398 
MESSRS. E. M. BALEOUR AND W. N. PARKER ON THE 
Comparison of the vertebral column of Lepidosteus with that of other forms . 
The peculiar form of tlie articulatory faces of the vertebrae of Lepidosteus caused 
L. Agassiz (No. 2) to compare them with the vertebrae of Beptiles, and subsequent 
anatomists have suggested that they more nearly resemble the vertebrae of some 
Urodelous Amphibia than those of any other form. 
If, however, Gotte’s account of the formation of the amphibian vertebrae is correct, 
there are serious objections to a comparison between the vertebrae of Lepidosteus and 
Amphibia on developmental grounds. The essential point of similarity supposed to 
exist between them consists in the fact that in both there is a great development of 
intervertebral cartilage which constricts the notochord intervertebral]v, and forms the 
articular faces of contiguous vertebrae. 
In Lepidosteus this cartilage is, as we have seen, derived from the bases of the 
arches ; but in Amphibia it is held by Gotte to be formed by a special thickening of 
a cellular sheath round the notochord which is probably homologous with the carti¬ 
laginous sheath of the notochord of Elasmobranchii, and therefore with part of the 
notochordal sheath placed within the membrana elastica externa. 
If the above statements with reference to the origin of the intervertebral cartilage 
in the two types are true, it is clear that no homology can exist between structures so 
differently developed. Provisionally, therefore, we must look, elsewhere than in 
Lepidosteus for the origin of the amphibian type of vertebrae. 
The researches which we have recorded demonstrate, however, in a very conclusive 
manner that the vertebrae of Lepidosteus have very close affinities with those of 
Teleostei. 
In support of this statement we may point: (l) To the structure of the sheath of 
the notochord; (2) to the formation of the greater part of the bodies of the vertebrae 
from ossification in membrane around the notochord; (3) to the early biconcave form 
of the vertebrae, only masked at a later period by the development of intervertebral 
cartilages; (4) to the character of the neural arches. 
This latter feature will be made very clear if the reader will compare our figures of 
the sections of later vertebrae (Plate 29, fig. 78) with Gotte’s* figure of the section 
of the vertebra of a Pike (plate 7, fig. 1). In Gotte’s figure there are shown similar 
intercalated pieces of cartilage to those which we have found, and similar cartilaginous 
dorsal processes of the vertebrae. Thus we are justified in holding that whether or 
no the opisthocoelous form of the vqrtebrae of Lepidosteus is a commencement of a 
type of vertebrae inherited by the higher forms, yet in any case the vertebrae are 
essentially built on the type which has become inherited by the Teleostei from the 
bony Ganoids. 
* “Beitrage zur vergl. Morpkoh cl, Skeletsystems d. Wirbeltlieire.” Arcliiv. f. Mikr. Anat., vol. xvi., 
1879, 
