90 W(dier Shipley: 



animal. As the j^irdle passed down the neck, the cervical vertebrae 

 were denuded of their ribs, to a greater or less extent, according to the 

 activity of the neck movements. 



The fore-limbs of ('erotodus, the lung-fish of Queensland, thou.gh 

 only slightly developed, are somewhat larger than the fore-'imbs of 

 pectoral tins of ordinary fish. It seems most probable that the slight 

 increase in size of these puny fore-limbs is the result of impulses that 

 have resulted from contact with mud. Ribs are present in the neck 

 area and throughout the remainder of the body cavity. 



The Menopome, which Owen descriljes on page 4S, vol. I. of the 

 1866 edition of Comparative Anatomy, shows some Hiuli and neck 

 development. Small ri])s oi-cur throuuhniit the l)ody and necl\ of 

 this amphibian. 



Tracliysaiirus riK/osi/s, compared with Cf^ratod i"<, shows a great 

 development of the pectoral girdle, a development which expresses th-j 

 construction of a bony carriage that is used to convey not only the 

 fore-limbs down the neck as they progressively develoj), but also the 

 heart from a position of threatened danger to one of secured safet}% 

 that is from the throat to the chest. In this lizard the pectoral 

 girdle embraces the heart in what corresponds to the gill-area, beneath 

 the neck, and spreads itself over and above the cervical ribs. As the 

 j^ectoral girdle bears the heart and fore-limbs down the neck, the 

 cervical ribs are reduced to rilj-stumps, a condition that is remaik- 

 ably well shown in the crocodile. Trdclii/xanrns has pdor powers of 

 progression, its limbs being small and its neck undeveloped. It is an 

 interesting animal because it s'hows the early stages of the migration 

 of the heart from the gill-area to the thorax, during which migration 

 the left recurrent laryngeal nerve is caught about the aorta and 

 dragged into the thorax. 



The Tuatara lizard, S^/henodon pniirtatus, shows partial suppres- 

 sion of the ribs of its neck, therein agreeing with that rib suppression 

 which is seen in the more common lizard. 



Voranus varuis is as active a lizard as Trarln/s(iurii< riKjosux is 

 sluggish. It has a long neck containing six cervical vertebrae ; its 

 heart has left the pectoral girdle and become an occupant of the 

 thorax, and its pectoral girdle shows signs of atrophy. In the croco- 

 dile the pectoral girdle undergoes further atrophy, and tlie posterior 

 portion is retained to form the coracoid bones. The narrowing which 

 the girdle undergoes, in being tiansfonued into the coracoids, enables 

 the seventh vertebra to perform neck mavements ; and thus the 

 seven cervical vertebrae that iliaractcrisc the mauimaban necis, ai-e 

 established. 



This is a critical time in the evolution of the mammalian neck, 

 for at this stage the l)()dy is elevated for raised (piadrupedal pro- 



