SIREN. 393 



will obstruct the water passing in from without. The circular cartilages, 

 which are above the opening, above and between which the two arteries 

 pass, are lined on the inside by the membrane of the fauces, which is 

 not very thin. 



The lungs are small tubes passing nearly through the whole length 

 of the abdomen, behind and on the inside of the abdominal viscera. 

 Their upper ends are behind the heart, the lower are within three inches 

 of the anus ; here they become small and end in a point. They are 

 attached through their whole length by a thin membrane to the root of 

 the mesentery, to the aorta descendens, and, on the right at the lower 

 end, to the inferior vena cava. The whole of their inner surface is 

 honeycombed ; their substance is amazingly vascular, receiving many 

 arteries from the pulmo-branchial trunk. A vessel passes down all 

 along the anterior edge of the lungs, where the [mesentery?] is 

 attached. 



The vein corresponding to the artery is just such another vessel, and 

 is continued from the lower end of the lung to the upper as one pretty 

 uniform canal, collecting the small branches in its way, and at length 

 opening into the vena cava a little below the termination of that vein 

 in the heart 1 . 



The Siren [Siren lacertina, Linn.]. 



This animal is the nearest of this tribe to the fish ; therefore, at 

 present 2 , is the first remove, or link in the chain, above the fish. 



This animal, in shape, is very much like the freshwater eel: the 

 largest that I have seen is about 15 inches long. It is of a dark colour 

 on the back, but rather lighter on the belly. Its head is broad from 

 side to side, but flatter from the upper surface to the lower : the 

 eyes are very small, situated near the anterior part of the head, only a 

 little way behind the nose ; therefore I should suppose their extent of 

 locomotion is not great. On the lateral and posterior parts of the head 

 are the external openings of the gills, and, immediately behind them, are 

 the two legs or arms. From thence the body of the animal is continued 

 back to the anus without much alteration of shape : it then becomes 

 smaller, and flattens on the sides, forming a superior and inferior edge, 

 which edge is a kind of superadded structure, answering the purpose of 

 a fin, and becoming sharper and narrower to the end of the tail. 



The two legs or arms come out from the shoulders : they are composed 

 of arm, forearm, hand, and four fingers ; each finger is made up of three 



1 [Hunt. Prep. Phys. Series, No. 915.] 



2 [Had Hunter known the Lepidosiren and its anatomy, he would, most probably, 

 have recognized it as an intervening link between the siren and the fish.] 



