81 



caudal portion of the spine, it is directed downwards, and often 

 forms, with its fellow of the opposite side, a ring, from the lower 

 part of which arises a long spinous process, similar to that which 

 is situate on the dorsal face of the vertebra. 



11. The ribs are sometimes wanting; at other times, they 

 encircle the whole abdomen, and, in a small number "of fishes, 

 they are fixed to a series of unpaired or single bones, which 

 should be regarded as the sternum. They frequently sustain 

 one or two stylets which have an outward direction, and pene- 

 trate the flesh. Sometimes there are similar stylets arising from 

 the bodies of the vertebrae, and hence it is that, in certain genera, 

 such as herrings, fish-bones become so numerous. 



12. On the middle line of the body, we also find a certain 

 number of bones, called inter&piwil, (Fig. 43, /. ) which gene- 

 rally rest upon the ends of the spinous processes of the vertebrae, 

 and, by their opposite ex- _,,. 



tremities, artieulate with the 



rays of the middle fins, (//.) 



These rays are sometimes 



pointed bones, called stinys, 



or spines ; sometimes they 



are stalks or stems bony 



only at the base, formed of 



a multitude of small articu- 



lations in continuation, and HTTERSPINAL BONES. 



often branched towards the end. These last appendages are 



called soft, or articulated rays : they always form the caudal 



fin, and sometimes there are no others. 



13. The lateral fins, which represent the extremities, are 

 terminated by rays similar to those of the vertical fins, and 

 analogous to fingers. At the base of the pectoral fin we find a 

 series of from four to five small flat bones, comparable to the 

 bones of the carpus, which, in their turn, are attached to two 

 flat bones which seem to be the radius and ulna enlarged. This 

 apparatus is supported on a species of bony belt, situate' imme- 

 diately behind the gills, and on which the operculum applies : it 

 consists of a series of three bones, extending from the cranium 

 to the hyoid apparatus, and supports posteriorly a long stylet. 

 The principal piece that enters into its composition is that which 

 supports the fore-arm, which may be compared to the humerus, 

 (See Fig. 42, Page 80.) : it joins below with that of the opposite 



11. What are the characters of the ribs ? 



12. What are the interspinal bones ? What arc the riys of the fins ? 



13. What parts of fishes represent the extremities of mammals ? 



