OP ARTS AND SCIENCES. 23 



Fig. 5. Slightly older than the preceding stage. The eye, from the right side, 

 projects ahove the line of the snout; the coloring much as in 

 fig. 4. The anal, dorsal, and caudal fins are, however, more 

 advanced. 



PLATE VIII. 



Rhombus maculatus Mitch. 



Fig. 1. Young sinistral Flounder, natural size, showing the color assumed when 

 the fish is placed upon a dark mud-colored ground. 



„ 2. The same fish, somewhat enlarged, showing the coloring assumed 

 when placed upon a yellowish sandy soil. 



„ 3. Another specimen of the same species, somewhat younger than the 

 preceding stages, showing the coloring assumed when placed upon 

 a mottled ground (partly gravel, partly sand) somewhat darker than 

 the yellowish sandy soil. 



„ 4. Black pigment spots forming the blotches along the lines of the rays 

 of the dorsal, when fully expanded. 



„ 5. Another portion of the dorsal, showing the spots when contracted. 



„ 6. A portion of the pigment spots of the colored side, showing the red, 

 the yellow, and the black pigment spots when fully expanded, the 

 darker tints between the colored pigments representing the masses 

 of iridocytes. 



PLATE IX. 



PSEUDORHOMBUS OBLONGUS STEIN. 



Platessa quadrocellata Storer PI. XXXI. fig. 3. 



Fig. 1. Egg of Flounder, showing the symmetrical head of embryo. 

 „ 2. Head of young Flounder, the fourth day after hatching. Seen from 



above. 

 „ 3. Head of fig. 4. Seen from below. 

 „ 4. Young Flounder. Seen in profile. Quite transparent. Remarkable for 



the great development of the dorsal embryonic fin, 6.5 mm in length. 

 „ 5. Somewhat older than fig. 3. First trace of heterocercal tail. 

 „ 6. Older than fig. 4. The anterior part of the dorsal is developed before 



the rest, forming a sort of anterior dorsal. The eyes are still 



symmetrical. 

 „ 7. Young Flounder, quite well advanced. The fins are all differentiated. 



The right eye has, however, moved, thus far, but little forward and 



upward. 



PLATE X. 



Plagusia Sp. 



Fig. 1. Young Plagusia, slightly over an inch long. Seen in profile. The eyes 

 of the two sides are equally distant from the snout : they are placed 

 symmetrically with reference to a longitudinal axis, and a plane 



