HERPETOLOGY OF PORTO RICO. 671 



Haiti, one from the latter agrees at least partly with the former in 

 the relation of the rostral to the nasals. 



In our four Mona Island specimens (the Hamburg specimens were 

 not examined for this character) the frontal median horn is separated 

 from the nearest prefrontal shield or horn by a double row of scales. 

 In the type of C. cornu^a there seems to be no intervening series at 

 all ("la troisieme plaque * * * touche a la protuberance frontale," 

 Dumeril and Bibron, p. 212); in the Cambridge specimen '"the horn is 

 separated from the hindmost of the three enlarged scales by a single 

 row of very narrow scales" (S. Garman in letter); according to Dr. 

 Siebenrock's statement to me the Vienna specimen from Gonaives has 

 likewise only one row of intervening scales, and as he makes no excep- 

 tion for the second specimen I conclude that this is similar. 



As will be noted further on, there may be other differences, more 

 important, perhaps, though less obvious, but which have not been 

 verified in the whole series. There is consequent!}- very good reason 

 for believing that the Mona Island iguana is distinct, and I would 

 have hesitated but little to describe it as such were it not for Dr. Giin- 

 ther's description and figure of a specimen from an unknown locality 

 in the Zoological Garden of London." These agree so minutely with 

 the specimens from Mona that if his specimen did not come from 

 that island the idea of the existence of two species would most likely 

 have to be abandoned, for it must be admitted that the chances of a 

 Mona Island iguana having found its way to the Zoological Garden in 

 London as early as 1882 are very slight, and it is certainly much more 

 likely that it came from Haiti or Santo Domingo. There is of course 

 a possibility that two forms occur in the latter island, one of which is 

 identical with the Mona form, but the whole matter is thrown into 

 such uncertainty that it seems best to await the accumulation of more 

 authentic material before deciding. 



In calling attention to the differences thus far noticed others may lie 

 in a position to judge better, and I therefore subjoin the few additional 

 notes which I made in comparing the three specimens from Haiti and 

 Mona in the museum at Hamburg. In the adult Mona specimen I 

 found the enlarged keeled scales on the forearm much smaller than in 

 the one from Haiti (ratio 20 to 12), the preauricular tubercles were 

 much larger, also the median frontal horn; the two combs on the third 

 toe were very large in the one from Mona, much larger than in the 

 Haitian specimen. 



Description. -Youmj; U.S.N.M. No. 29367; Mona Island; August, 

 1901; B. S. Bowdish, collector. Rostral wide, as wide as mental, 

 broadly in contact with nasals; nasal large, ovoid, perforated by a large 

 nostril of the same shape; on each side of the top of the snout, immedi- 

 ately behind and adjoining the nasal, a series of three large shields, 



« Trans. Zool. Soc, XI, 1882, p. 218, pi. xliv. 



