D. M. 8. Watson—Eugyrinus wild. 13 
horizons in the Rothhegende. Thus Hylonomous wildi cannot be 
referred to its original Microsaurian genus, and as it does not fall 
into any described Branchiosaur genus I propose for it the name 
HLugyrinus. 
The skull of Hugyrinus is by far the best-preserved Branchiosaur 
skull known, and is much more primitive in its structure than that 
of the well-known Permian and Stephanian genera. It differs from 
Branchiosaurus in being much longer and narrower, and in having 
very much smaller orbits; it is, in fact, more like the central type of 
Labyrinthodont skull represented by Hryops. 
In consequence of its smaller orbits, it retains a lachrymal, and 
has postfrontal, postorbital, jugal, and squamosal bones much 
more resembling the ordinary Labyrinthodont type than those of 
Branchiosaurus. The palate of Hugyrinus differs from that of 
Branchiosaurus in the narrower hinder part of the parasphenoid, 
which in it can by no stretch of the imagination be called T-shaped ; 
and in the much smaller interpterygoid varieties and larger pterygoids 
which go with them. These differences are exactly those which 
separate such a Rachitomous amphibian as Dwinasaurus from its 
Stereospondylous descendant, Plagiosaurus, and go to show that 
the trend of evolution in Phyllospondyli is the same as that in 
Labyrinthodonta. HEugyrinus agrees in stage with an Upper 
Permian Labyrinthodont, Branchiosaurus with one from the Upper 
Trias. 
The skull of Hugyrinus is very valuable, because it shows that the 
general structure of the early Phyllospondylian skull is identical in 
essentials with that of the Labyrinthodonta. In comparison with 
Branchiosaurus it shows that the Phyllospondyli had a similar 
evolutionary history to that of the Labyrinthodonta, carried through 
at a much earlier date, and of which only the latter half is known. 
As the latter parts of the stories of the two groups are similar we 
are surely justified in expecting that the beginnings will resemble 
one another, and that we may take the primitive Labyrinthodonts 
as representing structurally the unknown ancestors of the 
Branchiosauria. 
Thus the known Phyllospondyli can in no sense be regarded as 
prunitive amphibia; they represent the later members of a side-line 
which underwent a precocious and very rapid evolution. 
Eugyrinus is of geological importance, because it adds another 
link to the chain of evidence which proves that North America 
and Britain formed a single zoological province in Upper 
Carboniferous times. The resemblance between the vertebrate 
fauna of the North American Coal-measures and that of Britain is 
very great. Several species of fish, a number of genera of fish and 
amphibia, and nearly all the definitely determinable families of 
vertebrates occur on both sides of the Atlantic. The flora is, of 
course, equally similar. 
The resemblances are, in fact, so great as only to be explicable 
