474 AUTCHILL ON THE FISHES OF NEW-YORK. 



He is found only during the warm season ; and often disappears fey 

 the beginning of September. 



Sometimes when he is distended to hardness with air, and thrown into 

 the water, he floats away to some distance, his white belly resembling a 

 mass of froth : when he suddenly discharges the air, sinks, and escapes. 

 3. Mathematical Tetrodon. (Tetrodon mathemalicus.) With olive 

 green smooth back, satin-white sides, snow-white belly, and ecliptical 

 lateral line. 



The grand specimen of this curious fish, which I examined on the 

 29th June, 1814, had the folio winsr characters : 



Length twenty-two inches ; depth five and a half; breadth three and 

 a half. 



Skin without scales, and on the back and sides smooth. The belly 

 planted with short and acute prickles in quincunx rows. 



Colour of the back a dark olive or deep bottle green ; of the sides a 

 splendid silky argentine nearly three inches broad, with a delicate cast 

 of green ; of the belly a snowy white. All these divisions well defined, 

 without stripes, bands, or spots. 



Eyes pale yellow, and surrounded by an irregular line at the distance 

 of an inch and more. 



Lateral line departing from the ring encompassing the eye, like a tan- 

 genf"5 ascending in a superb curve toward the back ; sweeping boldly 

 down from the olive of the back through the satin of the side ; and then 

 running direct to the tail ; putting one in mind of the ecliptic cutting 

 the equator. 



A transverse line from one lateral to the other, above the pectoral 

 (ins. Another line from the eye-circle to the transverse line, and parallel 

 to the lateral line, making a sort of parallelogram. 



Lips skinny, thick, and loose, resembling almost the human lips. 



One dorsal and one anal fin, both, far back 



