482 TELEOSTEI [CH. 



as it is usually termed, the anal) median fins are stiffened by bony 

 dermal fin-rays, their extreme tips alone are supported by horny 

 rays or ceratotrichia. The dermal rays have been shown by 

 Goodrich to be nothing more than series of thin dermal bones 

 covering both sides of the skin flap which constitutes the fins. 

 When a longitudinal series of them are fused together they form a 

 " spiny " or " hard " fin-ray ; when this does not take place they 

 give rise to a jointed or "soft" fin-ray. The dermal fin-rays are 



FIG. 237. The right half of the pectoral girdle and right pectoral fin of a Cod, 

 Gadus morrhua, x ^. 



1, 2. Supraclavicle. 3. Cleithrum. 4. Coracoid (Hypocoracoid). 



5. Scapula (Hypercoracoid). 6. Postcleithrum. 7. Ossified 



radialia of the fin. 8. Dermal fin-rays. 



termed by Goodrich "lepidotrichia." The paired fins are as a 

 rule much less developed than in Chondrichthyes. They are stiffened 

 by lepidotrichia and ceratotrichia just like the unpaired fins, and 

 the pectoral fin is supported by three or four baseosts embedded in 

 its base which correspond to the cartilaginous basalia in the pectoral 

 fins of Chondrichthyes. Baseosts are often absent from the pelvic fin, 

 the dermal rays of which articulate directly with the pelvic girdle. 

 The pectoral girdle is a degenerate structure, it consists of two 

 small plates of cartilage which are very far separated from one 



