170 PROFESSOR OWEN ON THE DEVELOPMENT AND HOMOLOGIES OF THE 
to seek for examples in which ordinary elements of the endo-skeleton are extended 
between the pelvis and the ventral integuments. Not to speak of the Plesiosaurus 
(fig. 7)5 in which the underlapping of the pubic-bones 64, by the abdominal ribs Qi), 
might be due to displacement of the fossilized parts ; the Puffins {Fratercula), the 
Guillemots {Uria) (fig. 9), and other common sea-birds of our coasts give the examples 
of the sternum prolonged backwards to beyond the vertical line traversing the aceta- 
bulum ; whilst the hsernapophyses (Ji, Ji, ossified cartilages) of the three or four pos- 
terior ribs extend backwards beyond or as far as the most backwardly prolonged 
parts of the pelvis (ea, 64), exactly in the relative 
position which the xiphisternals and hyposter- 
nals bear to the pelvis of the Chelonia. 
In this comparison it is interesting also to 
discern the harmony which pervades the same 
vertebral elements in the characteristic forms 
which they assume in the same species. In the 
sea-birds cited the ossa pubis (64), or the hsem- 
apophyses of the pelvic arch, are long and slen- 
der, like the costal hsernapophyses {h) beneath 
them : in the Chelonian reptiles the ossa pubis 
(64) are broad and expanded, like the costal hse- 
mapophyses {ps, xs), which equally intervene 
between them and the ventral integument. 
Nature is ever liberal in rewarding with the 
perception of such harmonies whoever patiently 
investigates and rightly comprehends her ar- 
. Belations of thoracic to pelvic hsernapophyses, Plesiosaurus. 
rangements. 
Fig. 8. 
Relations of thoracic to pelvic hsernapophyses, Chelonian. 
Fig. 9. 
Relations of thoracic to pelvic hsernapophyses. Bird {Uria Troile). 
