('ert'icid Ribs in Man. 97 



atavism were a real thing in relation to ribs and other bones, the 

 tlyinfj-fox should have coracoid bones. 



Marine Mammals. — The New Zealand dolphin has had the bones 

 of its neck fused into a short, solid mass by impulses engendered by 

 the impact of water on tlie head, which is driven against the water 

 l)y the force exerted by the tail. This animal does not emerge from 

 the sea. and consequently it has entirely abandoned quadrupedal gait. 

 Tlie mammalian character of its neck has been destroyed by the fish- 

 like impulses that its acquired habits have set up. The Su.iue has 

 seven Hattened neck bones that occupy verA- little sjiace. On the 

 second, third, fourth, fifth and sixth cervical vertebrae the costal 

 processes are widely separated from the transverse processes ; on the 

 seventh there are no costal processes, but the head of the first rib 

 articulates with the body of the seventh vertebra, and its tubercle 

 with the transverse process of the first thoracic verteljr.i. A similar 

 arrangement to this occurs in the Beluga Whale. 



Seals, sea-lions and walruses form an interesting class of sea 

 mammals. Their necks are- long, and they are true to nuimmalian 

 neck type, and this is due to these animals using their fore-limbs to 

 lift themselves out of the water, and also to their liabit of travelling 

 over the rocks after the manner of quadrupeds. 



At the end of the long neck of the seal are well-developed fore- 

 limbs. At the end of the shortened neck of the New Zealand dolphin 

 is an atrophic pair of fore-liml)s. This association of structure sug- 

 gests that as the limbs descended the neck, during the evolution of 

 limb progression, a gradual increase in the size of the limbs took 

 place ; and as the limbs recede up the neck, as quadrupedal progres- 

 sion is abandoned, and the upper part of the pectoral limb is pro- 

 jrressively less used, the limbs progressively become smaller as they 

 approach nearer and nearer to the head. Thus not only can the 

 evolution of the neck be studied, but it is also possible to study the 

 involution of the neck. 



The seals demonstrate more plainly than any other nuunmals the 

 effect of quadrupedal progression on struct\ire ; for there can be no 

 doubt that the long neck of the seal handicaps its progress through 

 the water, though the neck is retained for the functions it performs 

 on the land. 



The order Sirf/nd offers a valuable mass of material bearing on 

 cervical ribs. The following quotations are from Flower's Osteology 

 of Mammalia, 1885, p. 42: — 



" In the order Sirenia the Dugong (Halicore) has seven cervical 

 vertebrae." 



" The Rhytina, a large animal of this order, which became extinct 

 towards the close of last century, has also seven cervical vertebrae, 



and the Miocene halitherium had also the same number." 



s 



