469 



2640. A posterior rib of the same side of the same Halicore australis, showing a 

 similar but more developed projection from the posterior margin, a little lower 

 down. Presented by J. B. Jukes, Esq., F. G.8. 



2641. A rib of the same Halicore australis, with the posterior process more de- 

 veloped. Presented by J. B. Jukes, Esq., F. G.S. 



2642. A pair of ribs of the same Halicore australis, showing the same peculiar pro- 

 cess from the posterior margin nearly half-way down the rib. 



Presented by J. B. Jukes, Esq., F.G.S. 



2643. A more posterior pair of ribs of the same Halicore australis, with the posterior 

 process in the same position. Presented by J. B. Jukes, Esq., F. G.S. 



2644. A rib, longitudinally bisected, of the same Halicore australis. The posterior 

 processes in this and the foregoing specimens resemble the anchylosed 

 appendages of the same part of the ribs in birds. 



Presented byJ. B. Jukes, Esq., F.G.S. 



2645. The right and left scapula of the Halicore australis. 



Presented by J. B. Jukes, Esq., F.G.S. 



2646. The petrotympanic bone and two of the otosteals, viz. the malleus and incus, 

 of the Halicore australis. Presented by J. B. Jukes, Esq., F.G.S. 



Genus Manatus. 



2647. The skeleton of a young female Manatee (Manatus americanus). 



The two deciduous incisor teeth of the upper jaw are shed, and a section of the right pre- 

 maxillary shows the absence of any germ of a permanent one. The alveoli of the molar teeth 

 are gj^g, of which the last one on each side in both jaws contains the germ of a tooth. The 

 atlas and axis are not anchylosed together ; only four distinct neural arches intervene between 

 these and the dorsal vertebrae, or those supporting moveable ribs, of which there are 17 pairs. 

 The twenty-fifth vertebra bears short pleurapophyses articulated to its transverse processes ; 

 the transverse processes of the remaining 25 vertebrae are long, but progressively diminish, 

 and are, at last, mere tubercles. The twenty-ninth vertebra begins to support haemapophyses 

 and indicates the commencement of the caudal region. The neurapophyses of the first twenty- 

 nine vertebrae are joined by suture to their respective centrums. 



Presented by Sir Everard Home, Bart., V.P.R.S. 



