LIVING IN THE SOCIETY’S MENAGERIE. 219 
has rarely been left without one or two individuals of this rare species. The typical 
specimen is stated to have been obtained at San Domingo; but of none of the speci- 
mens received by the Society is the exact origin known !. 
The description given by Duméril and Bibron applies to our specimens in every par- 
ticular, except in the following points. The teeth cannot be described as “ tricuspid ;” 
the central main cusp is free from denticulation, and two or three small notches indent 
the margin at some distance from the point of the tooth; towards the front the teeth 
are simply conical. ‘The teeth are larger than in Jguana tuberculata, twenty in each 
maxillary, six in the single intermaxillary, and twenty-two in each mandible. In the 
scutulation of the upperside of the head I observe that there are three pairs of scutes 
interposed between the nostril and frontal horn, the posterior and middle being conically 
raised. The nasal shield forms a direct suture with the rostral, without any intervening 
accessory scutes, as described by Duméril. 
The skeleton is very similar to that of Iguana (tuberculata). ‘The vertebre are more 
slender and depressed, and provided with much shorter and more feeble neural spines ; 
but their number is the same in both species, viz. six cervical, eighteen dorsal, and two 
sacral. Also the skull (Pl. XLIV.) is built entirely upon the plan of Iguana; but it is 
more massive and depressed, with a prolonged rostral region. The zygomatic arch is very 
broad; the parietals are horizontally spread out, not vertically as in Jguana, forming a 
broad roof over the occipital region. Again the fore part of the skull shows much firmer 
and more solid ossifications than in Iguana, the floor of the long oval nasal cavity being 
nearly entirely osseous. The posterior process of the articular of the mandible is 
short, and much more obtuse than in Iguana. 
The bones of the limbs do not show any noteworthy difference from those of Iguana; 
but they are throughout shorter. The following are the measurements taken from 
skeletons of Metopoceros and Iguana tuberculata which are of the same size, the 
vertebral column to the first caudal vertebra measuring 10 inches. 
Iguana. Metopoceros. 
millim, millim. 
IEReHICEUS ee sac a Se Se ciewss is ON gle Mienig mote 
iWilsavs Metin’ |e fateh, e.  eueiees ee 2h OE, Paar! aes 
Wirstyaietacarpal atny to) Mt a. att er Oe ete se 
hirspunrer inet: phalanx: 2-7) Seas Lite 2) oO eee 
Second metacarpal’ e-..t- seer) ava LGN oe ee omen 
Second finger, first phalanx . .. . . 10 8 
Second finger, second phalanx... . 11... .. 8 
sthirdemctacanpaliss eee sr cet 2! oa ALOR Seek m Ae ere bie 
Third finger, first phalanx. . . . . . 10 Fade ate: 
Third finger, second phalanx . . . . . 10 7 
Third finger, third phalanx ... . 12 7 
1 Tist of the Vertebrated Animals, 7th ed. p. 499. 
