CHARACTERS OF RECENT CROCODILTA. 5 



the anterior extremity, tlie vomer is a thin vertical plate of bone, 

 ■|ths of an inch deep, which articulates below with the 2)alatiiie 

 plate of the maxilla, and, about 1 inch behind this, with the pala- 

 tine plate of the palatine bone. The upper edge of this plate nowhere 

 extends to one-third of the height of tlie nasal chamber. It gives 

 off a horizontal process outwards, which, gradually increasing 

 in width, inclines downwards until it comes into contact, first, 

 with the inner surface of the maxilla, and, fths of an inch behind 

 this, with 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 bovmds the median 

 nares internally 9,nd posteriorly. Throughout its junction with tlie 

 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, 6| 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 ptery- 

 goid, while the straight inferior edge articulates throughout Avith 

 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-maxillary 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 woiild be a little behind the twelfth 

 tooth. The posterior nares, 2-1- inches wide, by |-ths of an inch 

 long, look altogether 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, incom- 

 plete only at the anterior and outer angles of the rhomboid. 



Five species oi Jacare are enumerated by Natterer— Jlj^s^^^je^, 

 J. selerops, J. nigra, J. punctulata, and J. vallifrons. They have 

 met with only in Soiith America. 



II. 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 mandibular teeth are received into pits in the premax- 

 illa ; bvit the canines pass into grooves (which may be converted 

 into fossae) situated at the junction of the premaxilla and maxilla. 



