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 whieh 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 cells 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 cavat 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 d 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 caya, 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 
* Tas. XXVI. fig. 2, J. T Ib. e. Ib. $ Ib. m. 
i Ib. u, 5. 
€ Tas. XXVII. fig. 7, A, h. 
