MADE AT THE PLYMOUTH LABORATORY. 249 
the rectangular form anteriorly. The scales are short from before 
backwards and broad transversely ; the exposed portion is short, 
and projects outwards from the skin at an angle with the embedded 
portion ; at the edge is a single row of spines, of which the central 
one is considerably the longest. These spines are not of the same 
length in all the scales, but longer ones occur at scattered points 
over the skin. 
Only two other kinds of flat fishes are known in which what may 
be called subcaudal finlets are present; or, to put the same fact in 
other words, the fishes in which this character is present are sepa- 
rated by other differences into three species. The other two are 
Zeugopterus unimaculatus, Steenstrup, and Zeugopterus norvegicus 
(Giinther). The former is distinguished by the fact that the first 
ray of the dorsal fin is produced into an elongated filament, while 
in the latter this character is wanting, and the pelvic fins are 
separate from the ventral, not united with it as in punctatus. The 
other specific characters consist i minor differences in the generic 
characters themselves. ‘The perforation of the branchial septum 
exists also in Arnoglossus megastoma, commonly called the megrim 
at Plymouth; and in consequence of this Steenstrup included this 
species with the three previously mentioned in the genus Zeugo- 
pterus. But as this last species does not possess the subcaudal 
prolongations of the dorsal and ventral fins, nor the other characters 
which unite the first three, it is best to confine the name Zeugo- 
pterus to these three species. 
The three species of Zeugopterus, then, have what may be described 
as a continuous distribution. No two of them are geographically 
separated, and they have not been found anywhere beyond a limited 
region on the coast of HKurope. All three occur on the British 
coasts. Punctatus is, as has been stated, frequently taken in 
Plymouth Sound ; it occurs all along the south coast of England, and 
also on the east coast. It has been taken on the east coast of Scot- 
land as far north as the Orkneys, on the west coast of Scotland in 
the Firth of Clyde, and on the east coast of Ireland. Northward 
the species extends to the north coast of Norway, southward to 
the northern shores of France, but it is absent from the Mediter- 
ranean. Norvegicus is likewise a northern form, not ranging to the 
Mediterranean. I have taken several specimens at Plymouth: one 
specimen was taken during the survey of fishing grounds on the 
west coast of Ireland, 1891—2 ; three specimens have been taken in 
the Clyde. It is somewhat rare on the Scandinavian coasts. Uni- 
maculatus, on the other hand, is a Mediterranean form, occasionally 
but rarely taken on British and northern coasts. I have never 
obtained a specimen at Plymouth. On the south-west coast of Scot- 
