MIMICRY IN THE COMMON SOLE. 239 



On a Possible Case of Miraiciy in the Common Sole. 

 Bj A. T. Masterman, M.A., D.Sc, F.L.S. 



[Read 5th March, 1908.] 



There are two common species o£ Weaver (Trachinidse) found in British 

 waters, namely, the Greater Weever (TracJmiics draco) and the Lesser 

 Weever {Tracliiniis vipera). Both are venomous, and the poison is concen- 

 trated at the spines of the first dorsal fin and the opercular spine in its 

 immediate neighbourhood. 



The habits of T. vipera are the better known. On all occasions it attempts 

 to bury itself in the sand until only the top of its head, with eyes and mouth, 

 and dorsal fins are above the surface. In this position it apparently lies in 

 wait for the shrimps and small fry which form its food. As a probable 

 adaptation to this habit, the eyes and mouth of the fish are elevated into a 

 dorsal position, so that the least possible surface of the body need be exposed 

 above the sand. 



The habits of T. draco are closely similar. It is abundant off the coast of 

 Norway, and on occasions it is taken in great shoals. Of its habits Professor 

 Smitt remarks * : — 



" The Great Weever lives in water of a moderate depth with a sandy 

 bottom. It buries itself in the sand and keeps in hiding, in order more 

 suddenly to attack its prey, which consists of small fishes and crustaceans." 



In British waters J. draco is found further off-shore and in deeper water 

 than T. vipera. The experience of our trawlers in the Southern North Sea 

 and in the English Channel is that 1. draco is found in greatest abundance 

 on the off-shore trawling-grounds, whilst T. vipera occurs most frequently 

 close inshore in sandy bays. T. draco " occurs along the whole west coast 

 (of Norway) from Bergen in Norway to the south of Scania, and into the 

 Baltic as far as the coast of Prussia, where it is, however, extremely rare.''' 

 " To the south it is common as far as the Mediterranean and the Black Sea.'^f 

 T. vipera is very abundant in the English Channel and the North Sea, but 

 Smitt describes only a single specimen from the coast of Norway. In British 

 waters, especially towards the north, it is more common than T. draco. Like 

 the latter, it is often found in large shoals. 



In both species the first dorsal fin has six (occasionally seven in T. draco, 

 according to Kroyer |, who remarks that seven spines are common in the 

 males) sharp strong spines or rays, with a conspicuous black membrane. Upon 

 provocation this fin is erected and spread out in the most conspicuous manner. 

 Its intense black colour, in contrast with the pale yellow and brown tints of 



* ' Scandinavian Fishes,' Part i. p. 131. t Loc. cit. p. 130. 



J C/". Canestrini, ^ Fauna d' Italia.' 

 LINN. JOURN. — ZOOLOGY, VOL. XXX. 19 



