200 DR. J. MURIE ON THE FORM AND STRUCTURE OF THE MANATEE. 
nium; a, anterior commissure; c‘, corpora quadrigemina; v*, fourth ventricle; 0°, 
fifth ventricle. 
Lobes of cerebrum :—F, frontal; P, parietal; 7, temporal; O, occipital. 
Fissures, or sulci:—sy, sy', sy’, Sylvian; if, infero-frontal; mf, midfrontal; sf, supero- 
frontal; ap, antero-parietal; 70, Rolando, or postparietal ; op, occipito-parietal ; of, 
occipito-temporal ; ca, calcarine ; cm, calloso-marginal. 
Folds or gyri:—Jo, interorbital; d/o, 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; P#, posttemporal; Soc, Supraoccipital ; 
Moc, midoccipital; Joc, infero-occipital; U, uncinate; Ma, marginal; C, callosal. 
Cerebellum :—av, arbor vite; sv, superior vermiform process or middle lobe; 7, 
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.; 5, perforation transmitting third and fourth nerves &e. ; 
5 & 7, foramina respectively for trigeminal and auditory nerves &c.; ca, carotid 
groove; t, temporo-sphenoidal fossa; P, pituitary fossa; 7, jugular groove ; pa, plexus 
and lateral sinus; pa*, spinal plexus. 
Lettering of right half:—J/r, frontal bone; JM/a, maxillary; Os, orbito-sphenoid ; As, 
alisphenoid; Bs, basisphenoid; Bo, basioccipital; Ho, exoccipital; Sq.d-Pa, squamo- 
parietal; P, periotic; 7, tympanic; 2*, optic groove; 7 
Sc’, superior semicircular canals ; c, ¢*, condyles. 
; meatus auditorius internus; 
PLATE XXVI. 
Fig. 37. Longitudinal and partly median section of the body, head, &c., of the young 
male Manatee, 4 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 D, D, D, D, D*, the lengthened horizontal dia- 
phgram ; /sf, ligamentum subflavum of dorsal vertebre; f, coating fat and skin of 
the back; H, heart; St, stemum; J, liver; Sto, stomach; J, folds of intestine; 
B, urinary bladder; P, penis within its sheath; Rab, rectus abdominis and cut 
fleshy wall; B.c, bulbous cavernosus muscle; Jev, ischio-cavernosus; Sp.a, sphincter 
ani; A, anus; Js.c, ischio-coccygeus; Se+Tf.c, sacro-coceygeus 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 ; P/, pelvic bone; Pf, pelvic 
suspensory fascia; C.Rete, the rete mirabile which proceeds to the end of the tail 
