467 



2630. A molar tooth, vertically bisected, and with the cut surfaces polished, of a 

 Malayan Dugong (Halicore indicus). 



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



2631. A polished transverse section of a molar tooth of a Malayan Dugong (Hali- 

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



2632. The skeleton of a female Australian Dugong (Halicore australis). 



The deciduous incisive tusks of the upper jaw have not been shed : the permanent ones, 

 of which the left is exposed in the formative socket, are about four inches in length : the 

 outer wall of the base of the socket has been removed by absorption, as is usual in the female 

 sex. There are four molars, and a small vacant socket anterior to them on each side of both 

 jaws : the last molar had just begun to cut the gums. The pleurapophyses are absent, or 

 have not been ossified in the second, third, fourth and sixth cervical vertebrae, the transverse 

 processes of which are accordingly notched, not perforated, by the vertebral artery. The 

 neurapophyses of the fourth and fifth cervicals have not coalesced above. There are 19 

 dorsal vertebrae : the first three pairs of ribs join the sternum : a strong process bends for- 

 wards from the under part of the neck of the first rib. From the third to the nineteenth 

 vertebrae the ribs are of nearly equal length. 31 vertebrae succeed the dorsal. The pelvic 

 bones are suspended to the fifth of this series. Two detached haemapophyses are attached 

 to the sixth, and a second pair to the interspace between the sixth and seventh of these ver- 

 tebrae. The haemapophyses coalesce at their lower extremities to form chevron bones, which 

 are articulated to the interspaces of the succeeding vertebrae as far as the fourteenth. The 

 pelvic bones consist of a long and slender rib-like ilium, coalesced with a similar but shorter 

 ischium, and seem to have been loosely attached at both ends. 



The specimen from which this skeleton was obtained was taken in Shark's Bay, North 

 Australia. 



Presented by Lieut. Helpman, R.N. 



2633. The skull of a full-grown male Australian Dugong (Halicore australis). 



The alveoli of the exserted tusks of the upper jaw are entire, as in the male of the Malayan 

 species ; but they are not quite so broad and thick in proportion to the length of this deflected 

 part of the jaw. The molars are reduced to the last two of the series on each side of both 

 jaws. The superoccipital has coalesced with the parietal, but not with the exoccipitals. The 

 incisive tusks are smaller, and the penultimate molars larger, than in the Malayan Dugong 

 (No. 2545). The median ridge of the deeply-grooved palate is less developed. The tym- 

 panics and otosteals are preserved in this skull. The alveolar disk of the sloping symphysis \ 



of the lower jaw is longer and narrower than in the Indian species. 



Purchased. 

 3o2 



