458 CETACEA. 



portions are separated in the middle line by an intercalated little cartilage, or it may- 

 be described as beginning at the right border of the trachea by two free ends or 

 pieces which enclose a cartilage at the middle and unite at the left wall of the tube. 

 The first piece on the dorsal surface begins at the right margin of the tube by two 

 free ends, lying side by side, and which unite about the middle of the tube, the 

 single end just bending sufficiently round the left margin of the tube to form its 

 wall. On the ventral surface, the first cartilage has two distinct cartilages behind it. 

 The first is a small free cartilage opposed to its right third and terminating on the 

 right wall of the tube, but not entering into the formation of the dorsal wall. The 

 second lies against the two remaining thirds, but the cartilage passes right round 

 the left margin to their dorsal surface, and running obKquely backwards to the right 

 to the beginning of the first bronchus of that side. At its origin on the ventral surface, 

 it has a short portion bent back before itself, but this piece does not reach to the 

 left border of the tube (PI. XXVIII, fig. 10). The first cartilage of the dorsal surface 

 has two behind it, overlapping each other in the middle line, but confined to its own 

 side of the trachea. The second cartilage of the ventral surface has two cartilages 

 behind it similarly arranged with regard to each other. The third dorsal cartilage 

 begins by a pointed end on the left wall of the tube, but soon divides into two halves, 

 which lie parallel and are confined to the dorsal wall. The fourth ventral cartilage 

 enters partially into the formation of the dorsal wall. Commencing at the right 

 side of the tube, it can be traced describing four spiral lines, but never encircling the 

 trachea, being almost exclusively confined to the ventral wall. It receives a process 

 from the right of its commencement, and gives off two at the end of its first coil, 

 which pass on to a portion of the dorsal surface, the anterior lying behind the dorsal 

 prolongation of the second ventral cartilage ; the posterior being prolonged beyond 

 it to the angle of divergence of the first bronchus and trachea. The rest of the 

 wall at the origin of the right bronchus is made up by small cartilaginous plates, 

 and a similar arrangement holds good at the point where the last bronchus is given 

 off; the ventral plates being generally bifurcated structures, only having a very 

 limited dorsal surface and sometimes enclosing small plates between them. On the 

 bronchi and their divisions, the cartilages are arranged in spiral rings, and on the 

 larger bronchi I have counted as many as five distinct coils in one cartilage. The 

 coils, however, are not simple, for secondary ones are given off, which are embraced 

 in the primary ones as much shorter coils. 



Lungs. — The pulmonary organs of Tlatanista as shown in Plate XXIX, 

 fig. 1, are there thrown apart, the better to expose the heart and its surroundings. 

 Each lung in the adult is 19-50 inches in length. When examined in the fresh con- 

 dition, its substance, as in others of the Whale tribe, is particularly spongy and 

 of a firmish texture. Both lungs are nearly similar in outline, and while they may 

 be described as single, or without marked division into lobes, the upper segment in 

 each is nevertheless marked by a shallow cleft, so as to warrant division into an 

 anterior and posterior lobe. The former, especially the left lung, has a well-marked 

 semilunar marginal excision, which produces a rounded lobular promontory quite 



