THE FLOUNDER FAMILY. 327 



as a prominent swelling beyond the line of the body. As aids 

 in diagnosing the mutilated young flounders of this stage are 

 the proportionally smaller eyes than in the young round fishes, 

 the structure of the tail, and the depression of the snout 

 between the eyes. 



The most prominent feature in the succeeding stage is the 

 thrusting upward of the terminal caudal " whip " by the de- 

 velopment beneath it of certain cartilaginous elements (hypural), 

 and of the true fin-rays. The ventral margin is also finely dotted 

 on each side with black pigment. The hypural cartilages so 

 largely increase that they form a deep vertical boundary to the 

 tail, the terminal (notochordal) process being bent upwards, and 

 appearing, when viewed externally, as a slight filament. The 

 depth of the body at the base of the tail has greatly increased. 

 The left eye now shows a tendency to move forward and upward 

 and a slight twisting of the frontal region is discernible, so that 

 the symmetry of the head is no longer perfect. Small lateral 

 bands indicate the ventral fins. 



The examples referable to the long-rough dab were captured 

 in the mid-water net at the end of August, and ranged from 

 5 to about 13 mm. Similar specimens, however, are likewise 

 procured both in July and in September. Their distance from 

 the inshore waters, and the depth at which they were found afford 

 grounds for connecting them with this species, yet though the 

 general outline is similar the mouth resembles that of the dab. 

 At 11 mm. in length, the eyes are still lateral (Plate XII, 

 fig. 12), and various black chromatophores occur along the 

 lateral median line at the edge of the muscle-plates, on the 

 head and on the jaws. Moreover, as Holt 1 pointed out, lines 

 of black pigment follow the muscle-plates of the post-anal 

 region ventral to the notochord. The most advanced of the 

 series measured 13 or 14 mm. When one of 13 mm. was placed 

 on its side a small part of the left eye was visible above the 

 margin of the head (Plate XII, fig. 13) ; moreover, it was slightly 

 anterior to the right eye, and its axis was directed somewhat 

 forward. On the right side, four black pigment-spots were 

 situated at the base of the interspinous bones, and the same 



1 Op. cit. p. (JO. 



