DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 143 
elements of the latter are very distinct. The exoccipital (Zo) is in two subquadrate 
halves widely apart, the foramen magnum (fm) being surrounded by membrane and 
fibroid tissue. The basiocciput (Bo) is free, its basisphenoid articulation, as in older 
animals, being unossified. Each alisphenoid (As) is disconnected from the basisphe- 
noid (#s); and behind them the membrane of the considerable-sized Eustachian sac is 
left intact (fig. 17, Zus). The palatines (P/), maxille (Mx), premaxille (Pm), and 
jugal bones (./w) have their lines of approximate union very marked; how many ossific 
centres each had I did not note. In the adult, at the outer posterior angle of the orbit, 
a bony process is sent up from the jugum; this is a sesamoid or separate ossific 
element (s) in the fcetal skeleton. q 
In the above foetus, on each side, a pair of spaces indicated the future molars in their 
saccular condition, and a tiny orifice a premaxillary incisor. In our Society’s specimens 
with difference of age the same conditions obtained, viz. five grinding-teeth in use and a 
sixth almost erupted, whilst in the cavity behind there was evidence of at least three 
more in an undeveloped state. Minute denticles representative of a pair of upper and 
lower incisors I distinctly detected. 
LV. Tue Muscunar System. 
To my knowledge Stannius is the only author who has treated of the myology of the 
Manatee’; and his descriptive remarks are chiefly confined to a very general account of 
the abdominal and caudal muscles. These he has compared with those of Cetaceans, 
taking the Common Porpoise as his type. He briefly points to certain resemblances 
between the tail-muscles of the two, shows that the cutaneous panniculus, the muscles of 
the abdomen, and the so-called psoas muscles differ in the one form and in the other. 
But the restricted mauner in which he traces the homologies, and the fact that he has 
left unnoted the muscularly clad anterior extremity, the extraordinarily developed facial 
muscles, and the large deep muscles of the otherwise shortened neck, render it 
desirable that further demonstration of the fleshy structure of this singular mammal 
should be placed on record. 
The Manatee’s pseudo-Whale-characters (herbivorous Cete of the Cuviers and others) 
and Gravigrade tendencies (of Blainville) cause me to compare its myology respectively 
with Whales and the Elephant. Laurillard’s’ superb delineations serve well my purpose 
for the latter; Stannius’s, Carte and Macalister’s*, and my own dissections of Cetacea 
abundantly supply me with material for the former. 
1. Muscles of the Axial Skeleton. 
(A) Those connecting the Spinal Column.—Dorsal Aspect.—I shall take the deep 
fleshy and tendinous bundles upon the dorsal surface of the spine as the starting-point 
whereon to build up the muscular structure incorporating the soft frame of the 
1 Loc. cit. p. 34. ? Recueil de Myologie, plates 272 to 295. 5% Phil. Trans. 1868, p. 218. 
VOL. VIII.—PART 11. September, 1872. Z 
