58 DICTIONARY OF BIRDS 
the present to regard asa Subclass, separated into three Orders—Odontolce, 
Odontotormx and Sawrure—all well marked, but evidently not of equal 
rank, the last being clearly much more widely distinguished from the 
first two than they are from one another. But that these three oldest- 
known forms of Birds should differ sc greatly from each other unmistak- 
ably points to a great antiquity for the Class. All are true Birds; but 
the Reptilian characters they possess converge towards a more generalized 
type. He then proceeds to treat of the characters which may be expected 
to have occurred in their common ancestor, whose remains may yet be 
hoped for from the Paleozoic rocks, or at least from the Permian beds that 
in North America are so rich in the fossils of a terrestrial fauna. Birds, he 
believes, branched. off by a single stem, which gradually lost its Reptilian 
as it assumed the Ornithic type ; and in the existing Ratitz we have the 
survivors of this direct line. The lineal descendants of this primal stock 
doubtless at an early time attained feathers and warm blood, but, in his 
opinion, never acquired the power of flight, which probably originated 
among the small arboreal forms of Reptilian Birds. In them even rudi- 
mentary feathers on the fore-limbs would be an advantage, as they would 
tend to lengthen a leap from branch to branch, or break the force of a 
fall in leaping to the ground. As the feathers increased, the body would 
become warmer and the blood more active. With still more feathers 
would come increased power of flight as we see in the young Birds of 
to-day. A greater activity would result in a more perfect circulation. <A 
true Bird would doubtless require warm blood, but would not necessarily 
be hot-blooded, like the Birds now living. Whether Archxopteryx was on 
the Carinate line cannot as yet be determined, and this is also to be said 
of Ichthyornis ; but the biconcave vertebrae of the latter suggest its being 
an early offshoot, while it is probable that Hesperornis came off from the 
main ‘Struthious” stem and has left no descendants. 
From this bright vision of the poetic past—a glimpse, some may call 
it, into the land of dreams—we must relapse into a sober contemplation 
of the prosaic present—a subject quite as difficult to understand. The 
former efforts at classification made by Sundevall have already several 
times been mentioned, and a return to their consideration was promised. 
In 1872 and 1873 he brought out at Stockholm a Methodi Naturalis 
Avium Disponendarum Tentamen, two portions of which (those relating to 
the Diurnal Birds-of-Prey and the ‘ Cichlomorphe,” or forms related to 
the Thrushes) he found himself under the necessity of revising and modi- 
fying in the course of 1874, in as many communications to the Swedish 
Academy of Sciences (K. V.-Ak. Férhandl, 1874, No. 2, pp. 21-80; No. 
3, pp. 27-30). This Tentamen, containing a complete method of classify- 
ing Birds in general, naturally received much attention, the more so 
perhaps, since, with its appendices, it was nearly the last labour of its 
respected author, whose industrious life came to an end in the course of 
the following year. From what has before been said of his works it may 
have been gathered that, while professedly basing his systematic arrange- 
ment of the groups of Birds on their external features, he had hitherto 
striven to make his schemes harmonize if possible with the dictates of 
internal structure as evinced by the science of anatomy, though he 
