486 MANUAL OF ZOOLOGY. 



species of Salmon and Trout. Also belonging to this group are the Sheat- 

 fishes (Siluridcz), which are chiefly noticeable because they are amongst the 

 small number of living fishes possessed of structures of the same nature as 

 the fossil spines known as "ichthyodorulites." The structure in question 

 consists of the first ray of the pectoral fins, which is largely developed, and 



Fig. 262 Electric Eel (Gymuotus electricus). 



constitutes a formidable spine, which the animal can erect and depress at 

 pleasure. Unlike the old "ichthyodorulites," however, the spines of the 

 Sihtridce have their bases modified for articulation with another bone, and 

 they are not simply hollow and implanted in the flesh. The " Siluroids " 

 are also remarkable for their resemblance to certain of the extinct Ganoid 

 fishes (e.g., Pterichthys, Coccosteus, &c.), caused by the fact that the head is 

 protected with an exoskeleton of dermal bones. The largest European 

 species is the Silurus glanis of the Swiss lakes, and of various European 

 rivers. Another remarkable member of this family is the Malapterurus of 

 the Nile and West Coast of Africa, which is endowed with electrical powers. 



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 Gadidcz and 

 Pleuronectida. 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 Pleuronectidcz or Flat-fishes are comprised the Sole, Plaice, 



