AMPHIBIA. 533 



the interstices of walls, or other similar retreats, in the spring 

 emerging from their state of rest and seeking the water in order 

 to deposit their eggs, in the form of strings of jelly three or four 

 feet long, with a double row of black dots, when their loud croak 

 may be heard at a considerable distance. They are two or three 

 weeks later than the Frogs in depositing their eggs, after which 

 process they return to the land. In August, the tadpoles, having 

 completed their transformation, leave their native element for the 

 land, dispersing themselves in all directions. 



Of the genus Bufo, about twenty species are enumerated ; 

 several are found in the United States, but only one is seen in 

 the northern parts of the Union. These have simple toes and a 

 distinct tympanum. 



The COMMON AMERICAN TOAD, B. Americanus, (B. vulgaris, 

 Storer,) is about three inches in length. It is furnished with a 

 sac for holding the water which it obtains through the skin. The 

 skin, shed at certain intervals, is, according to Mr. Bell, swal- 

 lowed as soon as it is detached. 



The NATTER JACK, or RUNNING TOAD, B. calamila, is a spe- 

 cies of toad of a yellowish brown color, with a bright yellow line 

 running down the middle of the back. It never leaps, nor does 

 it crawl with the usual toad-pace, but its motions are more like 

 running. This species is found in Ireland. 



The BAHIA TOAD, Phryniscus nigricans, is a species noticed 

 by Mr. Darwin, at Bahia Blanca. He graphically says of it, 

 "If we imagine, first, that it had been steeped in the blackest 

 ink, and then, when dry, allowed to crawl over a board freshly 

 painted with the brighest vermilion, so as to color the soles of its 

 feet and parts of its stomach, a good idea of its appearance will 

 be gained." Instead of being nocturnal, like other toads, it 

 crawls about during the heat of the day, over dry sand-hillocks 

 and arid plains. 



The MITRED TOAD, B. margaritifer, (Lat. pearl-bearing,) re- 

 ceives its name from the peculiar conformation of the head. It is 

 an American species. 



The SURINAM TOAD, (see Chart,) Pipa Surinamensis or mon- 

 strosa, is from six to eight inches in length, and four to five in 

 breadth. It has a large and triangular head, is without teeth or a 

 tongue ; its tympanum is concealed beneath the skin ; its eyes are 

 small and placed near the margin of the upper jaw. The skin 

 is of dirty brown color, thickly studded with reddish tubercles. 

 The general uncouthness of its appearance is increased by a 

 phenomenon almost unexampled in the animal kingdom. The 

 female has the back pitted with a great number of small cells, 



