184 U.S. NATIONAL MUSEUM BULLETIN 202 Vol. 2 



maxillary covered by preorbital; premaxillary protractile; jaws equal 

 in length or nearly so; gill membranes joined to side of isthmus but 

 mth a narrow free fold across it; head naked, except a few scales in a 

 patch on upper part of opercle usually present; body scaled; all fins 

 naked, except caudal fin scaled basally; lateral line complete; usually 

 branched pectoral ray second from dorsal edge longest; dorsal rays 

 VIII,12 to 14 almost always VIII,13; anal 111,10-13 almost always 

 111,11; pectoral rays ii,12 to 15; pores in lateral line 19 or 20+1 

 (rarely 2) +5 or 6 to base of caudal fin rays; 3 or 4 scales above 

 lateral line to base of spiny dorsal and 9 or 10 scales below it to anus; 

 pelvics 1,5; branched caudal rays 6+6; nostrils small, anterior one 

 tubular, posterior nasal opening covered by a dermal flap arising from 

 its anterior edge; interorbital space convex; teeth short on sides, 

 uniserial, about 9 to 14 on each side in both jaws, usually tips curved 

 a little posteriorly; middle pair of enlarged teeth on lower jaw fitting 

 between the middle pair at tip of upper jaw when mouth is closed, 

 these teeth obliquely slanting, not projecting straight forward; both 

 lips plicate, this condition usually continuing on chin. 



Figure 100. — Sketch showing the shape of the dark color bar in the pectoral fin of five 

 species of Thalassoma: a, T. duperry (Quoy and Gaimard); h, T. lucasanum (Gill); c, T. 

 lunare (Linnaeus); d, T. lutescens (Lay and Bennett); e, T. amblycephalus (Bleeker). 



KEY TO SPECIES OF THALASSOMA FROM THE MARSHALL AND SOUTHERN MARIANAS 



ISLANDS 



la. Color pattern consisting of about 6 or 7 blackish, wedge-shaped, vertical bars 

 interspaces whitish; radiating from eye about 5 broad dusky bars (red 

 when alive) alternating with pale ones (olive when aUve) of about same 

 width; dorsal fin with a blackish median streak. 



T. hardwickei (Bennett) 



16. Color pattern not as in la. 



2o. Operculum crossed with 3 or 4 narrow curved streaks or whitish lines often 



obscure in preserved specimens, head dark brown, body lighter brown; 



chin without plicate folds; 2 dark bars across pale chin; centers of 



