140 
SYSTEM OF NATURE. 
pearance, closely resembling the impression of hair, observable on the 
stone in which the bones of these animals are found : indeed it was thus 
considered by the earlier writers on the subject, and from this circum¬ 
stance, in combination with others, the remains were supposed to be 
those of mammals. The saurian hypothesis must, however, seek another 
explanation of the phenomenon, since a covering of hair is unknown 
amongst lizards. Agassiz, as quoted by Professor Buckland, therefore 
suggests that the striated surface of the stone was due to the impression 
of the minute foldings of the contracted membrane of the wings, but 
no sooner have our philosophers arrived at this conclusion, than a second 
difficulty appears to arise out of the first; how does it happen that the 
impression of so delicate and perishable a membrane as that of which 
the wings are composed should be thus beautifully preserved, while all 
trace of scales — those distinguishing features of lizards, and which in 
fishes defy the efforts of time — is utterly obliterated ? Professor Buck- 
land cuts the Gordian knot. “ It is probable,” says that eminent geolo¬ 
gist, “ that the pterodactyles had a naked skin, * * * because the 
weight of scales would have encumbered their movements in the air.” * 
I am not aware whether this passage will strike my readers as it strikes 
myself, but the reasoning does not appear to me quite conclusive which 
uses the entire absence of scales as an argument in support of the hypo¬ 
thesis that the pterodactyles were lizards. 
In conclusion, I must beg to repeat that these observations simply 
refer to the apparent incompleteness of the saurian hypothesis : I reserve 
for the pages of ‘ The Zoologist ’ my arguments in favour of another 
theory. 
No. 7. 
Page 54, line 13.—“ Uniformity and equal value .” 
I have long cherished, and frequently expressed an opinion, that all 
groups bearing similar titles should be precisely equivalent. At present 
* Br. Tr. ii. 32 , note. 
