320 GEOLOGICAL SUEVEY OF THE TEERITORIES. 



tlie coast line extended from Arkansas to near Fort Eiley, on the Kan- 

 sas Kiver, and passing a little eastward traversed Minnesota to the 

 British possessions, near the head of Lake Superior. The extent of sea 

 to the westward was vast, and geology has not yet laid down its bound- 

 ary ; it was probably a shore now submerged beneath the waters of the 

 North Pacific Ocean. 



Far out on its expanse might have been seen in those ancient days, 

 a huge, snake-like form which rose above the surface and stood erect, 

 with tapering throat and arrow-shaped head ; or swayed about, describ- 

 ing a circle of twenty feet radius above the water.* Then it would dive 

 into the depths, and naught would be visible but the foam caused by 

 the disappearing mass of life. Should several have appeared together, 

 we can easily imagine tall, twining forms rising to the height of the 

 masts of a fishing fleet, or like snakes twisting and knotting themselves 

 together. This extraordinary neck — for such it was — rose from a body 

 of elephantine proportions ; and a tail of the serpent-pattern balanced 

 it behind. The limbs were probably two pairs of paddles like those of 

 Plesiosaums, from which this diver chiefly differed in the arrangement 

 of the bones of the breast. In the best known species 22 feet repre- 

 sent the neck in a total length of 50 feet. 



This is the Masmosaurus jplatyurus, Cope, a carnivorous sea-reptile, 

 no doubt adapted for deeper waters than many of the others. Like 

 the snake-bird of Florida, it probably often swam many feet below the 

 surface, raising the head to the distant air for a breath, then withdraw- 

 ing it and exploring the depths 40 feet below, without altering the posi- 

 tion of its body. From the localities in which the bones have been 

 found in Kansas, it must have wandered far from land, and that many 

 kinds of fishes formed its food is shown by the teeth and scales found 

 in the position of its stomach. 



A second species of somewhat similar character and habits differed 

 very much in some points of structure. The neck was drawn out to a 

 wonderful degree of attenuation, while the tail was relatively very 

 Stout, more so, indeed, than in the Elasmosaurus, as though to balance 

 the anterior regions while occupied in various actions ; e. g., while cap- 

 turing its food. This was a powerful swimmer, its paddles measuring 

 four feet in length, with an expanse therefore of about eleven feet. It 

 is known as Polycotylus latipinnis, Cope. 



The two species just described formed a small representation in our 

 great interior sea, of an order which swarmed, at the same time or near 

 it, over the gulfs and bays of old Europe. There they abounded twenty 

 to one. Perhaps one reason for this was the almost entire absence of 

 the real rulers of the waters of ancient America, viz, the PytJionomorphs. 

 These sea-serpents — for such they were — embrace more than half the 

 species found in the limestone rocks in Kansas, and abound in those of 

 New Jersey and Alabama. Only four have been seen as yet in Europe. 



Eesearches into their structure have shown that they were of wonder- 

 ful elongation of form, especially of tail. That their heads were large, 

 flat, and conic, with eyes directed partly upward ; that they were fur- 

 nished with two x)airs of paddles like the flippers of a whale, but with 

 short or no portion representing the arm. With these flippers and the 

 eel-like strokes of their flattened tail they swam, some with less others 

 with greater speed. They were furnished, like snakes, with four rows of 

 formidable teeth on the roof of the mouth. Though these were not 

 designed for mastication, and, without paws for grasping, could have 

 been little used for cutting, as weapons for seizing their prey they were 

 very formidable. And here we have to consider a peculiarity of these 



