74 Linneean Society. 



branchial sac. All the branchial arches do not support branchial 

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



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 with each division or lobe of the air-bladder. 

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

 broadest towards the cloaca : the ureters communicate with the back 

 part of the common termination of the oviducts. 



The ovaria are two long, flattened bodies, with ovisacs and ova of 

 different sizes : many between 2 and 3 lines in diameter, scattered 

 among clusters of other ova of smaller size. The oviducts are distinct 

 tortuous tubes, which commence by a very wide and thin-coated 

 portion, opening by a slit, 3 lines wide at their anterior extremity, 

 and not communicating with each other before opening into the pe- 

 ritoneal cavity, as in the Plagiostomes. 



A small Allantois is situated between the oviduct and rectum. 

 The cloaca receives the above parts in the following order, — first, or 

 most anteriorly, the common opening of the peritoneal canals ; se- 

 condly, the anus ; thirdly, the Allantoid bladder ; fourthly, the ovi- 

 ducts, with the ureters, which open into the back part of the oviducts. 



The brain consists of two elongated subcompressed distinct cere- 

 bral hemispheres ; a single elliptical oj^tic lobe, or representative of 

 the bigeminal bodies ; a simple transverse cerebellar fold, not cover- 

 ing the widely- open fourth ventricle ; largely developed pineal and 

 pituitary glands ; and a single corpus mammiliare. 



The nerves given off from the brain, were the olfactory ; the optic, 

 which arose from the same point at the middle line between the 

 crura cerebri, and did not decussate ; the fifth pair ; the acoustic ; the 

 ])neumogastric ; and lingual nerves : there were no traces of the third, 

 fourth, or sixth nerves ; there being no muscles to the eyeballs. 



The eyes are very small, and adhere to the skin, which passes over 



