306 



LOWER VERTEBRATES. 



oped in these species. Tlie iV'i maculatus is an nbumlant animal in tlie great lakes 

 and the Oliio and its tributaries. It is a good swimmer and is rather handsomely 

 spotted. (Fig. 174). 



Order VI. — TRACHYSTOMATA. 



In the Traehystomata the bones of the skull are less numerous than in any of the 

 tailed orders, since the maxillary and palatine arches are entirely absent. There is but 

 one family, the Sirenid^. These are eel-like animals with one pair of legs (the ante- 

 rior) and without teeth, except a rasp-like patch on the roof of the mouth. This fam- 

 ily contains two genera. Siren and Pseudobranchus. Both of them have the gills 

 persistent, but in the latter genus they become functionless with age, owing to the 



thickening of their fibrilla;. Both have four toes on the feet. The Siren lacertina is 

 found in ditches in the swamps of the southern states of North America from South 

 Carolina to the Rio Grande of Texas, and up the Mississippi as high as Alton, Illinois. 

 It reaches a length of twenty-four inches and is of a dark lead color. The Pseudo- 

 branchus striatus is broadly striped with yellow, and does not exceed ten inches in 

 length. It is not rare in Georgia and Florida. 



Some years ago I had occasion to observe a Siren confined in an aquarium, which 

 had been taken near Alton, 111. (Lat. 39°). I first saw it in midwinter ; it was then 

 without gills, but frequently came to the surface and took mouthfuls of air, parts of 

 which would escape through the slits on the neck. Tliere were frequently convul- 

 sive movements of the latter region, by which the anterior, and sometimes the poste- 

 rior slits were opened. Water was at the same time drawn in through the external 



