462 DE. H. WOOD WA ED OJT AN ALMOST 



Barlow (the formatore of the Geological department) discovered 

 the three auditory ossicles still within the cavity. They agree very 

 closely with the figures given by Brandt *, and are also near to the 

 ossiculse auditus of the Manatee. 



The Stapes. — The stapes is a short columella-like bone, flattened 

 at each end, having a small perforation (which may perhaps indicate 

 the remnant of a much larger opening, the stirrup, observable in 

 this bone in some other mammalia). It fits at one end into the 

 fenestra ovalis, and unites at the other with the end of the incus. 



The Incus. — The incus is longer and stouter, and the superior and 

 inferior faces are depressed, and the posterior process, the long cms, 

 which articulates with the stapes, is shorter than in the Manatee 

 and Dugong. 



The Malleus. — The body of the malleus is much swollen, more so 

 than in the Dugong ; the superior face is convex, not depressed, as in 

 Manatus latirostris. The external process of the malleus has a 

 straight internal border (not arched as in Manatus) ; the external 

 border is strongly arched (not truncated below) ; the external face is 

 greater in breadth and is flatter than in Manatus. The condyles, 

 articulating with the incus, are bilobed and depressed. 



Bones of the Scapular Arch and Fore Limb. — The sternum has been 

 figured by Brandt f. It is a much stouter and stronger bone than 

 in the Manatee, but is similar in form. 



Scapula. — The scapula is somewhat convex externally, the inner 

 concave face fitting closely against the anterior ribs to which it was 

 applied ; the spinous process of the scapula is strongly developed. 

 The glenoid cavity is deep and circular and well fitted to the rounded 

 head of the humerus ; the humerus is short and stout ; the radius 

 and ulna, which are also short, are anchylosed together at both 

 extremities and incapable of any rotatory motion ; the olecranon is 

 strongly produced and curved, showing that the fore arm as well as 

 the humerus had considerable free lateral movement for the act of 

 swimming. 



The Manus. — The carpal bones and digits are unknown in 

 JRhytina ; the digits were probably five, as in Manatus and Halicore 

 (but the thumb in the latter is rudimentary). Externally viewed 

 the fore limbs in Bhytina were fin-like, with no external digits or 

 nails visible ; but Steller describes their extremities as thickly 

 covered with short bristly hairs. 



Density of Skeleton. — The skeleton is remarkable for the 

 massiveness of the bones, especially the great density of the ribs, 

 which have the hardness of ivory. There is a geueral absence of 

 medullary cavities in the bones. 



The great specific gravity of the bones no doubt assisted these 



* See also Claudius " On the organs of hearing in Bhytina,'" Mem. Acad. 

 Imp. Sci. St. Petersbourg, 1867, vol. xi. no. 5, 2 plates ; Brandt, " Symb. Siren." 

 Faso. ii. pp. 8-10, Tab. ii. figs. 11-20. Mem. Acad. Imp. Sci. St. Petersbourg, 

 ser. vii. 1861. 



t I believed we also had in the Museum an imperfect sternum of Bhytina, 

 and Prof. Flower, after comparison, agrees in this determination. 



