502 



Survey of Fishing -Grounds, West Coast of Ireland, 1890—1891. 



The state of the specimens was such that we were only able to count the scales 

 of the straight part of the lateral line in five examples, all small. The number varied 

 from 38 to 40, being 38 in two, 39 in one, 39 or 40 in one, and 40 in one. In 

 two specimens the total number of rows of scales between the head and the caudal 

 fin could be ascertained. In one it is 48, in the other 50. Thus the small Ply- 

 mouth examples agree with the Norwegian specimen Q, and with the large Irish 

 female C, but have a considerably less number of rows than the Irish A. lophotes 

 males A and B. 



It appeared probable that information of value might be gained by counting 

 the vertebrse, which we accordingly exposed in several specimens, with the 

 following results: — 



It is apparent that, if we have counted correctly, all the small examples have 39 

 vertebrse, and all the larger ones, whether male or female, either 41 or 42 vertebrae. 

 Since the number of vertebrse is known to roughly correspond in Pleuronectids to 

 the number of the fin-rays, it seems probable that the small examples have actually 

 a less number of fin-rays than the large ones, so that the difficulty is not to be 

 explained away as due to an error in counting the rays. We are not aware of any 

 observations showing that the number of either rays or vertebrse increase with age, 

 and do not regard this as probable. A variation of two or three in the number of 

 the vertebrae in a species is by no means remarkable, but it is remarkable that we 

 should have found such a constant variation in relation to the size of the individual. 

 The variation is confined to the caudal region, the number of abdominal vertebrse 

 being nine in both large and small examples. 



Taking all our information into consideration it appears to us that the evidence 

 of the identity of A. laterna and A. lophotes is sufficient to outweigh the difficulty 



