200 DE. J. MUEIE ON THE FORM AND STETICTTJRE OP THE MANATEE. 



nium ; a, anterior commissure ; c*, corpora quadrigemina ; v*, fourth ventricle ; v^, 



fifth ventricle. 

 Lobes of cerebrum : — F, frontal ; P, parietal ; T, temporal ; 0, occipital. 

 Fissures, or sulci : — sy, sy^, sjf. Sylvian ; if, infero-frontal ; mf\ midfrontal ; sf, supero- 



frontal ; ap, antero-parietal ; ro, Eolando, or postparietal ; op, occipito-parietal ; ot, 



occipito-temporal ; ca, calcarine ; cm, calloso-marginal. 

 Folds or gyri : — lo, interorbital ; Mo, midorbital ; Eo, entorbital ; If, infero-frontal ; 



Mf midfrontal; Sf supero-frontal ; Ap, antero-parietal {premier pli ascendant); 



Pp, postparietal {second pli ascendant) ; Lob, lobule of postparietal ; Ang, angular ; 



At, antero-temporal ; Mt, midtemporal ; Pt, posttemporal ; Soc, Supraoccipital ; 



Moc, midoccipital ; loc, infero-occipital ; U, uncinate ; Ma, marginal ; C, callosal. 

 Cerebellum : — av, arbor vitse ; sv, superior vermiform process or middle lobe ; fl, 



flocculus ; ag, amygdaloid lobe. 



Fig. 36. Portion of skull of female Manatee, with calvarium removed to show interior base. 

 The dura mater is in place on the left moiety, but cleared away on the right. 



Lettering applicable to the left half: — 1, olfactory fossa; 2, foramen piercing mem- 

 brane for optic nerve &c. ; 3, perforation transmitting third and fourth nerves &c. ; 

 5 & 7, foramina respectively for trigeminal and auditory nerves &c. ; ca, carotid 

 groove ; t, temporo-sphenoidal fossa ; P, pituitary fossa ; j, jugular groove ; px, plexus 

 and lateral sinus ; px*, spinal plexus. 



Lettering of right half: — Fr, frontal bone; Mx, maxillary; Os, orbito-sphenoid ; As, 

 alisphenoid; ^s, basisphenoid; ^o, basioccipital ; iJo, exoccipital ; <S'j.c&P«, squamo- 

 parietal ; P, periotic ; T, tympanic ; 2*, optic groove ; 7, meatus auditorius internus; 

 S(f, superior semicircular canals ; c, c*, condyles. 



PLATE XXVI. 



Fig. 37. Longitudinal and partly median section of the body, head, &c., of the young 

 male Manatee, ^ nat. size. The ribs are left in position, but dissected so as 

 to show the remarkable relations of the lungs, diaphragm, and viscera 

 generally. 



L, L, L, L. L*, the lung resting on B, D, P, B, B*, the lengthened horizontal dia- 

 phgram ; hf ligamentum subflavum of dorsal vertebi-se ; f, coating fat and skin of 

 the back ; H, heart ; St, sternum ; Li, liver ; Sto, stomach ; /, folds of intestine ; 

 B, urinary bladder ; P, penis within its sheath ; Bab, rectus abdominis and cut 

 fleshy wall; Be, bulbous cavemosus muscle; /ct, ischio-cavernosus ; Sp.a, sphincter 

 ani ; A, anus ; Is.c, ischio-coccygeus ; Sc+If.c, sacro-coccygeus and infra-coccygeus, 

 obliquely cut through ; fc, fibrous caudal expansion with a rim of the skin left ; but 

 on the opposite right side the skin has not been removed ; PI, pelvic bone ; Pf, pehic 

 suspensory fascia ; CBete, the rete mirabile which proceeds to the end of tlie tail 



