438 SCHULTE, SEI WHALE. 



is continuous with the cricoid cartilage, between the ventral bars of which the sac communicates 

 with the larynx. Caudad the membrane diminishes in width terminating by a pointed extrem- 

 ity at the level of the origin of the right apical bronchus. From the end of the membrane a 

 shallow groove, convex to the right, is continued to the angle of the bifurcation. Along this 

 groove the ends of the tracheal cartilages are in contact but not fused, so that in this foetus there 

 are no complete rings. The number of those intervening between the membrane and the bifur- 

 cation is only three; of those with ends widely separated by the membrane, five. This condi- 

 tion of incomplete rings throughout agrees with Dubois' statement for Mystacoceti in general. 

 On the other hand in B. antipodum (Beauregard and Boulart ') there are only three rings which 

 are not closed ventrally and in B. musculus Miiller finds that out of seven or eight rings 

 only five are incomplete. As regards B. rostrata (= acuto-rostrata) Carte and MacAlisterV' 

 statement is incomplete, but their description I take as meaning that at least one complete 

 ring is present. Turner 3 describes in B. sibaldii three "somewhat irregularly formed carti- 

 laginous hoops immediately above the bifurcation." In the illustration of his plate viii, fig. 37, 

 the ventral ends appear in contact but not fused. On the left side there are five free tips abut- 

 ting on the membrane, on the right six, one being a small bit of cartilage opposite the tracheal 

 bronchus. In the same species Beauregard and Boulart describe five open rings. The first 

 and second are connected to the right of the median line, and similarly the third and fourth 

 to the left. 



Bronchi. Only their extra-pulmonary portions are here considered. The tracheal, or right 

 apical bronchus, is given off just caudad of the apex of the lung and immediately enters its 

 substance, the lung filling the angle between it and the right stem-bronchus so completely, that 

 only along its lateral aspect can it be said to be extra-pulmonary, and here it is lodged in a deep 

 groove in the lung. Its diameter is 3 mm. The bifurcation is concealed by the arch of the 

 aorta. The stem-bronchi diverge slowly and are in contact by their mesal walls as far as 

 the level of the right pulmonary artery. The right then curves strongly dextrad and enters the 

 lung under cover of the artery, having the pulmonary veins below it at the turn, though the 

 upper vein soon passes to its ventral surface. The left primary bronchus takes a longer and 

 more oblique course to the hilum, passing dorsal to the right pulmonary artery. At its entrance 

 the left artery is rostral to it as is also the left upper vein, the remaining two pulmonary veins 

 on this side are caudal to it. The right primary bronchus measures 4.5 mm. in diameter, the 

 left 4 mm. 



THE THORAX. 

 (Plates XLIX, Figs. 2 and 3, L.} 



The thorax is broad and deep, approaching the keeled form ventrally, the dorsoventral 

 diameter apparently exceeding the transverse, though in consequence of the distortion of its 

 right side but little reliance can be placed upon its proportions. The rostral closure of the 

 cavity, inside the arch of the first rib, is largely effected by the great rectus-scalene muscle- 

 complex, between the diverging arms of which the dome of the pleura is embraced, there being 



1 Beauregard and Boulart. Jour, de 1'Anat. et de la Phys., T. 18, p. 623. 



2 Carte and MacAlister, op. cit., p. 243. 



3 Turner, W., op. at., p. 236. 



