ORDER ISOPODA — N^SA. 45 



GENUS N^SA. Leach. ^< 



Body ovate-oblong, with many of the characters of the preceding. Last segment of the tail 

 largest, and furnished on each side with a simple pedunculated appendix ; penultimate joint 

 of the thorax larger than the last. Nails bifid. 



NjESA ovalis. 



JV<Esa ovalis. Say, Jour. Acad. Nat. Sciences, Vol. 1, p. 484. 



Description. Body oval, depressed. Caudal segments three ; the last half as long as the 

 body, triangular, obtusely rounded at the tip, with three longitudinal raised hnes at the base, 

 of which the middle one is most conspicuous. Lateral processes dilated, depressed, recti- 

 linear within, and rounded on the external margin. Head somewhat unequal. Eyes con- 

 spicuous, hemispherical. Antenna equal. Labrum triangular, advanced, very conspicuous, 

 and forming with the base of the superior antennas a rounded termination. Feet all armed 

 with bifid nails, none of which close on the preceding joint. 



Length, O-lo. 



According to Mr. Say, this species, which I have not seen, is common in the bays and 

 inlets of the United States, creeping on seaweed and other marine plants. It occurs as far 

 south as Florida. 



{EXTRA-LIMITAL.) 



N. caudaia. (Id. lb. p. 482.) Body oblong-oval, semicylindrical. Last segment of the tail tubercu- 

 lated, as long as the four preceding ones united, with a deep sinus at the tip, within which are two 

 to four teeth, and a larger vertical one above its base. First caudal segment conspicuous. Color, 

 fuscous. Length, 0-25. Egg harbor, N.J, 



N. depressa. (Id. lb. p. 483.) Body broad, depressed, punctured, linear. Hands of the anterior 

 feet dilated, ovate, monodactyle; thumb as loag as the palm. Second pair with cyli dric hands, 

 with an incurved thumb; the others ciliated. First caudal segment concealed. Length, 0-5; 

 breadth, 0-2. Hab. with the preceding. 



