DE. J. MUEIE ON THE FOEM AND STEUCTUEE OF THE MANATEE. 179 



continuously spiral, as obtains in Halicore, but, as Stannius figures in Manatus, there 

 are some which bifurcate and obliquely cross the long axis of the tube. In my female 

 specimen the trachea, f of an inch in diameter, split at about 5 inches distance from the 

 lungs, and each bronchus entered almost at the summit of the pulmonary organ. Within 

 the lung it goes in a straight line to the posterior extremity, lying a little to the inner 

 side of the middle. About a dozen bronchia branch outwards, these again subdividing 

 in the pulmonary substance. 



There is a narrow and moderate-sized thyroid gland on each side of the upper portion 

 of the trachea. 



The lungs, their shape and singular relation to the diaphragm, &c. have often been 

 commented on since Daubenton's original description. My illustrations of the parts in 

 their natural position, figs. 20 and 37, supplant verbal detail. Some two or three inden- 

 tations, 1^ to 1 inch deep, are the only trace of segmentation ; but anteriorly they ter- 

 minate in a short rounded lobule (/, fig. 41). In the uninfiated state the greatest thick- 

 ness of the lung-substance of the female was 1 inch; extreme length 23 inches; 

 breadth towards the anterior extremity 2f inches, about the middle 8^ inches, and 

 rearwards 1^ inch, tapering finally to an obtuse termination sunk in a pocket at the 

 lumbo-vertebral end of the diaphragm. 



2. Hyoid and the surrounding pharyngo-glossal Jleshy parts. 



The hyoidean arch comprises three bony pieces — to wit, a small, flat, oval basihyal, 

 and a pair of long subcompressed stylohyals. Each of the latter measured 1-7 in the 

 young male, and 2*2 inches in the older female. To the upper narrow extremity of 

 the stylohyal a strip of cartilage an inch long is fixed, by which it is fastened to the 

 inferior tubercle of the exoccipital. Betwixt the other (broader) end of the bone and 

 the basihyal is a >-piece of cartilage representative of ceratohyal. This extends con- 

 tinuously along the outer border of the basihyal, and forms a retrocurrent wing to it on 

 either side ; and to these the anterior cornua of the thyroid alse are attached. The 

 thyrohyals or connecting ligaments between the hyoid and larynx are tough thickish 

 membranes, and apparently contain a considerable amount of yellow elastic tissue. 



I examined the intrinsic muscles of the larynx carefully, and found that, notwith- 

 standing the rudimentary nature of the epiglottis and comparative absence of laryngeal 

 pouch, I could differentiate superior and inferior aryteno-epiglottidei, and even noted 

 fibres equivalent to a thyro-epiglottideus. Indeed, each and all of the laryngeal muscles 

 are relatively well developed. The extrinsic laryngeal muscles maintain a fair size, 

 with attachments of the ordinary kind. The keratic muscles, so notably developed in 

 Cetacea, are feebly represented in Manatus ; and the hyoepiglottidei of the former are 

 entii'ely wanting in the latter, as might have been expected from the condition of the 

 epiglottis. 



The sterno-hyoid and sterno-thyroid are interblended. An omo-hyoid was not indis- 



