AND PHYSIOLOGY. 



101 



as representatives are the 

 Shad and Flounder, and of 

 the latter, the Shark and 

 Sturgeon. 



219. Two Kinds of Ver- 

 tebra. — The only kinds of 

 Vertebrae in Pishes are the 

 Dorsal and Caudal. These 

 vary in number from seven- 

 teen to more than a hundred. 

 Their bodies (vertebrae) pre- 

 sent on both articulating sur- 

 faces a conical depression which 

 is filled with a soft matter 

 having the same use as the 

 elastic intervertebral sub- 

 stance in the human vertebral 

 column. 



220. No Sternum or Pel- 

 vis. — The Sternum and Pel- 

 vis are both wanting in fishes, 

 and the anterior and posterior 

 extremities are rudimentary, 

 being represented by fins. 



Fig. 113, 



Fig. 112, 



Skeleton of the Perch. 





















'•••: .-•••/ /W 



Section of the bony scale of Zepidosteus. a. Showing the regular distribution of the 

 Lacunae and of the connecting Canalicali. K Small portion more highly magnified. 



219. What are the only Vertebrae of Fishes ? What is peculiar about their articula- 

 ting surfaces ? 220. Why have Fishes no Sternum or Pelvb ? 



