DE. J. MUEIE OX THE FOEM AXD STEUCTUEE OF THE MANATEE. 149 



upper nares, the greater amount going to the lip and and anterior infranarial region. 

 The latter are sent inwards in distinct transverse lines, more particularly the deep layer. 

 The section of this part thus resembles, on a small scale, the trunk of the Elephant 

 when cut across — the tissue intervening between the muscular bundles and fibrillse 

 being fatty and fibrous. 



Many vessels penetrate the root and origin of this levator ; this, no doubt, led Vrolik^ 

 to regard " the structure of the upper lip as plainly an erectile tissue." The true action 

 of this muscle here may most plausibly be assumed to be a dilater of the nares. 



Deeper than the last, is a broad and thick plane of muscle, which, issuing from 

 underneath the projecting orbit, proceeds forwards by parallel fleshy fibres, less broad 

 than the preceding. These wind round the anterior portion of the intermaxillary, and 

 lie above the buccinator, being inserted into the incisive fossa. The upper border of 

 this muscle, and its anterior portion, have apparently oblique fibres, which, being 

 difficult to dissect, are readily cut across, and have a coarse aspect. These are what 

 may represent the levator anguli oris, or be part and parcel of the combined levator 

 labii proprius and levator anguli oris — here, however, not clearly separable. 



I name more than define a depressor labii superioris alceque nasi a thick mass of the 

 deepermost fibres of the muscle just described, and partly continuous with the zygo- 

 matici. These may represent, in a modified manner, the muscle in question. It is not 

 at all clear or distinct, excepting by an alteration in the inner and narial fibres of these 

 muscles. It seems to constitute a muscular layer directly in front of the intermaxillaries, 

 stretching from the gum round the external aperture of the naris. 



The muscular layer the most superficial of those upon the muzzle, I take to be the 

 equivalent of the levator labii superioris alceque nasi. It is of considerable thickness and 

 great breadth, and almost throughout fleshy. Trapezoidal in figure, the four unequal 

 sides respectively form the medio-nasal, the orbital, the labial, and the muzzle boun- 

 daries. Fibres arise in a longish peaked manner from the outer side of the nasal 

 cartilage upon the superior maxillary bone ; thence they spread downwards and forwards, 

 part winding outwards round the orbit, and part inwards to the nares ; but the main 

 body of the muscle has a median plane and covers the entire frontal superficies of the 

 nares and upper lip. Below the nasal orifices, towards the median Hue, the fibres pass 

 inwards curvilinearly, and are dovetailed with those of the levator labii superioris pro- 

 prius, and partially inserted into the intermaxillary bones. They likewise cross above 

 the nares and decussate with those of the opposite side of the face. 



Concerning this muscle's action, the attachments and direction of its fibres sliow that 

 it is an elevator, retractor, and dilater of the nares. 



Mandibular Arch and Side of Skull = Infracranial— The muscles clothing the 

 symphysial portion of the mandible greatly increase the remarkable appearance and 

 unusual form of the bone of this region. Of these the levator labii inferioris is 

 ' Memoir cited, p. 59. 



