92 Walter Stapley : 



boundary between neck and thorax. In many birds and nianj rep- 

 tiles the coracoid bones migrate backwards and establish eight and 

 more neck bones, and as they go back they imperil rib-end after rib- 

 end, which becomes removed by the associated impulses. In This way 

 the long necks of birds and reptiles are apparently formed. 



Extinct Sea Lizards. — The Irhthyosaunts had cervical ribs. Thp 

 Plesiomurus had a long neck and no ribs on the first seven bone« : 

 it may be inferred that Phaiomiirits was slower in the water than the 

 Ichthyosaurus, and that it first developed its lung neck on swamijy 

 land, after which it became aquatic. 



Elevated Quadrupedal Reptiles. — The Brontosaurus had both a 

 long neck and tail, each of which contained nuuiy vertebrae. It had 

 attained a mode of progression that has some resemblance to mam- 

 uuilian C[uadrupedal progression. It would seem that these extinct 

 reptiles were not lifted from the ground l)y their limbs when seven 

 neck bones had been formed, and that body elevation in their case 

 only occurred after many neck bones had already been established. 



Fixed Mammalian Neck-type. — This is characterised by seven neck 

 bones devoid of cervical ribs, associated with a definite type of neck 

 curvature that is more or less marked. This type was established by 

 the mammalian body being lifted up from the ground by the limbs 

 when seven neck bones had been formed, an event that was accom- 

 panied by the suppression of the coracoid bones. 



Monotremes.- The monotremes show ne'ck structures transitory 

 between reptilian and mamnuilian type; the platypus, that lives 

 mostly in the water, has relatively larger coracoid bones than the 

 echidna, that lives on land and mostly in soil. It would seem that the 

 a.pproximation of the limbs to the ventral aspect to allow of burrowing 

 operations has been inimical to the coracoids. The echidna has 

 better fore-limb development and greater neck curvature than the 

 platypus. The straighter neck of the platypus contains cervical rib- 

 stumps, whereas the rib tissue in the curved neck of the echidna is 

 less of the nature of ri])-stumps and more of the nature of costal prn- 

 cesses. 



The echidna shows rib-stumps merging into costal processes ; 

 therefore the suppression of ribs into costal processes can be traced, 

 but I am unable to find evidence supporting the prevalent idea that 

 costal processes develoj) into cervical ribs, the term "costal proi.-ess "' 

 being taken as synonymous with vestigial ribs and not with the costal 

 rudiment. Iho echidna shows that under the impulses that raise the 

 body from the gi-ouiiil the curvature of \\\c neck lu'conies estahlislied, 

 and the rib-stunqis disappear into the costal processes. 



The hrst ribs of the monotremes dili'er from those of rei>tiles in 

 being attached to the sternum lyy hone ; tliey differ from mammals 



