TELEOSTEI. 317 



the fossil spines known as " ichthyodorulites." The structure 

 in question consists of the first ray of the pectoral fins, which 

 is largely developed and constitutes a formidable spine, which 

 the animal can erect and depress at pleasure. Unlike the old 

 " ichthyodorulites," however, the spines of the Siluridce 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 cer- 

 tain of the extinct Ganoid fishes (e.g., Pterichthys, Coccosteus, 

 &c.), caused by the fact that the head is protected with an exo- 

 skeleton of dermal bones. The Siluroid fishes, however, are 

 hardly represented at all in the fossil state, being only known 

 by two or three doubtful Tertiary examples: 



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. 



The only important families in this sub-order are the Gadida 

 (Cod-family) and the PletironectidcB (Flat Fishes). The Gadidce 



Fig. 280. Rhombus miniums. A small fossil Turbot from the Eocene Tertiary of 



Monte Bolca. 



comprise the living Cod, Haddock, Whiting, &c., and appear 

 to date their existence from the Eocene Tertiary. The Pleuro- 

 nectidtz comprise the living Sole, Flounder, Plaice, and the 

 like, in which the body is very much compressed from side to 



