976 MB. W. p. PTCRAPT ON THE [DeC. 13, 



the dentary. The form of the dentary supra-angular suture has 

 been described in the adult (see p. 965). 



iv. The Veetebbax Column. 



The vertebral column is singularly uniform iu cliaracter 

 throughout the group. The cervicals are peculiar chiefly on account 

 of the great development of the metapophyses and hyperapophyses 

 of certain vertebrae. 



The thoracic vertebrae are opisthoccelous and somewhat closely 

 resemble those of Phalacrocorax, from which they may be distin- 

 guished by the great development of the styloid processes, seated 

 on the anterior border of the trausverse process midway between 

 the capitular articulation for the rib and the centrum. The 

 synsacral hypapophyses found in Phalacrocorax are absent in the 

 Penguins. 



The synsacrum is a dense bony mass which remains unanchy- 

 losed with the innominate bones throughout life. On a ventral 

 view, the lumbar swelling is seen to be very large. The outer ends 

 of the last thoracic and the first two lumbar vertebrte fuse together 

 to enclose a pair of holes on each side : behind, in the middle 

 of the lumbar enlargement, are seated a pair of short, thick 

 parapophyseal elements abutting against the ilium. The renal 

 fossa cannot be definitely separated into anterior and posterior 

 portions. The true sacral vertebrae are not, in very old specimens, 

 easy to make out : they are enclosed iu the hexagonal mass lying 

 opposite the acetabulum and ilio-ischiadic foramen. Three 

 vertebrae take part in the formation of this mass, of which the 

 2nd and 3rd represent the two prinoitive sacrals. From 1 to 3 of 

 the caudals may be included in the synsacrum, according to age. 

 None of the synsacral vertebrae bear hypapophyses. Dorsally, 

 the region of the synsacrum, between the hexagonal sacral mass 

 and the first pair of parapophyseal elements anterior to this, is 

 much expanded. In the complete pelvis this lies immediately 

 cephalad of the acetabulum. In the region behind this it is more 

 or less constricted. The synsacrum is composed of from 12-14 

 vertebrae. The pygostyle (PI. LXI. fig. 5) is composed of about 

 6 vei'tebrae, the neural spines of which run dix'ectly forwards and 

 parallel with the vertebrae and overlap tlie spine next in front. 

 The vei'tebrae cannot be generically distinguished. 



There are from 9-10 pairs of free ribs. The first two pairs 

 are those of the cervico-thoracic vertebrae. Of these, the first 

 takes the form of an elongated bony style; the second I'epresents 

 a complete dorsal rib, but has no sternal segment, and bears an 

 uncinate process. The remaining ribs increase in length and 

 slenderness from before backwards, and all but the last bear 

 uncinates. These, in the 1st to 4th ribs, are very long and broad. 

 There is frequently, perhaps always, an extra pair of sternal ribs 

 closely attached to the posterior border of the sternal segment of 

 the last thoracic rib. 



