288 ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 
parts, by the prolongation forwards of the nasal bones. The supra- 
temporal fossae are well-marked and open, though not large. The 
vomers do not appear in the palate. The feet are well webbed. The 
dorsal bony scutes are not articulated together; and there are no. 
ventral scutes. 
This genus contains only one species, the well-known Adigator 
Wisstssipiensis, or ducius, which is exclusively North American. 
Cuvier (Oss. Foss. ed. 4. vol. ix. p. 211) gives the appearance of 
the vomer in the palate as a general character of the A//gatores ; 
but this bone is not visible in the palate of any of those A//igatores 
which Cuvier would have referred to his A. /uczus or A. palpebrosus, and 
which form the genera l//zgator and Caiman as here defined. The 
vomers are in fact as slender and delicate as in the Crocodile, and 
extend only between the level of the tenth maxillary tooth an- 
teriorly and the descending processes of the prefrontal posteriorly. 
What may be called the median nares, or the arch formed by the 
postero-lateral part of the vomer and the anterior and superior lamina 
of the palatine bone on each side (which would constitute the posterior 
boundary of the posterior nares, if the palatine and pterygoid bones 
gave off no inferior or palatine processes), are situated nearly on a 
level with the twelfth tooth, or with the palato-maxillary suture. 
Genus 2. CAIMAN. 
Dental formula =” (Natterer). The face is without median 
or transverse ridges, but it is sharply angulated along a line which 
extends from the orbit forwards along the sides of the snout. The 
anterior nasal aperture is undivided in the dry skull. The vomers do. 
not appear in the palate. The supra-temporal fossz are obliterated, 
the circumjacent bones uniting over them. The webs of the feet are 
rudimentary. The dorsal scutes are articulated together by lateral 
sutures and anterior and posterior facets; and there is a ventral 
shield, consisting of similarly articulated scutes. 
Natterer! has described three species of Cazman—C. palpebrosus, 
C. trigonatus, and C. gibbiceps. The Caimans abound chiefly in 
tropical South America ; but they are found as far north as Mexico, 
a specimen of C. palpebrosus in Dr. Grant’s collection coming from 
that country. 
1 “ Beitrag zur naheren Kenntniss der Sudamerikanischen Alligatoren,” ‘Annalen des 
Wiener Mus.,’ Band i. 
