THE CATFISH. 177 



bony pectoral arch, and to the foremost interneurals, in 

 such a manner as to give a very firm, bony support to the 

 three defensive spines. 



The joints at the bases of these spines, though not 

 characteristic of fishes in general, but a peculiarity of a 

 small group, show an interesting kind of animal mech- 

 anism, and are well worthy of an examination. 



Examine first the attachments of the dorsal spine. It 

 is fastened by a ring to the top of the third interneural. 

 The first interneural is small, the second and third inter- 

 neurals are grown together solidly into one piece (the 

 buckler), and the notched tip of the backward process 

 from the skull (the helmet) fits against the anterior 

 edge of this piece. The dorsal spine arises from the 

 third interneural, and a rudiment of another spine from 

 the top of the second interneural. This rudiment is a 

 small, oval bone, forked below. It is set against the base 

 of the great spine in front, and acts as a sort of bolt, or 

 fulcrum of support. The widened neural spines also con- 

 tribute to the support of the great spine, as can be readily 

 seen. 



Examine one of the pectoral spines. Study the beauti- 

 ful joint by which it is united to the pectoral arch. In 

 how many directions is it movable ? 



Observe the great strength and solidity of this pectoral 

 arch, and the comparative weakness and small size of the 

 pelvic arch. 



The catfish is a representative of the class Pisces, or fishes 

 of the great branch Vertebrata (or back-boned animals). 



Other Fishes of very different structure can readily 

 be obtained for study in any locality. 1 A common 

 sucker, or a buffalo fish, is recommended for study, and 



1 Use Jordan's Manual of the Vertebrates for identifying the species of 

 fishes. 



NEED. ZOOL. 12 



