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 Perennibranchiates. 
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, Nectwrus (formerly 
Menobranchus) Jateralis 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 Zriton are laid singly on sub- 
merged leaves; those of Diemyctylus viridescens are laid 
* See Gage’s Observations on, . . Necturus. Buffalo, 1882. 
