232 BRITISH FRESHWATER FISHES 



The Grey Mullets {Mugilidcu) belong to the 

 group of Mugiloids, which differs from the Fercoids 

 in a single character — the insertion of the pelvic fins 

 well behind the base of the pectorals so that the 

 pelvic bones are not attached to the clavicles ; 

 whether they are on this account to be regarded as 

 more primitive or more specialized than the Fercoids 

 is not quite certain. 



The Sand-smelts (^Athcrinidce) are closely related 

 to the Grey Mullets, but the two other families of 

 this group are very different, the Barracudas 

 {Sphyrcenidce) being large carnivorous Fike-like 

 fishes, almost the most dangerous inhabitants of 

 the tropical seas, whilst the Thread-fins {Polynemidce) 

 are peculiar in that the lower pectoral rays are 

 detached from the rest of the fin and are produced 

 into long filamentous feelers. 



Numerous species of Grey Mullet are known from 

 temperate and tropical seas, frequenting bays and 

 estuaries and often entering fresh water. Our British 

 species are three in number ; in all the body is 

 moderately elongate, slightly compressed, the head 

 short and broad, the mouth small, terminal, pro- 

 tractile, bordered above by the pra^maxillaries only ; 

 the setiform teeth are so feeble that they appear 

 merely as a fringe on the jaws ; the eyes are lateral, 

 placed high, but more visible from below than from 

 above. The head is scaly and the scales on the 

 body are large, numbering forty to fifty in a 

 longitudinal, and about fourteen in a transverse, 

 series ; there is no lateral line. The first dorsal fin 

 is formed of four pungent spines, the second of a 

 spine and eight or nine soft rays ; the anal originates 

 somewhat in advance of the dorsal and has three 



