MR. ST. GEORGE MIVART ON THE VERTEBRATE SKELETON. 381 
The learned Professor himself has modified the views he first put forward on the subject, 
as he himself states; for at first he was disposed to regard even the subcervical canal of 
the Pelican as the homologue of the thoracic hzemal arch*. 
This change of opinion is so far an approximation to the view which I venture to be- 
lieve is correct —namely, that neither the subcervical nor the subcaudal arches are homo- 
logous with hæmal ones, but are hypaxial and not paraxial parts. 
Professor Goodsirt differs from Professor Owen, and, while he deems it probable that 
the chevron bones are similar in nature to such parts as the subcervical canal of the 
Pelican, at the same time considers the hæmal arches (vertebral and sternal ribs) 
quite distinct from either. The true representatives in the tail of these hæmal arches 
of the trunk he takes to be the transverse processes with the aponeuroses extending down 
from them. In a note he says :—** In dissecting lately a large Crocodile, I found that 
an aponeurotic membrane extended outwards, and curved downwards on each side from 
the extremities of the caudal transverse processes. These aponeuroses met one another 
in the mesialline below the tail, and were there joined by a mesial aponeurosis which 
extended down from between the chevron bones. A layer of fat one-third of an inch 
in thickness lay on the outside of the lateral aponeuroses; and imbedded in it the 
hæmal divisions of the spinal nerves extended outwards, downwards, and backwards, like 
a series of intercostal nerves. The lateral muscular mass of the tail, arranged in myo- 
tomes with metamyotomie fibrous laminæ nearly as distinct as in the fish, lay on the 
outside of the layer of fat. Each of the lateral aponeurotie cavities was occupied by the 
*fémoro-péronéo-eoccygien' muscle of Cuvieri, which arose from the under surfaces 
of the transverse processes, the sides of the chevron bones, and mesial aponeurosis, and 
passed out of the cavity through a space left in its outer wall behind the ischium to be 
inserted into the thigh bone. The mesial membrane divided above, its two laminæ cor- 
responding to the limbs of the chevron bones, and passing in front into the walls of the 
pelvis.” He adds, “This arrangement appeared to me to indicate that the transverse pro- 
cesses and the lateral aponeuroses and the hæmal divisions of the spinal nerves, were in 
the position of the proper hæmal arches of the tail—that the two aponeurotie chambers 
constituted in fact, together, the abdominal or visceral cavity, divided by the mesial 
lamina, and occupied by a pair of muscles referable to that group of muscles which in 
the trunk lie on the inner surface of the visceral chamber—and that therefore the 
chevron-bones are not real hzemal arches, but subcentral developments." 
Dr. Cleland appears to take a similar view. He says$, “ In Saurians the inferior caudal 
arches are only in series with structures projecting into the interior of the visceral cavity à 
those in the anterior part of the tail so project; and further forwards, in series with 
maxillary, August Müller also demonstrates the small importance of the division or non-division of the costal ele- 
ment into. ‘rib, and ‘ transverse process.’ ” 
Professor Huxley in his Hunterian Lectures has brought forward numerous instances of diverse modes of ossi- 
fication of similar parts; and Professor Flower has done the same in his recent and first course of the same lectures. 
.* Geol. Trans, vol. v. 2nd Series, p. 519, pl. 44. figs. 2 & 3. + Loc. cit. p. 128. 
+ My femoro-caudal in Iguana, Menopoma, and Menobranchus, Proc. Zool, Soc. June 27, 1867, and April 22 and 
June 24, 1869. $ Loc. cit, p. 130. 
