128 



ORDERS OF FISHES. 



ctenoid scales. The ventral fins are generally beneath or in 

 advance of the pectorals, and the duct of the swim-bladder 

 is invariably obliterated. 



Fig. 41»ti.— iiViOHi/iH.s miniiniig. A small fossil Tnilint from the Eocene Tertiaiy of 

 Monte Bolca. 



The chief living families of this sub-order are the Perch 

 family {Pcrcidm), the Mullets {Mugilidm), the Mackerel 

 family (Scomheridce), the Gurnards (Sclerogenidce), the Blen- 

 nies (Blenniidce), the Gobies {Gohiidce), and the Chsetodons 

 {Chcctodontidce). The fossil representatives of this sub-order 

 are mainly Tertiary; but the genus Beryx (fig. 497) dates 



Fig. 407. — Tjo-i/.c Lcvesicnsis. A Percoirt fisli from the Chalk. 



from the Cretaceous period. The Cretaceous Syllcemus is 

 also probably an ancient representative of the Mullets. In 

 the Eocene Tertiary of Monte Bolca occur several remark- 



