202 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



numerous; pectorals transparent; ventrals mottled brown like the body; dorsal 

 darker to 2d spine; caudal crossed at base by a curved bar, foreshadowed by a 

 dorsal and ventral dark spot. 



At a length of 40 mm. the first 2 dorsal spines are flexible, about twice the 

 height of the pungent 3d, from which the others are graduated upward. The 

 membrane is deeply emarginate before the 3d spine. The lobe of the fin so set off 

 is darker than the rest of the fin and has a small spot darker still above and 

 behind the base of the 1st support. 



I have had specimens up to 70 mm. in length in which the first 2 supports re- 

 mained higher than the others. Fish of such size swim often in sidling tilted 

 poses, with anterior lobe up and caudal spread wide. Several swimming among 

 Thalassia were nearly uniform olive or yellow-green, and banded green. Others 

 were marked with gray and maroon, repeating faithfully the colors of the frayed 

 Zonaria among which they moved. When pressed closely these small fish hide 

 by plunging head foremost into sand like their elders. 



With a proper series available it is plain, as Parr has shown, that as they grow 

 the anterior lobe of the dorsal stands up relatively less and less conspicuously 

 above the remainder of the fin, until it is merged almost indistinguishably with 

 it. At the same time the color pattern becomes more elaborate and the color of 

 the body richer in hue. Sexual dimorphism in color and structure makes its 

 appearance in specimens of larger size. 



Where sand and grass meet to the west of Southwest Key, a diver may find 

 the young with their upstanding dorsal lobes, the adolescent showing the ap- 

 proach of sexual maturity in their dimorphism, and the fully mature all together. 

 The same range of growth stages may be found also on sandy bottom to the 

 north of Loggerhead Key, where the largest individuals occurred most com- 

 monly. 



In a living male of 130 mm. the body was bluish gray, or in some lights green 

 or greenish gray; scales on side bordered with faint olive about bluish centers; 

 side of head between snout and opercular margin with seven brassy lines nar- 

 rower than the bluish interspaces, the one below eye forked ventrally; dorsal fin 

 very narrowly blue-margined, colored like the body anteriorly at base, more and 

 more widely rosy posteriorly, the color spreading inward from the blue border, 

 the rosy ground marbled with about twenty irregular blue streaks; anal essen- 

 tially the same, except that blue rather than rose is dominant; pectorals rosy 

 toward tip; ventrals bluish; basal four-fifths of caudal irregularly parted in four 

 olivaceous bnnds by wavering lines of blue, the terminal fifth rosy with a pale 

 ;ind narrow blue margin; iris carmine. 



The third 1 scale down and back from the tenth in lateral line in the male has 



1 In the type of Xyrichthys splendent Castelnau (a male 146 mm. long), a corresponding 

 spot falls on the second scale below and behind the eleventh in lateral line, as it does in 1 of 

 2 specimens in the U. S. National Museum (no. 43293). This too is a male, 141 mm. long, 

 with a minor spot on the next scale lower in the eleventh on the one side and the second 

 lower in the eleventh on the other. Five others in Vienna, and all of 6 from Bahia, have a 

 black spot in the second row below lateral line. This difference, with the faded color patterns 

 of preserved material, will serve to distinguish the two species. Of the Brazilian form I have 

 found no authentic record in the West Indies or Caribbean. 



