that of the wholly 

 unrelated nothosaurs and proganosaurs, which have been described 

 in the foregoing pages. Doubtless similar habits in each had like 

 results, but just what these habits were in the slender lizards we 

 do not yet know. 



Aigialosaurs. — Within recent years a number of other lizards 

 have been made known from the Lower Cretaceous rocks of Dal- 

 matia which present most remarkable intermediate characters 

 between the monitors, dolichosaurs, and the mosasaurs, the famous 

 sea-lizards of Upper Cretaceous age. Some of these lizards had 

 twelve or thirteen vertebrae in the neck, while others had but 

 seven — an unusually short neck characteristic of the mosasaurs. 

 These latter kinds, belonging to two or three genera, are included 

 in a distinct group. They were long and slender, the head 

 long and pointed. The teeth, conical and sharp, were attached 

 in shallow pits, quite as in the mosasaurs. The lower jaws had a 

 hinge just back of the teeth, as in the mosasaurs, of which the only 

 trace in modern lizards is found among the monitors. Still more 

 remarkable, though perhaps not so easily appreciated, is the shape 

 of the quadrate bone, with a broad flaring rim for the ear cavity, 

 quite unlike that of land lizards, but quite like that of the mosa- 

 saurs. In fact, the very peculiar skull is almost identical with that 

 of the true sea-lizards. The body and tail also resemble those of 

 the mosasaurs more than those of the monitors, but there is a 

 firm attachment of the pelvis to the backbone, and the legs are 

 long and lizard-like, though not as long as those of land lizards. 

 The feet were webbed in life, and the toes have no claws, conclu- 

 sively demonstrating their water habits. The vertebrae indeed 

 have the same peculiar articulations, called zygosphenes, as in 

 most of the mosasaurs. The largest aigialosaurs were about six 

 feet in length, that is, of about the size of the smallest known 

 mosasaurs. 



We have then in the aigialosaurs nearly every known inter- 

 mediate character that we could wish for in a connecting link 

 between the mosasaurs and the monitors, lizards that were equally 

 at home on land or in the water, and there can be scarcely a doubt 

 that they were either the direct ancestors or closely akin to the 



