Hutton. — The Axial Skeleton in the Dinornithidce. 159 



bach be allowed. Of the correctness of the name Pachyomis 

 there can be no doubt. 



As the generic characters depend more on the axial than 

 on the appendicular skeleton, it follows that the species in 

 which the axial skeleton was first described must be taken as 

 the type of the genus, and not the species to which the generic 

 name was first applied, if the leg-bones only were known. 

 This is necessary to prevent constant changes. 



General Characters of the Vertebral Column. — So far as is 

 at present known, all the moas have fifty-six vertebrae. Of 

 these, 1 to 21 are cervical ; 22 to 24 are cervico-thoracic ; 25 to 

 27 are free thoracic, with sternal ribs articulating with the 

 sternum. No. 28 is sometimes free, sometimes attached to 

 the pelvic vertebrae ; both it and No. 29 have floating sternal 

 ribs. The pelvic (or syn-sacral) vertebrae are seventeen in 

 number, from 28 to 44. No. 45 is sometimes anchylosed to 

 those in front of it, sometimes free ; Nos. 46 to 53 are free 

 caudals ; No. 54 is sometimes free, sometimes anchylosed to 

 Nos. 55 and 56, which always form a single bone. The atlas 

 is broadly oval, the longer diameter dorsi-ventral. The bony 

 bridge for the vertebral artery is always strong. The post- 

 zygapophyses are well marked ; there is no trace of a neural 

 spine. The pre-axial articulating surface is crescentic, the 

 dorsal notch being very large.* It is much like the atlas in 

 Dromaius, and very different from that of Apteryx. 



The axis is comparatively short in an axial direction. The 

 neural platform is triangular, with a nearly straight posterior 

 margin. There is a deep pit behind the neural spme, and 

 well-marked hyperapophyses. The posterior articulating sur- 

 face is much elongated ventrad, and below it is a strong 

 hypapophysis. This bone also closely resembles that of Dro- 

 maius, and is very different from that of Apteryx. 



In the cervical vertebrae the centra increase in length to 

 No. 16 or 17, and are proportionally longest and narrowest 

 from 9 to 11. In Nos. 2 to 5 the hypapophysis forms a keel, 

 which becomes obsolete on No. 6. A pair of hypapophyses 

 spring from the ventral surface of the parapophyses in No. 6 ; 

 they increase in size in each posterior vertebra, and are 

 widest apart at No. 15 or 16. They then approach, and 

 coalesce into a median tubercle on No. 19 or 20. Dorsad, the 

 anterior cervicals, Nos. 3 to 6, expand into a quadrangular 

 neural platform, which is transverse in Nos. 3 to 5, nearly 

 square in No. 6. From this platform rises the neural spine, 

 always divided into two on No. 6, and usually so on Nos. 3 

 to 5. On No. 7 the two neural spines are continued post- 



* I have never seen an atlas resembling the one figured by Owen in 

 his Ext. Birds of N.Z., p. 392. 



