SKELETON OF PROBOSCIDIA. 437 



for slenderness and oily porosity of texture. Although the bones 

 of the pectoral limbs are swathed in skin, the fins project more 

 freely from the trunk, the elbow is better marked ; the limb-joints 

 are synovial, not syndesmotic merely, as in Cetacea ; and although 

 there are clearer indications of the digits in the fin of Sirenla, 

 none of the digits have more than three phalanges. 



§ 186. Skeleton of Proboscidia. — With the exception of a very 

 small cavity in the femur and tibia, a light cancello-reticulate struc- 

 ture occupies the centre of the long bones, which have tliick and 

 compact osseous walls. The skull-bones are extensively pneumatic. 



A. Vertebral Column. — In the giant mammal of the land, as in 

 that of the sea, the neck is short, and through loss of length, not 

 of number, of the cervical vertebrae. In the Indian Elephant, 

 fig. 162, the vertebral formula is: — 7 cervical, c, 20 dorsal, d, 

 3 lumbar, 3 sacral, and 31 caudal. Anapophyses are developed 

 from the sixteenth dorsal, and articulate with metapophyses from 

 the seventeenth. The same joints are superadded to the ordinary 

 articular processes, as far as the last lumbar. Five pairs of ribs 

 directly join the sternum, which consists of four bones. The 

 epiphyses continue detached from the bodies of the vertebrae to 

 nearly full growth. 



In a half-grown Elephant, the neurapophyses of the atlas are 

 distinct from the hypapoj)hysis, and united to each other above by 

 suture : the centrum is also distinct, but attached to that of the 

 axis, of which it forms the * odontoid ' process. The neurapophyses 

 develope both upper and lower transverse processes, which circum- 

 scribe the vertebrarterial foramen. The same is the case with the 

 neurapophyses of the axis, which blend together above and de- 

 velope a thick bifurcate spine before coalescing with the centrum. 

 The removal of the terminal epiphyses of the short flat bodies of 

 the other cervicals shows that the upper fourth of the body is 

 contributed by the neurapophyses, the rest by the centrum. In 

 the fifth cervical vertebra, a short and slender spine is developed 

 from the summit of the neural arch. The antroverted costal part 

 of the transverse process is connate with the par apophysis, and 

 afterwards coalesces with the diapophysis. In the seventh cervical 

 vertebra, the transverse processes consist of diapophyses only. 

 The articular surface for the head of the first free or dorsal rib is 

 formed, half by the neurapophysis, and half by the centrum. The 

 neural spine has much increased in length, but is slender. 



The first dorsal vertebra is remarkable for the strenojth as well 

 as the height of the neural spine. The diapoj^hyses are shorter 

 and thicker than in the neck. The surfaces for the first and 



