series in my sample, except for darkening and the 

 appearance of pigment at the distal edge of the 

 caudal peduncle, in the branchial chambers, and 

 around the urohyal (figs. 5 and 6). 



MIGRATION OF THE EYE 



Specimens of 7 mm. SL are symmetrical; the 

 right eye has not begun to migrate (fig. 5). The 

 dorsal fin continues its development anteriorly, 

 and its origin is over the anterior edge of the eye. 

 The supraorbital bars on the cranium have not 

 begun to become modified. 



By about 8 mm. SL the right eye has moved 

 only slightly ; the origin of the dorsal is above and 

 posterior to the ethmoid region of the cranium and 

 the origin of the fin base remains unattached. Tis- 

 sue between the ventral edge of the anterior por- 

 tion of the dorsal fin and the frontal region of the 

 cranium is becoming thin, and the supraorbital 

 bars have begun to shift onto the ocular sides as 

 an accompanying depression begins to form above 

 the left eye. 



By 10.5 mm. SL the right eye has migrated 

 dorsoanteriorly but its upper edge is not yet level 

 with the supraorbital bars ; the origin of the dorsal 

 is attached to the ethmoid region of the cranium 

 and its point of attachment has shifted onto the 

 right side of the head, over the nostrils. The right 

 side is the blind side in the adult. The area of thin 

 tissue between the dorsal fin and the supraorbital 

 bars is wider. The supraorbital bars continue their 

 shift to the left side, and the depression of the 

 cranium above the left eye is larger. 



On a 14 mm. SL specimen the upper edge of 

 the right side eye is visible through the thin tissue 

 below the dorsal fin (fig. 7). The shifting of the 

 supraorbital bars has created a large depression 

 over the left eye. The origin of the dorsal fin re- 

 mains attached. The right eye has not yet begim 

 to move through the head onto the left side. In 

 larger specimens the eye will move through the 

 head in the area between the dorsal fin and the 

 depression created by the shift of the supraorbital 

 bars. 



SEQUENCE OF OSSIFICATION 



I cleared and stained several specimens to de- 

 termine the sequence of ossification. The degree of 

 ossification can be assessed by the intensity of the 

 stain (alizarin red S) absorbed by the bone. In 



this discussion I consider any bone that absorbed 

 stain to be ossified. 



On a 1.7 nun. SL specimen only the cleithrum, 

 the distal edges of the preopercle and preopercular 

 spines, and the sphenotic spine and its base showed 

 any ossification. 



By 3 mm. SL some ossification is seen in the 

 cranial cap, lower jaw, premaxillary, and the four 

 elongate dorsal fin rays. By 3.5 mm. SL the three 

 elongate pelvic fin rays, the maxillary, four bran- 

 chiostegal rays, and six elongate dorsal fin rays are 

 ossified. The palatine and parasphenoid are stained 

 and extend from the symphysis of the upper jaw 

 to the cleithrum ; these bones will form part of the 

 floor of the neurocranium. At this size all stained 

 areas are in the head and pelvic fin region. Six 

 canine teeth are present in the lower and four in 

 the upper jaw, but none are stained. A slight 

 thickening on the ventral edge of the posterior 

 part of the notochord is the rudimentary hypural, 

 and it is only slightly ossified, if at all. 



Ossification is still restricted to the head and 

 pelvic fin base region at 4.1 mm. SL. All seven 

 branchiostegal rays, the urohyal, and the preoper- 

 cle and opercle in the opercular series are now 

 ossified. The vertebrae and neural and haemal 

 spines have not begim to ossify. Ossification at 4.9 

 mm. SL is essentially similar to that of the 4.1 mm. 

 SL specimen; again the anterior neural and hae- 

 mal spines are visible but are not stained. They are 

 not attached to the vertebrae and appear as thin 

 lines between the vertebrae and the dorsal and 

 anal fin rays. 



At 5.5 mm. SL the right pelvic fin base, three or 

 four caudal fin rays (but not the hypural ele- 

 ments), the dorsal aspect of the subopercle, and 

 some vertebrae and associated neural and haemal 

 spines have begun to ossify. The 16 anterior neural 

 spines and the anterior seven haemal spines, and 

 the dorsal rim and sides of the neural arch on the 

 second, third, and fourth vertebrae are lightly 

 stained. The first vertebra and its neural spine 

 are not stained. The occipital region of the neuro- 

 cranium and the scapula have begun to ossify. 



The areas of ossification, as determined by ab- 

 .sorption of alizarin red S stain, are larger and the 

 color is more intense at 6.4 mm. SL than on smaller 

 specimens. At this size the notochord is upturned 

 and two hypural elements are differentiated. Ten 

 caudal fin rays are stained, and five are associated 



LARVAL BOTHID FLATFISH AND SPOTFIN FLOUNDER 



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