1 64 AMPHLBIA 



Fam. Sirenid.^:. — The members of this family have three 

 pairs of fringed, external gills, retained throughout life. A 

 long and slender body, hind limbs wanting, fore limbs short, 

 with three or four fingers. Maxillary bones absent ; small 

 teeth on the vomers, jaws without teeth, and covered with 

 horny sheaths. Eyes small, without lids. 



There are only two species, both found in the south-eastern 

 States of North America. In the "mud-eel" {Siren lacertind) 

 there are three gill-clefts, the first of the original four being 

 closed. (Plate XIV., C.) The animal reaches a length of two 

 and a half feet ; the tail, about one-third of the total length, is 

 compressed and furnished with a fin-membrane. The early de- 

 velopment is unknown but it has been shown that in young 

 specimens the gills are small and functionless so that they are 

 redeveloped in the adult. In Pseudobranchus striatus there is 

 only one pair of gill-clefts and the gills are covered by the skin, 

 and functionless. There are only three fingers and the length 

 of the adult is not more than seven inches. 



Fam. Proteid.e. — The few species placed in this family 

 resemble the Sirenidae in all respects except in the absence of the 

 hind legs and of teeth in the jaws ; in the Proteidae teeth are 

 present in both the upper and the lower jaw and both pairs of 

 limbs are present. The eyes are without lids. Three pairs of 

 external gills persist throughout life, but there are only two gill- 

 clefts on each side, the first and last being closed up. 



Proteus anguinus, known in German as the Olm, is a blind 

 and colourless species living in the underground waters of the 

 caves of Dalmatia. (Plate XIV., A.) The limbs are small and 

 slender with three fingers on the fore- foot and two on the hind. 

 The tail is compressed and provided with a fin-membrane. The 

 eyes are rudimentary and concealed beneath the skin. The total 

 length is less than one foot. Necturus maculatus, which has also 

 been named Menobranchus lateralis, is similar to Proteus and of 

 about the same size, but it is pigmented and the eyes are func- 

 tional ; it has four toes on each foot. It lives in North America 

 to the east of the Mississippi and in the Canadian lakes. 

 Typhlomolge rathbuni is a subterranean form like Proteus, white 

 and blind ; it has four toes on the fore-foot, five on the hind. 

 This animal is only three inches in length and has a deep fold 

 of skin on the throat formed of the united opercular flaps. 



