838 General Notes. 
The prootic is a small flat elliptical bone, connected with 
base of the skull, the supraoccipital, and the opisthotic. Th 
structure of the bones shows that there must have been & 
veloped large masses of cartilage, still more than in young se 
turtles, connecting these bones. ‘ £ 
Between the basioccipital and the quadrate a strong handi 
like bone is expanded, fitting in a grove of the quadrate. 
is the stapes, as Professor Cope correctly suggested, exactly it 
the same position as in Sphenodon, in which it is of similar shape 
but not so stout. 
Turning now to the upper part of the skull, we find the part 
tal bones of exactly the same structure as in Sphenodon, and i 
front of those the very small frontals. : gi 
The parietal foramen, which is very large, as in Sphenodon 8 
situated between the frontals and parietals or in the frontals, i4 
similar way as in Sphenodon. In the upper part of the Spat 
don skull the parietal foramen is formed entirely by the j 
in the lower part by both the parietals and frontals. The m 
in Ichthyosaurus are very large bones, touching the froni 
parietals, postfrontals, prefrontals, lachrymals, and pren axillaris 
We have now to consider that part of the skull situated D 
tween the supratemporal fossa, the orbits, and the quadrate. l 
The supratemporal fossa is formed by three bones Bpo 
etal, the postfrontal, and a big bone forming its posterior fi 
exterior border. This bone, which is connected also with 
quadrate and another bone which joins the quadrate, quay 
jugal, postorbital, and postfrontal, is the supratemporal 
Lacertilia, which is united in Sphenodon to the squamosal- Si 
This bone is called mastoid by Owen, squamosal by Seeley a = 
ai 
et 
$ 
The place which is taken in Ichthyosaurus by the sup 
by os 
don. o hyosal 
_ The lachrymal is free from the prefrontal in Icht 
in many nes it is united with that bone $ ized ft 
ithe vertebrae of Ichthyosaurus are only Speci | ter 
Sphenodon-like form in which the notochordal charac 
