SCIENCE. 



295 



Subclass SYNAPSIDA Osborn 1903. Order 

 Cotylosauria Cope 1880 (Pareiasauria See- 

 ley 1889). 



Superorder ANOMODONTIA Owen 1800. (Ther- 

 omorpha Cope 1878, in part.) 

 C Order Theriodontia Owen 1870. Suborder 

 Therocephalia Broom 1903. 

 Suborder Cynodontia Owen 1801. 

 Order Dicynodontia Owen 1800. 

 Order Placode ntia auct. ex H. von Meyer 



1803 Incertge Sedis. 

 Order Sauropterygia Owen 1800. Suborder 

 Simosauria auct. ex Gervais 1845. 



(Nothosauria Seeley 1882.) 

 Suborder Plesiosauria auct. ex Quenstedt 

 1852. 



Order Testudinata auct. ex Shaw 1802. 

 Suborder Pleurodira auct. ex Dumeril and 



Bibron 1835. 

 Suborder Cryptodira auct. ex Dumeril and 



Bibron 1835. 

 Suborder Trionychia auct. ex Pictet 1853. 



ichthyosaurs the long tail is correlated with 

 short propodials. In both plesiosaurs and 

 turtles the ilimn is directed downward and 

 forward, in correlation with the backward 

 thrust of the paddles ; in both, the scapula 

 acquires secondarily a proscapular process. 

 The fundamental characters distin^ishing 

 the two groups may be summarized in the 

 table given below. 



Continuing the discussion. Dr. J. H. 

 McGregor maintained and expanded his 

 previous argument for the derivation of 

 the Ichthyosauria from the Diapsida, and 



Subclass DIAPSIDA Osborn 1903. 

 Superorder DIAPTOSAURIA Osborn 1903. 

 Order Procolophonia Seeley 1807. 

 Order Protorosauria Seeley 1887. 

 Order Proganosauria Baur 1887. 

 Order Gnathodontia Owen 1080. 



(Rhynchosauria Osborn 1903). 

 Order Pelycosauria Cope 1878. 

 Order Choristodera Cope 1877. 

 Order Rhynchocephalia Giinther 1808. 

 Order Parasuchia Huxley 1875. 



Suborder Aetosauria Nicholson and Lydek- 

 ker 1889. 



Suborder Phytosaiiria Baur 1894 ex 

 Jaeger 1828. 

 Order Ichthyosauria Blainville 1835 ex 

 Jaeger 1824. 



( Ichthyopterygia Owen 1800.) 

 Order Crocodilia Wagler (?) 1830. 

 Suborder Mesosuchia Huxley 1875. 

 Suborder Eusuchia Huxley 1875. 

 Suborder Thalattosuchia Fraas 1901. 

 Superorder DINOSAURIA Owen 1840. 

 Order Theropoda Marsh 1881. 



Suborder Megalosauria ex Fitzinger 1843. 



(Thecodontia Owen 1800.) 

 Suborder Symphypoda Cope 1807. 

 ( Compsognatha Huxley 1870.) 

 Order Opisthoccelia Owen 1800. 



(Sauropoda Marsh 1881.) 

 Order Orthopoda Cope ISGO. 

 (Predentata Marsh 1894.) 

 Superorder SQUAMATA Oppel 1811. 

 f Order Lacertilia Owen 1839. 

 -I Order Mosasauria auct. ex Gervais 1845. 

 ( Order Ophidia Brogniart 1802. 

 Order Pterosauria auct. ex Kaup 1834. 



for the probably secondary nature of the 

 closed condition of the temporal arch region 

 of the skull. 



Turtles. 



Plesiosaurs. 



Vomer (parasphenoid) un- 



Paired prevomers. 



paired. 



A separate parasphenoid. 



No posterior parasphenoid 



process. 



Opisthotic not separate. 



Opisthotic separate 



Cervicals eight. 



Cervicals 13-7r.. 



Ribs intercentral in attach- 



Ribsdiapophysial in attach- 



ment. 



ment. 



Ten dorsals. 



Twenty dorsals. 



Dr. 0. P. Hay pointed out the now con- 

 vincing evidence that the original Testudi- 

 nata had a closed, or solid, temporal roof 



