SKELETON OF BEG-ALECUS ABG-ENTEUS. 21 



gently curved, transverse process (tr.p. 1), nearly If inch in length, which passes at 

 first upwards, and slightly backwards and outwards, and then almost directly backwards, 

 nearly in contact with the succeeding vertebra?, and ending at about the middle of the 

 fifth. The presence of transverse processes to the atlas is quite unusual. 



The second vertebra is, as stated above, almost double the thickness of the atlas ; its 

 centrum (c. 2) has five strengthening ridges on each side. The neural process is given 

 off from near the anterior end of the neural plate, the posterior end of which is 

 produced into a small, somewhat triangular process, which functions as a posterior 

 zygapophysis (p.zy). There is no transverse process. 



The third vertebra has well-developed transverse processes (tr.p. 3) springing from 

 the two uppermost of its strengthening ridges, and passing almost horizontally back- 

 wards. The neural processes now spring from near the centre of the neural plates, and 

 there are anterior as well as posterior zygapophyses developed from the extremities of 

 these plates. 



The fourth to the seventh vertebra closely resemble the third : they increase pro- 

 gressively in all dimensions save the thickness of the neural spine, which is reduced in 

 the seventh to about -£q inch, this thickness being now retained through the whole 

 column. The transverse processes are gradually inclined downwards, and from the 

 fifth vertebra onwards spring from the second and third of the lateral radiating 

 lamellae or strengthening ridge ; at the same time the zygapophyses undergo a con- 

 siderable increase in size, becoming high triangular processes. 



The eighth vertebra differs from its predecessors in possessing ribs (r. 8), slender 

 bony rods attached along the whole posterior edge of the transverse processes, and 

 projecting about \ inch beyond them, the total length of the ribs being about 

 \\ inch. 



In the succeeding vertebras the transverse processes become attached lower and lower 

 down on the sides of the centra, springing in the thirteenth from the third and fourth 

 strengthening ridges : they also become turned more and more directly downwards, 

 and at the same time increase in width, becoming flat subtriangular plates. The 

 ribs also increase in length, attaining their maximum in the eleventh vertebra, in which 

 they are If inch long, and project \\ inch beyond the end of the transverse process. 



In the twenty-first vertebra, only four strengthening ridges can be made out on each 

 side, the third being very poorly developed. The transverse process still springs from 

 the third and fourth, but mainly from the latter, which has now begun to take on the 

 characters of a haemal plate : the hinder end of the latter is produced downwards into 

 a triangular process (see fig. 22, n.pl 1 ), having much the character of a posterior haemal 

 zygapophysis. In the twenty -second the ribs have become greatly reduced, and appear 

 for the last time in the twenty-fifth, so that there are altogether eighteen (eighth to 

 twenty-fifth vertebras inclusive) pairs. In the twenty-third the zygapophyses are 

 poorly developed, and in succeeding vertebras they gradually disappear. 



In the twenty-seventh vertebra the dimensions of the haemal plate are markedly 



