AND THEIR DISTRIBUTION AT DIFFERENT AGES. 113 



Motella in tlie second of tlie stages above mentioned, is described 

 and figured in my paper in this Journal, vol. i, p. 47. 



Caranx tracJmrus — the Scad, or Horse-mackerel. 



This is a pelagic species frequently taken in mackerel nets. Its 

 young are also pelagic, and I have taken them in the tow-net in 

 August and September. In August, 1888, one 5*4 cm. (2'1 inches) 

 was taken three or four miles off Loae. On September 8th this 

 year I took two, 2*4 and 3"5 cm. long, to the south-west of the 

 Mev/stone ; and on September 12th, one 2*5 cm. long, about five 

 miles south of the Mewstone. 



Comparisons and Conclusions. 



1. Flat fishes. — If we consider first the species of the genus 

 Pleuronectes alone we find some curious and interesting differences. 

 We find that the flounder and plaice when immature, that is under 

 7 and 9 inches respectively in length, and less than two years old, 

 are almost entirely absent beyond the 20 fathom line. The young 

 of these two species are abundant in the estuaries of Cattewater 

 and the Hamoaze. In June, 1889, I found plaice 1 to 3 inches 

 long, spawned the previous spring, in abundance in Whitsand Bay, 

 which is not an inlet, but a bay open to the sea ; but during the pre- 

 sent summer, I have trawled there several times in July and 

 September and found no young plaice at all. On the other hand, 

 the dab {PI. limanda) , even under one inch in length and only three 

 months old, occurs, though not abundantly, near the 30 fathom line, 

 a little inside the Eddystone. It is much more abundant at this 

 age in Cawsand and Whitsand Bays, at depths of 3 to 7 fathoms. 

 Up to 5 inches in length it is common in the Cattewater, where 

 also larger specimens are not uncommon. The trawlers working off 

 Plymouth between 20 and 40 fathoms bring up numbers of small 

 flat fishes, but, with very few exceptions, these are all dabs or scald- 

 backs, Arnoglossus laterna. The smallest dabs I have obtained from 

 the trawlers were 4i inches long, a length which may be reached 

 by some individuals at one year of age. Thus, although specimens 

 of less size and age than this are not uncommon at depths of 10 to 

 30 or 40 fathoms, the great beam trawl does not catch them because 

 its meshes are too large. I have not kept records of the small 

 scald-backs brought up by the great beam trawl, though when study- 

 ing other subjects on board trawlers I have seen numbers of them 

 brought up. During the present summer, however, when fishing 



