J. Wyman on the Ne-hoo-le. AT 
groove on its inner surface and all the roots are quite divergent. 
The transverse diameters of the anterior and posterior ridges are 
more nearly equal than in the other species. 
M. Senegalensis.—Molars %%,; the enamel is rugous; the 
inner root is not grooved, all of the roots nearly vertical, and 
the teeth in use not more than four. .M. datirostris. Molars 
t# +#, teeth in use four or five; enamel] rugous. M. Americanus, 
Molars 11.41, Teeth much smaller than in the preceding spe- 
cies; the number in action six. The crowns are higher, but the 
inner root as in M. nasutus is grooved on its internal surface. 
Il. Palate—The median ridge is flattened on its summit 
and the palatine foramina are of variable sizes; the most ante-— 
rior is the largest and perforates the bone nearly vertically and 
with rounded edges. In the M. /atirostris they are ail more 
minute; in the M. Senegalensis and M. Americanus, the ante- 
rior are the largest, but perforate the bone obliquely and are pro- 
tected for some distance after they assume the horizontal direction 
by a thin sharp edge or shelf of bone. The yalatine foramina 
are subject to so great variety in most animals, that the characters 
Just enumerated must be regarded as of doubtful value unless veri- 
€d on a large number of crania. 
Ill. Malar bones.—These are readily distinguished from the 
corresponding bones of all the other species in being very broad 
in their zygomatic portion, measuring nearly an inch in breadth 
at their free extremity. In M. Senegalensis, the zygomatic 
Portion is slender, style-shaped, and terminated by a knob. This 
is also the case in M. Americanus and latirostris, except that in 
the last the part in question has no enlargement at its ‘end, is a 
little broader than in the preceding, but forms a much closer union 
with the zygomatic portion of the temporal bone, approaching a 
Suture of the kind called “ harmonia.” 
- Frontal region.—In this as well as in M. Americanus the 
frontal region is quite narrow, but in the latter it is rounded, 
“bombée,” while in the former it is depressed. The forehead 
of the M. latirostris and Senegalensis is proportionally much 
broader. 
- Occipital foramen.—In all the species this foramen is more 
or less triangular, the angles being rounded ; but in M. America- 
nus, Senegalensis, and latirostris the apex is directed downwards, 
While in that from the Cavalla river it is directed upwards. 
The number of known species of the genus Manatus now 
amounts to four, two from Africa, viz.: M. Senegalensis and 
- nasutus, and two from the New World, viz. : M. Americanus 
M. latirostris. 
