96 MEMOIRS OF THE CARNEGIE MUSEUM 
grooye is supported by the quite heavy vertical plate of the splenial, but anteriorly 
the latter element is supplanted by the higher and thicker inner wall of the dentaries 
which here exceeds, the outer in height. In specimen No. 878 this inner wall, both at 
the anterior and posterior parts of the channel, shows some faint vertical ridges, indic- 
ative of alveolar compartments. Viewed from below the anterior portion of the den- 
taries is evenly rounded. Just below the outer alveolar border is a shallow channel 
into Which several vascular foramina open at the anterior end of the jaw. 
Splenial (spl.).—The splenial in Baptanodon as in the other members of this fam- 
ily is a long vertical plate that is applied to and forms the greater portion of the inner 
surface of the posterior part of the ramus. The anterior portion extends below the 
dentary a little and is visible from a lateral view of the mandible. Anteriorly it 
meets its fellow medially where they unite and pass between and under the dentaries. 
These appear to be ankylosed at the symphysis. (See fig. 2.) Posteriorly the lower 
margin of the splenial is gradually confined to the inner side and rises obliquely for 
a considerable distance. This suture at the posterior end of the jaw is obscure and 
the boundary between the splenial and coranoid (?) cannot be determined, but the 
latter element probably continues to the end of the ramus, lapping along the inner 
side of the articular, assisting the angular and surangular in holding that element 
in position. (See Pl. XL., fig. 2.) On the internal surface, just posterior to the symphy- 
sis is an elongated oval foramen that probably represents the ‘‘internal mandibular 
foramen” of the crocodile, though in this case it appears to be wholly enclosed by 
the splenial while in the crocodile the splenial only forms the anterior border, 
Posterior to this foramen, froma point on the lower inner side of the mandible, radi-, 
ating linear impressions extend forward and upward to the posterior border of the 
vacuity. They would seem to indicate a surface for muscular insertion. 
Surangular (s.ag.).— Viewed laterally the surangular is a long slightly-bent bone 
that forms the upper posterior margin of the ramus. On its inner posterior side this 
bone develops a concave surface (see sq., fig. 3) which with the anterior end of the 
articular forms the articulating surface for the quadrate. Just in front of this artic- 
ulating surface is a node-like protuberance which Frass has pointed out as an 
arrangement to prevent the dislocation of the lower jaws. (See fig. 3.) 
The posterior part of the suture between the angular and surangular is not shown 
by this miterial, though it is indicated by a dottel line, after the fractures on the 
rami of No. 878 which were considered as taking the course of these breaks. Ante- 
riorly the surangular gradually tapers to a point which from a lateral view disap- 
pears between the dentary and angular just below the nares, although the elements 
are continued still farther forward on the inside. (See s.ag., fig. 1.) ‘The lateral sur- 
