304 
ORIGIN OF LIFE IN AMERICA 
belonging to the two genera Gonatodes and Phyllodactylus. 
The single species of Gonatodes is most closely allied to a 
species found in the West Indies, while the genus also occurs 
along the coast of Ecuador and Peru. Of the five species 
of Phyllodactylus, four are peculiar to the Galapagos archi¬ 
pelago and more or less nearly related to P. tuberculosus, the 
non-peculiar species being distributed along the west coast 
of Mexico, Central and South America as far as Ecuador. 
All the species of Tropidurus, a genus belonging to the family 
Iguanidae, are peculiar and closely related forms, most of 
them being confined to different islands. The genus is prin¬ 
cipally found in Peru and Ecuador. The two very large lizards 
which Darwin observed really belong to distinct genera. Two 
species of Conolophus are now recognised, while the aquatic 
form still retains the original name of Amblyrhynchus cris- 
tatus. Both genera of Iguanidae are quite peculiar to the 
archipelago and distantly related to a South American genus. 
Finally, the snake Dromicus biserialis, which is met with on 
seven of the islands, is nearly akin to D. chamissonis of Chile 
and Peru. 
The reptiles thus exhibit affinity with those inhabiting 
western South America, Central America and the West Indies. 
If they had reached the Galapagos islands by means of marine 
currents, as has been alleged, one may be tempted to ask the 
same question as I put before—Why should practically all the 
species belong to ancient types ? Giant tortoises seem to have 
become extinct on the continents in Miocene times, while the 
lizards of the archipelago belong to the two families Gecko- 
nidae and Iguanidae. Although no fossil representatives of the 
Geckonidae are known, the resemblance of their vertebrae to 
those of the Palaeozoic Microsauri has been commented upon 
as indicating their ancient lineage. The genus Phyllodactylus 
occurs in tropical xMnerica, in Africa, Madagascar, Australia 
and on Norfolk and Lord Howe’s islands in the Pacific. A 
single species inhabits the western Mediterranean region. The 
distribution of the genus, therefore, is suggestive of a very 
remote origin. Of the Iguanidae, as I have already pointed 
out, (p. 127), we know that they lived in America in Creta¬ 
ceous, and in Europe in Eocene times, while at present they 
are confined to North and South America with the outlying 
