290 ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 
the nasal plate of the palatine bone. In front of its junction with the 
maxilla, the horizontal plate of the vomer presents a long free edge, 
concave externally ; and this bounds the median nares internally and 
posteriorly. Throughout its junction with the maxilla, the horizontal 
plate is parallel-sided ; but after it joins the palatine bone, it gradually 
narrows posteriorly, in consequence of the gradual increase in width 
of the palatine, and ends almost in a point, 64 inches behind its 
anterior end. The posterior edge of the vertical plate is extremely 
thin, and {ths of an inch deep. It articulates with the anterior end of 
the vertical plate of the pterygoid, while the straight inferior edge 
articulates throughout with the palatine plate of the palatine bone. 
The vomers terminate midway between the median nares and the 
descending process of the prefrontal. The median nares are bounded 
entirely by the vomer and the maxilla. They correspond with the 
nasal face of the palato-manillary suture, but are rather behind its 
palatine face, and they are about on a level with the interval between 
the tenth and eleventh teeth. If the anterior edge of the palatine 
bone bounded them, they would be a little behind the twelfth tooth. 
The posterior nares, 24 inches wide, by §ths of an inch long, look alto- 
gether downwards, are completely divided by a bony septum, and 
have the form of a rhomboid with its narrowest side posterior. They 
are surrounded by a strong raised ridge, incomplete only at the 
anterior and outer angles of the rhomboid. 
Five species of /acare are enumerated by Natterer—/. fisszpes, 
J. sclerops, J. nigra, J. punctulata, and J. vallifrons. They have been 
met with only in South America. 
IT. In the family of the CROCODILID& the teeth are usually strong 
and very unequal in size, and there is always a considerable difference 
between the anterior and the posterior teeth. The two anterior man- 
dibular teeth are received into pits in the premanilla ; but the canines 
pass into grooves (which may be converted into fossa) situated at the 
junction of the premanilla and maxilla. The other mandibular teeth 
are received between the manillary teeth. The symphysis of the 
lower jaw does not extend beyond the level of the seventh or the 
eighth mandibular tooth. The premaxillo-maxillary suture may be 
either straight or strongly convex backwards. The divided vomers 
do not appear in the palate. The posterior nares look more or less 
backwards, and are transversely elongated. The supra-temporal 
fosse are always open, and the feet are distinctly webbed. The 
dorsal scutes are not articulated ; and there are no ventral scutes. 
Two genera, Crocodtlus and Mectstops, are distinguishable in this 
family. 
