ANOMALOUS REPTILES 117 
or knob-like process, instead of by two, as in the Labyrinthodonts 
and all the amphibia. 
Paleontologists have concluded that Labyrinthodonts, Anomo- 
donts, and Monotreme mammals are all descended from some 
common amphibian stock. If this theory is true, the Anomodonts 
retained, while they were yet in existence, structures showing a 
relationship with mammals or a foreshadowing of them, which in 
all other reptiles have been altogether lost. 
Paleontologists are often greatly helped in their studies by 
comparing extinct types of life with some of the living types which 
are very old-fashioned and, one would think, ought to have become 
extinct ages ago, but fortunately have not! We mentioned just 
now the Tuatara, as a case in point; another still more important 
case is that of the Monotreme mammals—the curious Duckbill 
and the Spiny Ant-eater (Echidna) of Australia (which, of course, 
is not one of the true Ant-eaters). These two remarkable egg- 
laying mammals show some wonderful points of resemblance to 
the Anomodonts—points which cannot, however, be explained 
without entering too much into dry details of Anatomy. Indeed, 
they are a great puzzle to naturalists, and one hardly knows 
whether we ought to call them reptiles or mammals; but since 
they do suckle their young ones (after a primitive fashion, though), 
they have been placed with the latter; still it requires a slight 
stretch of imagination to look upon an egg-laying creature as a 
mammal. 
Leaving now the Anomodonts, we pass on to consider another 
order—the Proterosauria. In America and France the subject 
has been studied by Professors Cope’ and Gaudry. The former 
palzontologist has described, amongst others, such remarkable 
1 History of the Vertebrata of the Permian Formation of Texas, by Professor 
E. D. Cope, Pal. Bull, No. 32. 
