NOTES AND MEMORANDA. 619 



whilst Holt* obtained them in April and May on the west coast 

 of Ireland ; whilst young specimens about 42 mm., obtained on the 

 19th August, he considers to be four to six months old. The spawning 

 season therefore does not aid to the identification of the present 

 specimens, nor does the place where they were captured. Both 

 species occur in the Moray Firth, the halibut being, if anything, 

 the commoner. 



The eggs of the halibut are very large, and vary, according to 

 different observers, between 3-0 and 4-0 mm. From their large size 

 we should expect the larvae issuing from them to be also large. On 

 the other hand, the eggs of the pole-dab are comparatively small — 

 1-15 to 1-70 mm., and the length of the vitelligerous larva only 4-0 to 

 4-6 mm. The latest stage of the larval form of the latter species, 

 described by Holt, was 5-57 mm. ; the yolk was absorbed, but the 

 notochord and the marginal fins are still in the embryonic condition 

 {loc. cit., Plate IX., Fig. 75). There is a blank between this stage 

 and the next at 42 mm., when the adult characteristics have already 

 been assumed. On the other hand, only one reputed specimen of a 

 post-larval halibut has up to the present been described, and that 

 by Dr. Petersen.^ This specimen was 32 mm. long ; the migration 

 of the left eye had hardly begun, and the fin-rays were absent from 

 the pectorals and ventrals. The fin-ray formulae of the unpaired fins 

 left doubts as to whether the specimen was a young halibut or pole- 

 dab, but the large mouth and depression above the snout led Petersen 

 to class it as the former. 



The two specimens taken in the Moray Firth were obtained in 

 the bottom tow-net, in company with post-larval plaice, lemon-dabs, 

 and one topknot. Their lengths (in spirit) are 12 and 14 mm. ; 

 metamorphosis has hardly begun; the notochord is bent upwards, 

 though not into its final position. True fin-rays to the number of 

 eighteen have appeared in the caudal fin, but in the marginal fins no 

 true rays could be detected until the specimens had been cleared in 

 xylol and mounted in balsam. The length and narrowness of the 

 caudal region show a very early stage of metamorphosis. Across 

 the abdomen the breadth is 2 mm. ; across the caudal region, im- 

 mediately behind the abdomen, only 1 mm., omitting the fins. The 

 head is 18 per cent, of the extreme length and the mandible is 50 

 per cent., the eye 25 per cent, of the length of the head. Black 

 pigment is present in the form of stellate chromatophores ; any other 

 colour which may have been present has disappeared in the spirit. 



* Trans. Boy. Soc. Duhlin, vol. v. (Series II.), j). 84. 



t "On the Biology of our Fiat-Fishes," Danish Biol. Stat., iv., 1893, p. 130, Plate II., 

 Fig. 20. The same specimen was mentioned by Collet and Lilljeborg. 



