222 TEN years' progress in vertebrate paleontology 



tions from Spitzbergen secured by the Geological Institute of Upsala; 

 and the collections of Triassic ichthvosaurian, thallatosaurian, and om- 

 phalosaurian remains assembled from California and Xevada by the 

 University of California. 



During the past decade the following problems relating to the marine 

 Eeptilia have been subjects for general discussion : 



1. Adaptation and affinities of the Thalattosuchia — Now known to be 

 typical aquatic forms, but not entirely limited to high seas. 



2. Eelation of Pasasuchia to true Crocodilia — Pasasuchians separated 

 as a distinct order. 



3. Origin of the Mosasauria and habitat of young forms — Views as 

 to derivation from a Yaranus-like form of Lower Cretaceous age more 

 fully expressed than previously. General absence of specimens repre- 

 senting young suggest that they possibly lived in fresh water. 



4. Eelationships of the order Ichthyosauria — Suggestions as to rela- 

 tionship to Eh}mchocephalia, to Pasachusia, to Cotylosauria, and to 

 Proganosauria. View that the ichthyosaurs originally had a lateral 

 temporal fenestra seems not supported by evidence of the Middle Triassic 

 forms. Xo clearly defined theory as to origin of this group has been 

 worked out. Probably an old order near Cotylosauria, and has many 

 points in common with the proganosaurs. 



5. The origin and course of evolution of the marine turtles, and 

 particularly the course of evolution of the Eecent Dermochelyidse. — Ex- 

 tremely varied opinions as to origin of the leatherback turtles have been 

 expressed. The questions involved have a ven^ important relation to 

 the problem of origin and evolution of the Testudinata. 



Of the numerous lines of investigation in the study of marine reptiles 

 now open to us, the following seem to promise important results : 



1. A thorough search in all known marine deposits of Lower Triassic 

 age for ancestral forms of the ichthyosaurs and omphalosaurs. 



2. Extensive search for marine reptilian remains in the Middle and 

 Upper Triassic of Europe, coupled with an exhaustive comparative study 

 of the collections of marine Triassic forms in all of the European 

 museums. 



3. Exploration of marine Mesozoic formations in Asia, with special 

 reference to obtaining material representing early forms of the Ichthy- 

 osauria, Plesiosauria, and Mosasauria. 



4. An exhaustive examination of the evidence obtained from a study 

 of the history of marine Eeptilia with particular reference to its bearing 

 upon the problem of cause and process in evolution. 



In a study of the marine reptiles we are necessarily concerned with 



