Il4 REPTILES AND BIRDS, 
looks like a fold of the skin, pinched and drawn down, the two 
portions of it being in contact, like a dewlap.” It appears that the 
Cyclura also is exclusively herbivorous; and Mr. Gosse remarks 
upon the severe wounds it can inflict with its sharply-serrated tail. 
In general, the larger species of this family are solely vegetable- 
feeders, while the smaller kinds (such as the Anoles) are more or 
less insectivorous ; and there are some, of intermediate size, which 
even prey occasionally upon the kindred Anoles and other small 
animals. ‘The genera of these Reptiles are exceedingly numerous, 
as we have seen, and amongst so many there must be considerable 
variety in the habits; but we can only notice a very few of them. 
Within the limited area of the small archipelago of the Gallapagos, 
situated under the equator about ten degrees west of South America, 
there are two remarkable species of /gwanida, of which the habits 
have been described and commented upon by Mr. Darwin in his 
volume of the ‘Voyage of H.M.S. Beagle.” One of these is 
particularly so, because, as that naturalist observes, it is the only 
existing Saurian which can properly be said to be a marine animal. 
In the whole of that group of islands, as he tells us, there is only 
one rill of fresh water; yet this Reptile frequents the sea-beaches, 
and no other parts of the islands. He adds that it is the only 
known existing Lizard that feeds exclusively on aquatic productions. 
Although he refers both species to the genus Amblyrhynchus, the 
aquatic sort now constitutes the genus Oveocephalus of Dr. Gray, 
and it bears the name of O. créstatus. This lizard, according to 
Mr. Darwin, “is extremely common on all the islands throughout 
the archipelago of the Gallapagos. It lives exclusively on the rocky 
sea-beaches, and is never found—at least, I never saw one—even 
ten yards inshore. It is a hideous-looking creature, of a dirty black 
colour, stupid and sluggish in its movements. The usual length of 
a full-grown one is about a yard, but there are some even four 
feet long. I have seen a large one which weighed twenty pounds. 
On the Island of Albemarle they seem to grow to a greater size 
than on any other. ‘These Lizards were occasionally seen some 
hundred yards from the shore swimming about ; and Captain Colnett, 
in his ‘ Voyage,’ says, ‘they go out to sea in ‘shoals to fish.’ With 
respect to the object, I believe that he is mistaken; but the fact 
stated on so good an authority cannot be doubted. When in the 
water the animal swims with perfect ease and quickness, by a 
serpentine movement of its body and flattened tail—the legs, during 
this time, being motionless and closely collapsed on its sides. A 
seaman on board sank one, with a heavy weight attached to it, 
