SEHA-SERPENTS. 139 
been of the greatest service in completing our knowledge of this 
strange group of saurians. In the American Cretaceous seas 
they ruled supreme, as their numbers, size, and carnivorous habits 
enabled them easily to vanquish all rivals. Probably some of 
them were seventy-five feet in length, the smallest being ten or 
twelve feet long. In the inland Cretaceous sea from which the 
Rocky Mountains were beginning to emerge, these ancient sea- 
serpents abounded; and many were entombed in its muddy 
deposits. On one occasion, as Professor Marsh rode through a 
valley washed out of this old ocean bed, he observed no less than 
seven different skeletons of these monsters in sight at once! 
The same authority mentions that the Museum of Yale Coilege 
contains remains of not less than 1400 distinct individuals. In 
some of these the skeleton is nearly if not quite complete; so 
that every part of its structure can be determined with almost 
absolute certainty. | 
According to Professor Cope of Pennsylvania University, who 
has made a special study of this group of extinct saurians, fifty- 
one species have been discovered in North America, in the States 
of New Jersey, Alabama, Kansas, North Carolina, Mississippi, 
and Nebraska. The same authority has shown that they were 
characterised by a wonderful elongation of form, especially of the 
tail; that their heads were large, flat, and conical in shape, with 
eyes directed partly upward ; that they were furnished with two 
pairs of paddles like the flippers of a whale. With these flippers, 
and the eel-like strokes of their flattened tail, they swam with 
considerable speed. Like snakes, they were furnished with four 
rows of formidable teeth on the roof of the mouth, which served 
admirably for seizing their prey. 
But the most remarkable feature in these creatures was the 
arrangement for permitting them to swallow their prey whole, in 
the manner of snakes. Thus each half of the lower jaw was 
articulated at a point nearly midway between the ear and the 
chin, so as to greatly widen the space between the jaws, and 
