TJIK STHUOTUBE AND CLASSIHCATIOX. 
] M8 
wl! " vtv'rarew'— !or»lK,w^ »f 
times. \ en eaic somewhat unspecialized 
r ^.n.rd to the excessive number of teeth. In the greatly extended field of ex- 
Iltion we should have anticipated finding one or more types of dentrt.on wholly d.s- 
!inct from those described by Professor Owen from the English Jurasmc but this has 
not proved to he the ease. Fmm the very fact of their general zoological relationship, _ 
howlver, these newly-discovered genera from other countries are of “ 
their taring upon the structure and relationships of the English genera. It is not so 
much then the form of the teeth as the presence of an excessive number of molars, 
which f?ives a primitive character to the Jurassic fauna. In other respects it is, upon 
Fioi-re 1. The types of the British rae.sozoic mammals, representing the natural size. 1. Amphilesles. 
2. AmphUyltu. 3. PhuKColotheriuiii. 4. Triconodon mordcuc. 6. Peramns. 7. Spalacotherium. 8. PeraUstes. 9. 
PmupcJax. \Q. LfjtUx'ladut. U. Amblolherium. 12. Phascolestes. 13. Achtjrodon. lA. Stylodon. 13. Athrodon. 
10. liolodnn. 18. Plnyiaulax minor. 19. Stereognathus. 
the wliolc, surprisin<rly modern. The various divisions of the dental series are almost 
ns sharply defined as in modern genera. Another characteristic is the diminutive size 
of tliis fauna. As shown in the accompanying series of life-size outlines of the man- 
dibular and maxillary specimens, the genera vary from the size of the smallest 
Ilodents to that of the smaller varieties of the Hedgehog. 
Literature. Professor Owen gave in his Memoir a full list of the papers upon 
the Mesozoic Mammalia which had appeared previously. The most valuable among 
the.sc were his own contributions upon the Stonesfield Slate genera in the “ Transac- 
tions of the (icological Society, 1835”, and Dr. Falconer’s Memoirs upon Plagiaulax 
in the “ (Quarterly Journal of the Geological Society,” in 1857 and 1862. Professor 
Owen s well known Memoir of 1871, embraced a very elaborate and able description 
and discussion of all the Mesozoic genera which were then known. In 1878 Profes- 
sor Marsh first discovered the American Jurassic mammals, and began a series of brief 
