468 



2634. The skull of a female Australian Dugong (Halicore australis). 



From the non-protrusion of the upper incisive tusks, the extremities of which are obtusely 

 pointed, and from the open state of their alveoli, this specimen may be concluded to have 

 belonged to a female. It is of full size and mature age, the molar teeth being reduced to 

 three in number on each side of both jaws. The petrotympanic bones are preserved. The 

 alveoli of the abortive incisors of the lower jaw are four in number on each side of the long 

 sloping symphysis. There are two perforations in the middle line of the parietal bones. 



The specimen to which this skull belonged was taken in Port Essington, North Australia. 



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



2635. Most of the bones of the cranium of the Australian Dugong (Halicore au- 

 stralis). 



The chief distinction between this and the Indian species is here seen in the presence of an 

 additional alveolus at the beginning of the molar series, on each side of both jaws, making 

 the total number of these teeth, developed in the Halicore australis, 24. The series is 

 arranged in a stronger curve, with the convexity outwards in the upper jaw. The falciform 

 ridge of the coalesced parietals is much sharper in the present species. The pterygoid pro- 

 cesses of the sphenoid are more deeply excavated posteriorly, and the true pterygoid bones 

 are thicker. The sockets of the deciduous incisors are relatively deeper ; those of the germs 

 of the permanent incisors are exposed externally at their base, indicating the specimen to be 

 afemale. In the lower jaw, the third sockets of the incisors, counting from below, are much 

 deeper than the rest, showing that they have lodged normally developed teeth. 



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



2636. A penultimate molar tooth of the Halicore australis. 



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



2637. A last molar tooth of an old Halicore australis, wiin a small tumour of cement 

 at one margin of its base. Presented by J. B. Jukes, Esq., F.G.S. 



,2638. An upper incisive tusk of a female Halicore australis, showing the oblique 

 position and tumid border of the shallow and almost obliterated pulp-cavity. 



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



2639. One of the ribs of the Halicore australis. It has a rudimental tubercle about 

 one inch and a half from the head : there is a slight projection from the poste- 

 rior margin, three inches below the tubercle. 



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



