310 THE AMERICAN NATURALIST. (VoL XXXII. 
phodontia and Cynodontia. Allied to the Proganosauria, more- 
over, are such widely diverse types as Palzohatteria, Protoro- 
saurus, and Kadaliosaurus. 
The origin of the Mammalia is enshrouded in still more 
doubt. Without the aid of paleontology, Huxley, in 1880, 
related his Hypotheria, or oldest types of mammals, to the 
ancient Amphibia. 
In the writer’s full notes upon Professor Huxley’s lectures delivered in 
his course of 1879-80 occurs the following sentence: “ When we find a form 
that bridges over this gap (that is, between lower vertebrates and mammals) 
it will in all probability have a double condyle caused by a reduction of the 
basioccipital and increase of the exoccipital parts. The quadrate will have 
begun to diminish and the squamosal to enlarge, coming into relation with 
the angular and surangular. That this promammal will be discovered when 
e immense number of reptilian remains from the older rocks are studied 
I myself have little doubt.” This the writer regards as a more successful 
forecast than that published by Huxley a year later. At this time he was 
evidently thinking over his now famous paper of Dec. 14, 1880,! in which 
occurs the following paragraph: “ Our existing classification has no place for 
this submammalian stage of evolution (already indicated by Haeckel under 
the name of Promammale). It would be separated from the Sauropsida by 
its two condyles, and by the retention of the left as the principal aortic arch; 
while it would probably be no less differentiate from the Amphibia by the 
presence of the amnion and the absence of branchiz in any period of life. 
I propose to term the representatives of this stage Hypotheria; and I do not 
doubt that when we have a fuller knowledge of the terrestrial vertebrata of 
the later Palaeozoic epochs, forms belonging to this stage will be found 
among them... . us I regard the amphibian type as a representative 
of the next lower stage of vertebrate evolution. From the Hypotheria, as 
schematically shown on page 659, in which the mandible articulates with 
the quadrate, were derived the Prototheria, in which the large free malleus 
takes the place of the quadrate; from this type sprang the Metatheria, and 
from these, in turn, the Eutheria.” 
It is clearly implied by Huxley that the promammal had the paired 
occipital condyle of the ancient Amphibia, an assumption of great 
morphological importance, and differing from that expressed in his earlier 
lecture quoted above. He also, in his preconception of the homology of the 
quadrate with the malleus, lightly passes over the difficulty of freeing the 
quadrate from the squamosal, to which it is closely joined in all the Amphibia. 
In brief, this brilliant paper lacks the author’s usual unsparing logic. 
1 On the Application of the Laws of Evolution to the Arrangement of the 
Vertebrata, and More Particularly of the Mammalia. Proc. Zool. Soc. of London, 
Dec. 4, 1880, p. 659. 
