224 The American Naturalist. (March, 
The genus Tropidurus of the Iguanidz shows better than any 
other form the peculiar specialization on the different islands. I 
have already in a former paper spoken about the variation of this. 
lizard. I reached the following result : 
1. Each island has only a single variety or species of Tropidurus. 
2. Nearly every island has a peculiar variety or species of Ti ropidurus. 
These results were based on 128 specimens of Tropidurus collect- 
ed by the “ Albatross” on eight islands, namely : Chatham, Hood, 
Gardner (a little islet northeast of Hood), North Albemarle 
(Tagus Cove), James, Duncan, Indefatigable, Abingdon. 
The first species of Tropidurus described from the Galapagos 
was T. grayii Bell, the type specimens of*which had been collect- 
ed by Darwin on Charles and Chatham Islands. I have taken the 
form from Charles Island, of which the “ Albatross” did not get 
any specimens as the type of Tropidurus grayii, because Chatham 
Island is inhabited by a distinct form, which has been described as 
T. lemniscatus by Prof. Cope. Specimens from Indefatigable and 
James Islands are very much alike, and probably different from the 
specimens from Charles Island. I named these T. indefatigabilis. 
The peculiar form from Duncan Island was called 7. duncanensis ; 
that from Hood and Gardner Islands T. delanonis ; the Albemarle 
form T. albemarlensis ; that from Abingdon T. abingdonii; the 
Bindloe forms were considered as typical for T. pacificus Steind. 
No conclusion could be reached in regard to T. bivittatus Peters 
and T. pacificus (var. habeli) Steind., the localities of these 
forms not being known. ` 
The following table shows the number of scales round the mid- 
dle of the body in the different forms: „Tropidurus indefatigabilis 
Baur, 55-59; Tropidurus lemniscatus Cope, 55-61 ; Tropidurus 
albemarlensis Baur, 57—63 ; Tropidurus grayii Bell, 55-65; T yopi- 
durus duncanensis Baur, 72-79; Tropidurus delanonis Baur, 
-82-85 ; Tropidurus pacificus Steind., 85-90 ; Tropidurus abingdonit 
Baur, 95-101. 
The specimens from Jervis figured by Steindachner as T. grayi 
are probably identical or closely related to 7. indefatigabilis. No- 
thing is known of these lizards from Brattle, Barrington, Tower, 
Wenman, Culpepper, Narborough. . I do not doubt that on most 
