128 U.S. NATIONAL MUSEUM BULLETIN 2 02 Vol. 3 



Color in alcohol. — Ground color of head and body greyish green, 

 back darker than sides and belly; 5 or 6 narrow lengthwise reddish lines 

 present on sides, broken and irregular anteriorly, clearest on caudal 

 peduncle; skin of belly wrinkled and with short reddish lines in the 

 grooves; posterior part of caudal peduncle with a broad encircling 

 band of dark purple, color not intense enough to obscure lengthwise 

 lines; rays of fins yellowish, membranes pale; caudal membranes 

 hyaline. 



Remarks. — This specimen has round open nostrils with slightly 

 raised rim, small scattered dermal spines, a conical snout, and fin ray 

 count characteristic of Canthigaster. Specimens of Arothron immacu- 

 latus of 10 and 22 mm. have the nasal tentacles well formed and forked, 

 snout blunt, and head and body with thickly set, long dermal spines. 



The coloration is different from that of our smallest specimens of C. 

 solandri, janthinopterus, or rivulatus. The National Museum collec- 

 tion has no specimens small enough for comparison, only of solandri 

 and these do not have the lengthwise reddish lines mentioned in the 

 description above. 



Family TETRAODONTIDAE 



By Loren p. Woods and Leonard P. Schultz 



Genus AROTHRON Miiller 



Arothron Muller, Abh. Akad Wiss. Berlin, p. 252, 1839 (type species, Arothron 

 testudinarius Muller {—Tetrodon stellatus Bloch and Schneider)). 



KEY TO SPECIES OF AROTHRON FROM THE MARSHALL ISLANDS 



la. Head, back, and sides with white spots. 



2a. Body brown, belly scarcely, if any, lighter than back; head and body 

 everywhere with small close-set white dots smaller than pupil, those 

 of back usually smallest; basal two-thirds of pectoral, dorsal, and 

 anal fins dark brown, usually spotted, distal third pale; caudal fin 

 brown with small white spots almost to distal margin; lips dark with 

 crowded small white spots A. meleagris (Lacepede) 



26. Back light grayish brown with darker brown blotches; belly pale whitish; 

 back with large round white spots, almost as large as pupil, spots 

 smaller on caudal peduncle and caudal fin, larger and elongate on 

 lower sides; belly with many narrow lengthwise dark lines, broader 

 near sides, particularly well defined below pectoral fin; gill opening 

 and pectoral fin base sometimes encircled by 3 to 5 alternating light 



and dark rings; lips pale A. hispidus (Linnaeus) 



1&. Head, back, and sides without white spots, either plain brown or with few 

 to very numerous black spots on a lighter background coloration. 



3a. Coloration plain light brown to dark grayish brown on back, sides, and 

 belly with dark lengthwise parallel lines; outer caudal fin rays always 

 black; dark ring around mouth not complete, median part of chin 

 pale; nasal tentacles dusky, lighter than ground color of back; dorsal 

 and anal fins pale or slightly dusky. 



A. immaculatus (Bloch and Schneider) 



