402 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
with the quadratojugal and covers the dorsal external surface of the 
quadrate (figs. H and I). Lateral and ventral to the squamosal and 
lying upon the lower external surface of the quadrate is the quadrato- 
from Williston after Owen. J., jugal; Pf., postfrontal; Po., postorbital; 
Qj., quadratojugal; Qu., quadrate; Sq., squamosal; St., supratemporal. 
jugal which joins in front both the jugal and the elongate postorbital. 
The supratemporal fossa lies between supratemporal, parietal, and 
postfrontal. 
Fig. I. — Skull of Ichthyosaurus longerons from the posterior aspect, after 
the restoration by Woodward. Occ. c., occipital condyle; Pa., parietal; 
Pt., pterygoid; Qj., quadratojugal; Qu., quadrate; S. occ., supra-occipital; 
Sq., squamosal; St., supratemporal. 
Tesiudinata .— Although no Testudinata are known earlier than 
the Jurassic, the order seems to be a very old one and to represent a 
side branch from the primitive reptilian stock, a view which receives 
