478 ZOOLOGY. 



observed at the Yukon River in lat. 60 N., but the climate 

 there is milder than that of Labrador. The common toad 

 and a salamander (Plethodon glutinosa Baird ?) extend to 

 Southern Labrador. 



Nearly 700 species of existing Batrachians are known, 101 

 of which are North American, and about 100 fossil forms 

 have been described. 



There are five orders of Batrachians, Professor Cope's 

 classification being adopted in this work. Those Batrachians 

 with persistent gills are sometimes called Perennibrancliiates. 



Order 1. Trachystomata. The sirens have a long eel-like 

 body, with persistent gills ; there is no pelvis or hind limbs, 

 and the weak, small fore legs are four or three-toed. The 

 great siren, Siren lacertina Linn., is sometimes a metre in 

 length, and has four toes in the fore leg ; it lives in swamps 

 and bayous from North Carolina and Southern Illinois to 

 the Gulf of Mexico. A small siren with three toes and 

 small gills is Pseudobranchus striatus Le Conte. It occurs 

 in Georgia. 



Order 2. Proteida. This group is represented by the 

 Proteus of Austrian caves and the mud-puppy (Necturus) 

 of the United States. These Batrachians have bushy gills, 

 with gill-openings and well-developed teeth. In Proteus, 

 which is blind, there are three toes in the fore feet and two 

 in the hinder pair. In the mud-puppy, Necturus (formerly 

 Menobranchus) lateralis Baird, each foot is four-toed. The 

 head and body are broad and flat, brown with darker spots. 

 It has small eyes and is about half a metre (from 8 inches to 

 2 feet) in length. It inhabits the Mississippi Valley, extend- 

 ing eastward into the lakes of Central New York. The 

 Proteus as well as the mud-puppy lay eggs. 



Order 3. Urodela. The tailed Batrachians or Salaman- 

 ders rarely have persistent gills, these organs being larval or 

 transitory ; the body is still long and fish-like, the tail some- 

 times with a caudal fin-like expansion as in the newts, but is 

 usually rounded, and the four legs are always present. With 

 only one or two viviparous exceptions, most of them lay eggs 

 in the water. The eggs of Triton are laid singly on sub- 

 merged leaves ; those of Notophthalmus viridescens are laid 



