ON THE VERTEBRATE SKELETON. 327 
osseous rudiments of pleurapophyses ; and the neural spine is commonly un- 
developed. One or more typical segments are obviously completed by the 
meeting of the broad sides of the inverted arch (62, #3, 61) at the ‘ ischio- 
pubic symphysis’ forming the ‘pelvis’ of anthropotomy. Before, however, 
entering upon the difficult inquiry into the general homology of the pelvis, 
I would beg to refer the reader to the analysis of the sacrum of the ostrich 
given at p. 263: and I here subjoin a figure of seven of those vertebre, 
from an immature specimen, the pleurapophyses being removed from all 
_ save the last (pi), in order to show the change of place of the neurapophyses 
m1—4,in relation to their centrums, c 1 to 4: dd are the long diapophyses ; 
the short parapophyses. The sacral spines, s s, are enormously developed. 
In the bird the modification of the vertebral segments at the posterior 
region of the trunk in relation Fie. 27 
to the transference of the whole Reels 
weight of the body and fore- 
limbs (wings) upon the hind- 
limbs, is greater and more ex- 
tensive than in the ‘bipes im- 
plume,’ and the essential nature 
of the pelvic arch is still more 
masked in the bird than in man. 
In order to obtain an insight 
into the model according to 
which it is constructed, we must 
descend still lower, even to the 
humblest of the vertebrated 
creatures that crawl upon the 7 sacral vertebree of a young ostrich (Struthio camelus), 
_ earth. The example which is here selected for that purpose is the perenni- 
branchiate amphibian calleq Menopome Alleghanniensis. 
The three anterior ver- Fig. 28. 
tebrz which answer in po- 
sition to the ‘lumbar’ in 
_ fig. 25, differ chiefly in ha- 
_ ving rudimental pleurapo- 
physes (P/) articulated to 
_ the ends of the diapophyses 
(D). In the next vertebra 
thediapophysis(D')andthe 
_ rudimental pleurapophysis 
(Pl) are thickened and 
_ enlarged: a second pleur- 
_ apophysial rib-like piece(62) 
__ is joined by one end to the 
4 pleurapophysis, and by the Sacral vertebra and appendage with contiguous vertebrze. Menopome. 
other to a broad partially ossified cartilage (61) which meets and joins its 
fellow, completing a hemal arch and restoring the vertebra in question to 
the typical character. A radiated appendage, moreover, diverges on each 
side from the articulation between 62 and 641, and forms the hind-limb. Now 
the special homology of this limb with the undivided filamentary appendage 
similarly situated in the lepidosiren, and with the ventral fins of fishes, ‘jn 
the descending series ; and with the hind-limb of other reptiles, of birds and 
of mammals in the ascending series, is unmistakeable, and, I believe, is gene- 
_ rally admitted: so that comparative anatomists have not hesitated to call 
_ the rib-like bone, 62, ‘ilium,’ and the part, 61, ‘ pubis” in the menopome. 
= 
