CHAPTER, tit 
THE POSSIBLE FORERUNNERS OF THE MAMMALIA 
THE relationship of Mammals to Vertebrates lymg below them 
in the scale, their origin in fact, is a much-debated question, 
with many attempted solutions. To enter into this large 
question in detail would involve a great deal of useless state- 
ment of arguments founded upon misleading or upon quite in- 
accurate “facts.” It will perhaps be sufficient if we reflect here 
the current view most in vogue at the present, ze. that which 
would refer the Mammalia to reptiles belonging to the extinct 
Permian and Triassic group of the Theromorpha (also called 
Anomodontia). These have been explored lately to a very large 
extent, and chiefly by Professor Seeley." The very fact that a 
genus Tritylodon, only known by the forepart of the skull, has 
been called Mammalian and Anomodont by various authors, 
shows at least the difficulty of differentiating the two groups when 
the material for study is imperfect. As a matter of fact 
these Theromorpha are without doubt reptiles; they show, for 
example, a lower jaw formed out of several distinct pieces, of 
which the articular articulates with a fixed quadrate on the 
skull. They possess the characteristic reptilian bones, the 
“transverse, the pre- and post-frontals, and there are various 
other points of structure which leave no room for doubt as to 
their truly reptilian nature. There are, however, numerous 
indications of an evolution in the mammalian direction in all 
parts of the skeleton, to the more important of which some 
reference will be made here. It may be as well to clear the 
1 A series of papers in the Phil. Trans. for 1888-96, of which a useful abstract 
by Professor Osborn was published in the American Naturalist, 1898, p. 309; see 
also Cambr. Nat. Hist. viti. 1901, p. 303. 
