568.1 48 [January 



VI 

 The Structure and Habits of the Plesiosauria.^ 



SINCE the discovery of the Plesiosauria and the determination of 

 their characters, which are so completely different from those of 

 all the existing reptiles, palaeontologists engaged in studying them 

 have often attempted to reconstruct them in their outward form and 

 natural surroundings, or, so to speak, to bring them back to life. 

 Conybeare, the describer of Plcsiosaurus dolichodeirus, which was 

 first found in the form of complete skeletons, quite rightly 

 determined its position among the reptiles, its aquatic habits, and 

 its character as a beast of prey. The diagrammatic sketch of the 

 skeleton given by him also avoids an error which was afterwards 

 repeated and continually exaggerated, since it represents the neck 

 not bent like that of a swan, but only gently curved as a whole. 

 Nevertheless, he states in the text, that he also ascribes to the neck 

 great flexibility and the power of snatching prey, and recognises in 

 the first character a compensation for the want of a large mouth, 

 with powerful jaws and strong teeth, such as the Ichthyosauria 

 possess. He represented the Plesiosaurus as a creature lying in 

 wait for prey in the sea-weed in the shallower parts of the sea near 

 the shore, the body under the water, the nostrils projecting from it 

 for breathing. While a more sluggish mode of life was thus postu- 

 lated, other workers ascribed to the Plesiosauria a quick restless 

 movement on the surface of the sea, either in the neighbourhood of 

 the coast between the rocks or in the open sea, rapidly darting the 

 long flexible neck and the small head to obtain food. Restorations 

 which illustrate this view, accepted, among others, by T. C. Winkler, 

 Hutchinson, and Koken, are to be found in the works of the two first- 

 mentioned authors, and are based on the assumption of an easily 

 moveable swan-like neck, sharply separated from the barrel-shaped 

 body. This idea was, indeed, carried to such an extreme that 

 Plesiosaurus was compared to a snake drawn through the shell of a 

 tortoise, giving rise also to the idea of a head standing out at an 

 angle from the vertebral column of the neck like that of a bird. 

 From a possibly more careful examination of the separate parts 



' Translation of the final chapter of a memoir on the Plesiosam'ia of the South German 

 Lias Formation in Abhandl. k. preuss. Akad. Wiss., Berlin, 1895, pp. 75-80. Revised 

 by the Author, 1897. The illustration (Plate III.) kindly lent by the Berlin Academy. 



