DE. J. MUEIE OS THE FOKM AND STEUCTUEE OF THE MANATEE. 143 



elements of the latter are very distinct. The exoccipital (Eo) is in two subquadrate 

 halves widely apart, the foramen magnum (f?n) 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 (Bs) ; and behind them the membrane of the considerable-sized Eustachian sac is 

 left intact (fig. 17, Eus). The palatines (PI), maxillae (Mv), prfemaxillaj (Pm.v), and 

 jugal bones (Ju) 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 foetal skeleton. 



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. 



IV. The Muscular 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 manner 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 



' Loc. eit. p. 34. ' Kecueil de Myologie, plates 272 to 295. ^ Phil. Trans. 1868, p. 218. 



VOL. viiL — PART III. September, 1872. 2 



