362 MANUAL OF ZOOLOGY. 



fishes (e. g., PtericMhys, Coccosteus, &c.), caused by the fact that 

 the head is protected with an exoskeleton of dermal bones. 



SUB-ORDER B. ANACANTHINI. This sub-order is distin- 

 guished by the fact that the fins are entirely supported by 

 " soft " rays, and never possess " spiny" rays ; whilst the ven- 

 tral fins are either wanting, or, if present, are placed under the 

 throat, beneath or in advance of the pectorals, and supported 

 by the pectoral arch. The swim-bladder may be wanting, but 

 when present it does not communicate with the oesophagus by 

 a duct. 



As in the preceding order, the Anacanthini are divided into 

 two groups, distinguished by the presence or absence of the 

 ventral fins. In the first of these groups (Apoda) are only a 

 few fishes, of which one of the most familiar examples is the 

 little Sand-eel (Ammodytes lancea), which occurs on all our 

 coasts. In the second group (Sub-brachiata) in which ventral 

 fins exist, are the two important families of the Gadida and 

 Pleuronectidce. The Gadidcz or Cod family, comprising the 

 Haddock, Whiting, Ling, and Cod itself, is of great value to 

 man, most of its members being largely consumed as food. In 

 the Pleuroncctida or Flat-fishes are comprised the Sole, Plaice, 

 Turbot, Halibut, Brill and others, in all of which there is a 

 very curious modification in the form of the body. The body, 

 namely, in all the Flat-fishes (fig. 136) is very much compressed 



Fig. 136. Pleuronectidse. Rhombus punctate. Natural size (after Gosse). 



from side to side, and is bordered by long dorsal and anal fins. 

 The bones of the head are twisted in such a manner that the 

 two eyes are both brought to one side of the body. The fish 

 usually keeps this side uppermost and is dark-coloured on this 

 aspect, whilst the opposite side, on which it rests, is white. 

 From this habit of the Flat-fishes of resting upon one flat sur- 



