ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 293 
side by a sharp groove, which extends back to the orbit, on the lach- 
rymal bone. The profile of the skull is convex as far as the posterior 
boundary of the nostril, and very slightly concave from that point as 
far as the twelfth tooth. It then passes back as a straight, slightly 
ascending line, only interrupted by the lachrymal ridge, to the margin 
of the occiput. The inferior margin of the maxilla is convex down- 
wards as far as the canine groove, whose lower end is indicated by a 
deep sinuation. It then becomes convex again, the crown of the 
curve being at the ninth and tenth teeth, and its posterior end sweep- 
ing into a concavity whose summit is at the twelfth tooth. Behind this 
the edge of the maxilla is only slightly convex. The inferior contour 
of the jugal bone is very concave ; but the articular end of the quad- 
rate bone descends to the level of the edge of the ninth alveolus. 
The orbits have a sort of heart-shape, their apices being turned 
forwards, and their more convex sides inwards. 
The supra-temporal fosse are half-moon-shaped, their straight 
sides being external and so inclined that, if prolonged, they would 
decussate upon a line joining the anterior margins of the orbits. 
On the palatine surface of the skull, the premaxillo-maxillary 
suture runs backwards from the canine groove, as far as the level of 
the middle of the second alveolus behind the groove (or that of the 
seventh tooth), which point it reaches at about the junction of the 
middle with the inner third of the palatine plate of the maxilla. The 
suture then turns abruptly forwards until it reaches the level of the 
anterior margin of the alveolus of the sixth tooth, when it bends 
suddenly inwards to meet its fellow. The whole suture, therefore, 
has the form of a W. The vomers are completely hidden. 
The posterior nares look downwards and backwards ; their aper- 
ture is, from the incompleteness of the septum, single, and has a trans- 
versely elongated crescentic form. It measures 14 inch in width by 
&ths antero-posteriorly. The basi-sphenoid is seen for about {th of 
an inch on the base of the skull behind it, bounding the sides of the 
eustachian tube. The dental formula is — The fourth and tenth 
teeth are largest in the upper jaw, the first and fourth in the lower. 
The eight posterior teeth on each side in the upper jaw, and the five 
posterior in the lower, have a marked constriction between the short 
crown and the fang of the tooth. There are deep interdental pits for 
the reception of the mandibular teeth between the third and fourth, 
and fourth and fifth teeth above, and between the succeeding teeth 
from the sixth to the thirteenth. 
The hyoidean cornua are very strong curved bones, the chord of 
whose arc measures 34 inches. They are concave inwards, convex 
