262 REPORT— 1846. 
side of the centrum or the base of the neural arch, called ‘diapophysis,’a di- 
stinet part from the autogenous parapophyses in fishes. The anterior verte- 
bre of crocodiles have an exogenous inferior transverse process from the side 
of the centrum, answering to the ‘parapophysis,’ as well as an upper transverse 
process or ‘ diapophysis ’ developed from the base of the neurapophysis : and 
the proximal end of the pleurapophysis bifurcates and articulates with both 
transverse processes, circumscribing with them a foramen at the side of the 
‘centrum. The same structure obtains in the cervical and anterior thoracic 
vertebra of birds and mammals: thus the rib (p/) in fig. 15 articulates to the 
parapophysis p and the diapophysis d. Very few, however, of the thoracic 
ribs in the cetaceans offer this structure; the first or second may reach the 
centrum, but the rest are appended to the ends of the long diapophyses, and 
a character of affinity to the saurians is thus manifested. The cervical re- 
gion is distinguished by the brevity of the pleurapophyses and the absence 
of bony hemapophyses, in saurians, birds, and mammals ; but in the warm- 
blooded classes the short floating vertebral ribs soon anchylose to the diapo- 
physes and parapophyses, and constitute thereby the ‘anterior roots of the 
perforated transverse process’ of anthropotomy*. ‘The cervical pleurapo- 
physes are indicated diagrammatically at p/, in the neck of the embryo skele- 
ton (fig. 25): those of the seventh cervical vertebree sometimes attain in 
the human subject proportions which acquire for them the name of ‘ribs.’ 
The pleurapophyses retain their moveable articulation in the ninth, and 
sometimes the eighth, vertebrae of the elongated neck of the three-toed 
sloths f. 
. The thoracic or dorsal vertebrze of mammalia are characterized by the free ar- 
ticulations of the pleurapophyses (fig. 25, pl) : most of these are much-elon- 
gated, and most, if not all, support hemapophyses (ib. /) ; which, in a greater 
or less number of the anterior vertebree, articulate with beemal spines (ib. As), 
completing the arch: these spines commonly remain distinct, and are called, 
some ‘sternebers,’ others ‘manubrium,’ and ‘ xiphoid appendage,’ and to- 
gether they constitute the ‘sternum.’ In most mammals the thoracic hema- 
pophyses are cartilaginous: they become ossified in Dasypus, Myrmecophaga, 
the megatherioids and monotremes. The hinder pleurapophyses, which pro- 
gressively diminish in length, also, usually become simply suspended to the 
diapophyses: all the ribs are so attached in Balena longimana, according 
to Rudolphi. The lumbar vertebra, which in some mammals show, in the 
foetal state, distinct rudiments of pleurapophyses more minute than those 
in the neck, have them soon anchylosed to the extremities of the diapo- 
physes, which are thus elongated; and the vertebra is characterized in anthro- 
potomy as ‘ having no ribs, but simple imperforate transverse processes.’ The 
hzemapophyses of these segments of the skeleton are represented by the 
‘inseriptiones tendinex’ (fig. 25, h'') ; they do not advance even to the state 
of cartilage, but retain the primitive condition which they presented in the 
corresponding part of the trunk in fishes. 
If a vertebra succeeding the lumbar or abdominal ones have its hemal 
arch completed, as in the thorax, by pleurapophyses and hzmapophyses, 
with diverging appendages, forming the ‘pelvic arch and hind or lower 
limbs,’ it is called a ‘sacrum’ (fig. 28, p', H, A). If two or more vertebre 
anchylose together, without such completion of the typical character, they 
likewise are said to form a ‘sacrum,’ of which an example may be found in 
* Meckel, Archiv fiir Physiologie, B. i. (1815) p. 594, pl. vi. fig. 12, e; and System der Ver- 
gleichend. Anatomie, B. ii. p. 294. . 
t+ Prof. Th. Bell, Trans. Zool. Society, i. p. 115. pl. 116, a, . 
