MARINE REPTILES 221 



MARINE REPTILES 

 BY JOHN C. MERRIAM 



During the past ten 3^ears important additions to our knowledge of all 

 the great groups of marine reptiles have been made, but in certain of 

 them, as the mosasaurs, which had received especial consideration during 

 the preceding decade, this advance was relatively small. 



The contributions which have added most to our knowledge of special' 

 groups would seem to the writer to be : 



1. The full description and interpretation of the thalattosuchian 

 crocodiles. 



2. The additions to our knowledge of the skeletal structure, habits, 

 and relationships of the plesiosaurs. 



3. The description and interpretation of the structure of the Triassic, 

 late Jurassic, and Cretaceous ichthyosaurs. 



4. The description of a typically marine group of rhynchocephalian 

 or diaptosaurian reptiles. 



Of much interest are also the studies of the marine turtles, Archelon 

 and Protostega, initiated just before the beginning of the past decade; 

 the monographic revision of the marine turtles of America; the discus- 

 sion of the structure, habits and origin of the mosasaurs ; and the descrip- 

 tion of a new marine reptilian type, the omphalosaurs, which does not as 

 yet seem to find a clearly defined place in our classification scheme of the 

 Reptilia. 



Important collections representing marine reptiles have been brought 

 together by many institutions during the past decade, but the value of 

 this material in advancing our knowledge will in many cases not be 

 determined until the completion of studies now in progress. Of the 

 collections which are known to the writer especial importance seems to 

 attach to the splendid plesiosaur and ichthyosaur material from the 

 Oxford Clay which has become the property of the British Museum ; the 

 complete plesiosaur specimens obtained from Holzmaden by the Royal 

 Museum of Stuttgart; the extraordinary American plesiosaur material 

 acquired by the University of Kansas ; the Baptanodon specimens, w^hich 

 have been obtained from the American Jurassic by the University of "Wyo- 

 ming, the Carnegie Museum, and the American Museum; the splendid 

 American mosasaur specimens acquired by the American Museum, the 

 University of Chicago, and the Geological Institute of Tubingen; the 

 collections of ichthyosaur material from the Cretaceous of Germany 

 obtained by the University of Munich; the Triassic ichthyosaur coUec- 



