The Skull of Labidosaurus. S38 
doubt upon the homologies of the two pairs of bones on the posterior 
border, the squamosal and quadrato-jugal of Dimetrodon, the epiotics 
and quadrato-jugal of Hdaphosaurus, the postparietals and epiotics 
of Labidosaurus. EHdaphosaurus has a temporal vacuity situated 
much higher than in Dimetrodon, by the sides of the parietal bones. 
Case believes that there is also another vacuity below, separated by 
a bar from the upper one. No certain evidence of such a vacuity 
is yet forthcoming, and I shall doubt its presence until demonstrated. 
I cannot believe that the presence of vacuities in the temporal region 
of these early reptiles is of the great taxonomic importance that 
has been ascribed to them. 
Perhaps nothing is more noticeable in the skull of the present 
reptile than the small comparative size of the brain cavity. While 
the skull measures over seven inches in length and five in width, the 
foramen magnum is of almost precisely the same size and shape as that 
of a small Amblyrhynchus lizard whose skull measures but sixty 
millimeters in length. Not only is the foramen of the same size, 
but the brain cavity also is only a trifle larger in Labidosaurus. 
Small brain capacity is of course to be expected in this old reptile, 
and, moreover, the size of the brain cavity as compared with that 
of the skull, may not be a fair criterion of the relative intelligence 
of the two animals. Nevertheless, that their intelligence was rela- 
tively much lower than that of the existing lizards cannot be doubted. 
As to the habits of Labidosawrus and its allies, the pariotichids, 
one can hardly doubt that the most of them at least were shore 
dwellers. The form described by me as Pariotichus laticeps,° is 
essentially identical in skeletal and skull structure with Labido- 
saurus, so far as can be determined. Indeed it is not impossible 
that the form may be a real Labidosaurus of a small species. Many 
of the species of Pariotichus, like Labidosaurus hamatus, had the 
peculiarly elongated premaxillary teeth, though perhaps never so 
exaggerated as in the present species. The only use that I can con- 
ceive for such teeth was the seizure of small creatures from burrows, 
holes or crevices, or for detaching such as may have been closely 
adherent to rocks. The maxillary and mandibular teeth were not 
at all pointed, but were, rather more sectorial than prehensile. 
"Biological Bulletin, vol. xvii, p. 241, 1909. 
