EPARTERIAL BRONCHIAL SYSTEM. 141 



This arrangement is exceptional, as the *' bilateral eparterial 

 type" is usually symmetrical. It leads, however, directly up 

 to the condition presented by the two following forms, Cebus 

 nigcr and PJioca. 



The cardiac bronchus is well developed, derived from the 

 right stem-bronchus between A" and B' . 



The artery passes to the cardiac bronchus from the ventral 

 aspect of the main pulmonary artery, before the same has 

 crossed to the lateral aspect of the stem-bronchus, resembling 

 the arterial arrangement noted in AitcJienia, although a secon- 

 dary branch (6^'^) is seen, in the dorsal view, winding around 

 the stem-bronchus in the usual situation of the main artery of 

 the Azygos lobe (PL XXIII). 



VIII. Cebus niger — Capuchin Monkey. 



Corrosion preparation of the bronchial system and pulmon- 

 ary artery. Columbia University Museum, No. 484. PL 

 XXIV, Dorsal view. PL XXV, Ventral view. 



This type appears as the direct result of further development 

 cephalad of the preceding form. 



The cephalic trunks. A, of both sides appear as " eparterial 

 bronchi," each dividing into the characteristic secondary 

 branches A' and A" . On the right side the trunk A has shifted 

 a little further cephalad, nearer to the tracheal bifurcation, than 

 on the left side. 



The main caudal branches and the cardiac bronchus are 

 arranged as in the preceding form. 



IX. Phoca vitulina — Harbor Seal. 



Corrosion of bronchial system and pulmonary artery. Colum- 

 bia University Museum, No. 584. PL XXVI, Ventral view. 



This final type presents the complete " bilateral eparterial 

 system," perfectly symmetrical ; each cephalic trunk {^A^ is 

 situated on the stem-bronchus close to the tracheal bifurcation, 

 cephalad of the main pulmonary artery, and divides sym- 



