SKELETON OF SIEENIA. 435 



tween this and the deflected symphysial part the lower border is 

 deeply concave : the sockets for the molar teeth, originally five 

 or six in number, like those in the maxillary, are reduced to two 

 or to one in the old animal : the deflected symphysis forms a flat 

 oval surface anteriorly, with four or five pairs of small alveoli, in 

 one or more of which may be an abortive incisor, fig. 160, «, d i 3, 

 covered by the thick horny plate attached to the flat rough sur- 

 face ; the dental canal, beginning in advance of the ascending 

 ramus, ends by a wide oblique opening from which channels 

 diverge on the outside of the deflected symphysis. 



In the Manatee, a large otocrane is also smoothly excavated in 

 the mastoid, squamosal, and exoccipital bones, to which the 

 petrosal closely fits without coalescence, its posterior surface ap- 

 pearing in the space left between the mastoid, super- and exoc- 

 cipitals. The basi-sphenoid coalesces with the alisphenoids, prior 

 to confluence with the basioccipital and presphenoid : the latter 

 similarly coalesces with the orbitosphenoids, and is continued, 

 like a rostrum, into the vomerine fissure. I find no distinct nasals 

 anterior to the frontal suture in the new-born Manatee ; nor 

 other representatives of them than the small amygdaloid bones, 

 fig. 239, 13, 13, articulated to the frontals at the posterior angles 

 of the nasal aperture : this is large, subrhomboid, horizontal. 

 The wide antorbital foramen is entirely surrounded by the maxil- 

 lary, ib. 26. The suborbital plate of the malar rests upon the 

 platform extending horizontally outward from above the anterior 

 molars, and extends the floor of the orbit an inch beyond the 

 roof, the eyeball resting upon the concavity of the malar, as on a 

 shelf. The zygoma, ib. 27, is unusually massive. The premaxil- 

 laries, ib. 2>, in the young Manatee, show a pair of alveoli for 

 abortive incisors : a similar pair imjDresses the fore part of the 

 mandibular symphysis, and a slight groove extends downward 

 from each. The symphysis is deeply hollowed out behind. The 

 coronoid is produced obliquely upward and forward; the angle of 

 the jaw is not marked. 



The ossified parts of the hyoid arch are the basihyal, fig. 294, a\, 

 stylohyals, 3s, and the thyrohyals, 43 : the ceratohyal, 40, is carti- 

 laginous : the arch is suspended to the angles between the mastoid 

 and paroccipital. 



C. Bones of the Limhs. — These are limited to the pectoral pair, 

 and their supporting arch is reduced to the scapula, with a short 

 coracoid as a tuberous process. The scapula, fig. 292, 5i, is sub- 

 longate, recurved, with the convex anterior costa continued into 

 the base, with an angle feebly marked in the Manatee. The 



F F 2 



