ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 289 
Genus 3. JACARE. 
The snout is broad, and rounded at the end. Each prefrontal 
bone is traversed close to its anterior extremity by the ends of a 
strong transverse ridge, which then curve round and pass forwards on 
the lachrymal and maxillary bones, to subside opposite the ninth 
tooth. The anterior nasal aperture is not divided by bone. The 
vomers, separated by a longitudinal suture, appear in the palate 
between the premanillaries andthe palatine plates of the maxillaries. 
The temporal fossa, though not large, are open. The webs of the 
feet are small. The dorsal scutes are articulated together, as in the 
preceding genus; and there are similarly-articulated ventral scutes. 
There are 18—20 teeth on each side, above and below; and the fourth 
tooth in the upper jaw is the largest. The mandibular symphysis 
extends back nearly to the fifth tooth. 
In a skull of /acare (fisstpes ?), 19 inches long, in the British 
Museum, I find that part of the vomer which is visible in the palate 
to be a rhomboidal plate, somewhat truncated anteriorly, and rather 
more than 14 inch long and 1 inch wide. Its anterior end comes 
within $ths of an inch of the posterior margin of the anterior palatal 
foramen. Its posterior margin reaches to the leves of the eighth 
tooth. The visible portion of each vomer is only its anterior end, 
which forms a thick and solid wedge-shaped plate, broader in front 
than behind, and articulating by a rough anterior and outer face with 
the premaxilla by an obliquely ridged posterior and outer face with 
the maxilla, and by its internal face with its fellow. Its upper, 
rounded surface projects but little into the nasal passage. 2} inches 
behind its anterior end, the posterior and upper extremity of the 
vomer passes into a thin and narrow plate of bone, whose plane 
is at first inclined at an angle of 45° to that of the anterior part 
of the bone, but gradually becomes vertical ; as it does so it deepens 
until, 3 inches behind the anterior extremity, the vomer is a thin 
vertical plate of bone, 8ths of an inch deep, which articulates below 
with the palatine plate of the manilla, and, about 1 inch behind this, 
with the palatine plate of the palatine bone. The upper edge of this 
plate nowhere extends to one-third of the height of the nasal chamber. 
It gives offa horizontal process outwards, which, gradually increasing 
in width, inclines downwards until it comes into contact, first, with 
the inner surface of the maxilla, and, #ths of an inch behind this, with 
1 According to Natterer, the dental formula of J. nigra and /. fissipes is — of /. 
O—20 
19—19 5 ihe . al 
sclerops ~~ of J. valléfrons and J. punctualata = 
VOL. II. U 
