1889.J MR. W. K. PARKER ON STEATORNIS CARIPENSTS. 173 



arljiculate with it, and the distal free end is narrow, terete ; it is 

 ossified, proximally, by a separate centre. The posterior cornua 

 are 31 millim. long; they are feeble, rather straight, and the upper 

 piece, which is 11 millim. long, has its distal half cartilaginous. 



III. The Vertebral Chain and Ribs. 



The vertebral formula of this bird is as follows : — C. 15, with .3 

 pairs of ribs, free, on tlie left, and 4 on the right side ; D. 4 ; S. 13, 

 the first with large free ribs, this and the next two, with arrested 

 ribs, buttress the pre-ilia; the 13th vertebra not firmly ankylosed 

 to the 12th ; Cd. 7 + 4 or .5, = Total 43 or 44. 



The procoelous articular facet of the atlas (Plate XIX. fig. 1, at.) 

 is somewhat transverse, and this cup is largely notched for the 

 odontoid process of the axis (Plate XVIII. fig. 3) ; not perforated 

 as in most of the high arboreal birds. The atlas has no lateral 

 passages for the vertebral artery ; its centrum articulates with the 

 axis by the norm&\ fiat facet. The odontoid process of the axis is 

 large (Plate XVIII. fig. 4) ; this bone (Plate XIX. fig. 1, ax.) has 

 thick, blunt upper and lower spines, and oldi4ue ascending snags over 

 the post-zygapophyses ; a pair of small upper /e«e«<r<K, and, what is 

 very rare in birds, vvell-fornied rib-bars (c)-'.) to enclose the canal for 

 the vertebral artery ; the articulation of the centra throughout the 

 rest of this region is cyllndroidal. The 3rd cervical (Plate XIX. 

 ,fig. ] ) has also blunt upper and lower spines, lateral fenestrse, above, 

 a wide top, and a definite snag over each post-zygapophysis, and a 

 rudimentary rib, right and left, bounding tlie canal for the vertebral 

 artery ; this part is 3-.5 millim. long. 



The 4th cervical (Plate XIX. fig. 1) has its sides notched, not 

 fenestrate; it has both upper and lower spines, somewhat larger 

 riblets, and spines on the post-zygapophyses. 



The 5th cervical is much like the next four or five ; but in this 

 strong chain of bones each succeeding vertebra is larger and stronger 

 than the one in front of it ; towards the chest they become shorter, 

 as well as wider. This .5th bone, hke the rest up to the 12tb, has 

 large riblets ; on the .5th, 6th, and 7th these styles reach back 

 within 2 millim. of the end of the centrum. None of these vertebrae 

 have the inferior or carotid canal developed, for the inferior face is 

 wide open and gently concave in front ; at the middle they are sub- 

 carinate, and flat behind, where they broaden out into the apparently 

 convex, but really concave, hinder facet. The wide canal for the 

 vertebral artery, right and left, is only complete in the front third of 

 each vertebra, and only on the 10th, llth, and 12th is there any 

 rudiment of the oblique bar (or flying buttress) so common in the 

 Coccygomorphse, a growth that partially finishes the lateral bony 

 wall. I have mentioned that the 3rd has large lateral lioles above, 

 and that the 4th is notched, and not fenestrate. The 5th also is 

 notched on its outer and upper edge ; but the hinder margin of each 

 notch is developed into an oblique, bony bar, which, running 

 forwards, inwards, and upwards, forms by union with its fellow a 



