268 Linncean Society, 



gated air-bladder, with the usual vascular and cellular structure of 

 the lungs of a reptile. 



The branchice consist of elongated, sub-compressed, soft, pendu- 

 lous filaments, attached to cartilaginous branchial arches ; these 

 arches are not joined together, or to the os hyoides by an interme- 

 diate chain of cartilages or bones below, nor are they articulated to 

 the cranium above. There are six branchial arches on each side, 

 and five intervals for the passage of the water from the mouth to the 

 branchial sac. All the branchial arches do not support branchial 

 filaments ; but only the first, fourth, fifth, and sixth. The first and 

 last branchial arches each support a single row, the fourth and fifth 

 each a double row of branchial filaments. ITie second and third 

 branchial arches have their full proportions, but offer not the slight- 

 est trace of gills. The branchial sac is pretty large, and opens ex- 

 ternally by a small vertical fissure immediately anterior to the ru- 

 dimental pectoral extremities. 



The heart is situate below the oesophagus, in a strong pericardium ; 

 it consists of a single auricle and ventricle and a contorted bulbus 

 arteriosus, with a longitudinal valvular process as in the Siren. The 

 two branchial arteries, which wind round the gill-less arches, after- 

 wards unite together on each side, and give off branches which form 

 the pulmonary arteries, or those which go to the air-bladders. 



The apparatus for aerial respiration commences by a short, single, 

 wide and membranous trachea, or ductus pneumaticus, which com- 

 mences by a longitudinal laryngeal slit, one line in extent, situated 

 three lines behind the orifice of the pharynx : a single plate of car- 

 tilage is continued from this laryngeal opening forwards to that of 

 the pharynx : the plate is as broad as the floor of the pharynx, and 

 its office seems to be to prevent the collapse of the parietes of that 

 tube, and to keep a free passage for the air to the trachea. This tube 

 dilates at its lower end into a sac with very thin parietes, which com- 

 municates directly witli each division or lobe of the air-bladder. 

 ITiese lobes or lungs are partially subdivided into small lobes at their 

 anterior and broadest part ; and then continue simple and flattened, 

 gradually diminishing to an obtuse point situated behind the poste- 

 rior extremity of the cloaca. The whole of the parietes of the lungs 

 is honey-combed : the cells are largest, deepest and most vascular 

 and subdivided at the anterior and broader end of the lung. The 

 lungs are situated behind the ovaria, the Iddneys, and the perito- 

 neum, which is in contact with merely that part of their ventral 

 Jtiattened surfaces, not covered by other viscera. 



The two kidneys are quite distinct, very long and narrow, but 



