388 MR. ST. GEORGE MIVART ON THE VERTEBRATE SKELETON. 
With regard to the descending arches, it may be that more than one pair belongs to 
each vertebral element, just as in some fishes there are two neurapophyses on each side 
to a single centrum. But as they are hypaxial and not paraxial in nature, there is no 
embarrassment in assigning some of them, in fishes, to vertebræ provided with true 
costal elements. 
Such are the results which seem to me to follow from the study of the vertebrate 
axial skeleton, in the light afforded by the works and labours of the authors before 
referred to; and if these results are not themselves correct, 1 trust they may neverthe- 
less contribute (as I before said), by provoking further examination and criticism, to 
the elucidation of truth on this somewhat puzzling question. 
THE APPENDICULAR SKELETON. 
That this part of the skeleton is an independent, separate part, and no mere modifi- 
cation of any of the before described axial elements, has, I think, been satisfactorily 
demonstrated by previous writers. 
The serial homology between the parts of the anterior and posterior limbs of the same 
side* has also been pretty satisfactorily determined. The femur answers to the humerus, 
the tibia to the radius, the hallux to the pollex, &c. (Plate LIII. fig. 1). 
But can the limb-skeleton have a yet simpler expression than a mere statement of 
their average development in the higher classes ? can we reduce it to a form in which it 
shall eorrespond to piscine structures also, and reveal genetic relationships ? 
Professor Gegenbaur, i in a recent paper}, has given an affirmative answer to this ques- 
tion. 
From a consideration of the limb-bones of Ichthyosaurus, Plesiosaurus, Amphibia and 
Elasmobranchs, he comes to the conclusion that a common form may be arrived at, a 
type at once of both fin and limb, according to the figure which I have had copied (fig. 4). 
He conceives that the increasing number of parts as we proceed distad from the root 
of the limb, is owing to the limb having originally consisted of a fin with a marginal 
chain of ossicles (H, R, 7, c', m, &c.) and with a secondary longitudinal series of ossicles 
attached to the distal end of each marginal ossicle, all the series ending at about the 
same level transversely. "Thus the root marginal ossicle, H, (the future humerus or 
femur) would have attached to one side of its distal end a chain of ossicles (U, w, €, m’, 
&e.), the future ulna, cuneiforme, part of unciforme, fifth metacarpal, and phalanges of 
fifth digit. "The second marginal ossicle (the future radius) would have attached to one 
side of its distal end a chain of ossicles (3, c, e*, m', &c.), the future lunare, first part 
of os centrale, other part of unciforme, fourth metacarpal, and phalanges of fourth digit. 
The third marginal ossicle, r (the future scaphoid), would have attached to one side 
of its distal end a chain of ossicles (c, e”, m’, &c.), the future second part of os centrale, 
* That special relationship between the ilium and scapula, with the attached muscles, which I had the honour of 
suggesting in a paper published in the Linnean Society's Transactions (vol. xxv. p. 395) has been accepted, con- 
firmed, and reinforced by Professor Flower in his recent course of Hunterian Lectures. 
+ Ueber das Gliedmaassenskelet der Enaliosaurier. Von C. Gegenbaur, Jenaischen Zeitschrift, Bd. v. Heft. 3. 
