SKELETON. 



649 



order must indicate the true character of those 

 osseous parts, whose various names serve to 

 blind us to the actuality of their homologous 

 caste. Examine closely the anatomical fact, 

 and see whether I am stretching the imagina- 

 tive faculty while I assert that the pubic (5,7) 

 and ischiadic bones (6, 8) of the bird {fig. 473. 

 ostrich) are actually springing from the lumbar 

 vertebrae like true ribs, (1. of the thorax). If, 

 therefore, it be the rule to affirm as incontest- 

 ible truth that these pubic and ischiadic bones 

 of the bird are counterparts of the bones so 

 named in the mammal, wherefore should we 

 stop here, and hesitate to name both orders of 

 bones (those of the mammal as well as of the 

 bird) as ribs originally ? 



Even up to the present hour we find the 

 osteologist strolling the Museum, and still 

 marvelling at the interrogative marsupial 

 bone (6, jig. 474.). What is it ? Whence is 



Fig. 474. 



(4), hold series with the marsupial bone (6), 

 just as this latter holds series with the ribs 

 (7, 8.) Does not this serial order prove the 

 identity of all these bodies in common ? Do 

 they not all alike abut against their sym- 

 metrical fellows at the common median line ? 

 Does not the pubic bone exactly correspond 

 with the sternal median line ? 



In fig. 475., representing the continuous 

 series of costiform bodies from the clavicles 



Fig. 475. 



Tlie thoracic and ventral median line of the Orni- 



thorhynchus, 



Showing the serial homology between the coracoid 

 bones (2), clavicles (1), ribs (3), and the marsu- 

 pial (6) and pubic bones (5). 



it ? What is its interpretation ? What else, 

 I answer, can it be, but a ventral rib, proper 

 to some one of the lumbar vertebrae behind. 

 If in these pages I have furnished the querist 

 with the idea that a lumbar vertebra has lost 

 costo-sternal quantity, then he cannot be un- 

 productive of the idea, that this marsupial 

 bone, which now occupies the place of this 

 costal quantity of the lumbar vertebra, is none 

 other than this quantity itself. Besides this, it 

 is also evident, from the serial order which the 

 marsupial bone (6, fig. 474.) holds with the line 

 of costs (3, 8, 7), that it is itself costiform. 



Now, in fig. 474., it will be also seen that 

 the pubic bone. (5), and the ischiadic bone 



The thoracic and ventral median line of the Crocodile 



(dorsal aspect'), 

 Showing the same serial order of the parts named 



in fig. 474. 



(1) to the ischiadic bones (4), it is scarcely 

 possible to recognise a difference between all 

 forms of this serial order. The clavicles (1) 

 are succeeded by the ribs (2, 3, 8), these by 

 the ventral ribs from (8 to 6), and these by 

 the pubic bone (5), and the ischiadic bone (4). 

 The homology between the bodies, (1) the 

 clavicle, and (2) the rib, is as clearly ap- 

 parent as between (5) the pubic bone, and (4) 

 the ischiadic bone. Moreover, the homo- 

 logy between (1 and 2), (5 and 4), is as 

 clearly apparent as between any two ribs of 

 the series. If (5) the pubic bone still held 

 its original place at (7), and had not discon- 

 nected itself from the ischiadic bone (4), it 



