PETROMYZON. 423 



stomach and intestines have longitudinal valves on the inside passing 

 through their whole length, but nothing similar to a pylorus. There 

 is no pancreas, and, of course, no caeca. 



The liver is one lobe ; is rather small for the size of the animal, but 

 large for the size or length, of gut. There is no gall-bladder, and 

 where the ducts enter the gut I do not know. The heart is at the 

 lower part of the chest, composed of an auricle and a ventricle, enclosed 

 in a pericardium which is cartilaginous. The trunk of the branchial 

 artery, which is one as it passes up, sends off the seven pairs of bran- 

 chial branches. 



They have seven inspiratory holes, crossing from the oeosophagus, 

 viz. one to each branchia, which enter the cavity of each at the union 

 of the edges. They have seven expiratory passages leading out at the 

 opposite edge, and open externally separately from each other. The 

 branchiae are placed in the chest of the animal, which is of some length, 

 and not in the setting on of the head to the trunk, as in most other 

 fishes. The chest is composed of ribs which are cartilaginous \ There 

 are fourteen branchiae in the whole, viz. seven on each side, which are 

 in pairs : each gill is composed of two parts opposing each other, making 

 a flattened cavity between them, each side of which is composed of 

 longitudinal folds, the edges of which are loose in the cavity' 2 . Each 

 branchia is enclosed in a distinct capsula or pleura. 



The air-bag or < swimmer ' passes along the back as low as the 



? and opens into the oesophagus near the mouth ; at this 

 opening, and for some way down, it is valvular, or has a number of 

 ridges in it, as if for the increase of surface, similar to the branchiae 3 . 



The kidneys are long, small, thin bodies, passing from the anus 

 upwards, one on each side, running in the same direction, almost con- 

 tiguous to each other : their length is somewhat more than the half of 

 the lower part of the abdomen : they are attached by one edge to the 

 back, where they receive their vessels, somewhat similar to the kidneys 

 in snakes ; and on the other, or loose edge, passes the ureter, which is 

 large in this fish, it having no bladder. The ureters become smaller 

 when near to their openings, which are into one cavity, just above and 

 close to the anus ; which cavity is common to them and the openings 

 of the belly [peritoneal canals] for the exit of the ova. This common 



1 [They are analogous to ribs ; see ' Hunterian Lectures,' ' Vertebrate Animals,' 

 8vo, 1846, p. 52. fig. 11.] 



2 [Hunt. Preps. Phys. Series, Nos. 1024—1030.] 



3 [This is the median branchial canal, beneath the oesophagus, terminating in a 

 blind end behind, and communicating anteriorly with the oesophagus near the mouth 

 by a double valvular orifice.] 



