DR. J. MUEIE ON THE FORM AND STRUCTURE OF THE MANATEE. 201 



within the chevron bones ; L.Rete, lumbar vascular rete shown in part ; Be, brain- 

 cavity ; n.ch, nasal chamber leading by narrow canal to n, external narial orifice ; 

 Pmx, premaxillary bone in section, covered by the fleshy, fibrous snout ; sy, mental 

 symphysis; ul, upper lip ( = outer); ^lp, upper pad (=inner lip); II, lower lip 

 (=outer); Ip, lower pad ( = inner lip); hh, buccal hairs; T, tongue; Eus, orifice 

 of Eustachian tube ; Sgh, stylo-glossus and hyoid muscle ; a double-headed arrow 

 beneath leads from the fauces to the oesophageal and laryngeal passages, each 

 partially laid open ; la, cut larynx ; oe, oesophagus ; Rete &c, portion of rete cervicale ; 

 J& C, jugular vein and carotid artery severed ; M<& F, muscle and fat between the 

 fore limbs ; cv, cervical vertebrae. 



Fig. 38. Front segment of the skull, showing the nasal cartilage on the right side, and 

 the open nares, diminutive nasal bone, &c. on the left. 



Ir, frontal bone ; Na, left nasal ; Tu, turbinals ; 0, right orbit ; nc, nasal cartilage ; 

 sp, septal cartilage ; cf, cartilaginous fissure ; Px, infraorbital plexus of arteries. 



Fig. 39. A transverse section of the tail behind the anal constriction, but in advance of 

 the caudal expansion. It shows : — c, centrum of a vertebra, its articulating 

 surface surmounted by the neural ai'ch (a) enclosing the spinal cord, which 

 is surrounded by a vascular plexus ; t, cut surface of transverse process, 

 between which and centrum is another rete mirabile ; ch, lamina of chevron 

 bone enclosing subcaudal rete ; Ld, Lee, levatores caudse internus and ex- 

 temus or continuation of the dorsal muscles ; L.e, lumbo-caudalis ; Sc and 

 If.c, sacro-coccygeus and infra coccygeus, lower tail-muscles ; Sk, skin, fatty 

 fibro-fatty layer, &c. 



Fig. 40. A cross section of the flat expanded tail : vt, vertebra ; t\ levator caudal tendons, 

 and f, depressor caudal tendons surrounding the bone ; f, fatty and fibrous 

 tissue, containing the open mouths of nourishing vessels ; sk, skin, its fibroid 

 subdermal layer, covered by a black line representing the derm and cuticular 

 covering. 



Fig. 41. A portion of the root end of the lung, with its vessels minutely injected: 

 £, bronchus ; hh, bronchia ; v, pulmonary vein, and a, artery ; I, lobule. 



Fig. 42. The right eyeball, mesially and vertically divided, and posteriorly other orbital 

 contents. Parts about natural size, and from the female Manatee. 



O.Rete, orbital vessels ; m, muscles ; on, optic nerve ; ion, infraorbital nerves ; ca, ciliary 

 artery ; sc, sclerotic ; cp, ciliary processes ; I, lens. 



Fig. 43. A transverse section of the same eye behind the ciliary processes and iris. 

 Fig. 44. A ventral view of the female body eviscerated and dissected, chiefly to show 



the long tendinous diaphragm and kidney thereupon, the intercostal vascular 



plexuses, and the lumbo-caudal muscles. 



