348 Prof. Owen's Description of the Lepidosiren annectens. 



by cellular tissue to all the surrounding parts, and particularly to the ribs, of 

 which they bear the impressions on their posterior surface. The anterior part 

 of each lung- is divided into four or five small lobes, of which the first is about 

 half an inch long, of a triangular form, with the apex forming the most ante- 

 rior part of the lung : the other lobes decrease in size, and at the distance of 

 one inch and a half from the anterior end, the lung takes on the form of a simple 

 compressed bag, and so continues to its posterior extremity. The parietes of 

 the lung present a moderate thickness throughout, and the whole of the inter- 

 nal surface is cellular, the cells having the same proportional size and form as 

 in the respiratory part of the lung of a serpent. The ceils are largest and most 

 subdivided at the anterior fourth part of the lung ; the livid colour of which in 

 the specimen dissected by me attested the great natural vascularity of the part. 



The pulmonary artery*, formed by the union of the branches from the se- 

 cond and third branchial arteries, descends between the vena cavaf in front 

 and the left branch of the vena pulmonalis;}: behind, to the interspace of the 

 lungs ; here it distributes branches to the anterior lobes, and then divides : 

 each division § extends along the mesial side of its corresponding lung to the 

 extremity. The blood distributed by the capillaries of this artery over the cells 

 of the lung is collected into a vein|| which returns along the lateral or outer 

 margin of the lung as far as the commencement of the lobulated part ; here 

 it crosses obliquely the anterior surface of the lung, and unites with its fellow 

 at the beginning of the interspace of the lungs : the common pulmonary vein 

 runs parallel with and behind the vena cava for a few lines ; then obliquely 

 pierces the pericardium and enters the sinus formed by the expansion of the 

 vena cava, and continues attached to the parietes of that sinus till it reaches 

 the auriculo-ventricular aperture, where it terminates, close behind the singular 

 cartilaginous knob before- mentioned. 



Renal System. 



The kidneys^ are narrow bodies, three inches in length, and about two lines 

 in diameter at their widest part, which is near the cloaca ; from this extremity 

 they gradually contract, as they pass forwards, to a fine point. They are 



* Tab. XXVI. fig. 2, /. t lb. e. * lb./. § lb. m. || lb. n, n. 



f Tab. XXVII. fig. 7, h, h. 



