GEOGRAPHICAL DISTRIBUTION OF ANIMALS 447 



V 



est ray of light,. or else it is undeveloped, as if the fish had 

 abandoned the effort to see. In many cases luminous spots 

 or lanterns are developed by which the fish may see to 

 guide his way in the sea, 

 and in some forms these 

 shining appendages are 

 highly developed. In one 

 form (^Ethoprora) a lumi- 

 nous body covers the end 

 of the nose, like the head- 

 light of an engine. In an- 

 other (Ipnops) the two eyes 

 themselves are flattened 

 out, covering the whole top 

 of the head, and are lumi- 

 nous in life. Many of 

 these species have exces- 

 sively large teeth, and some 

 have been known to swal- 

 low animals actually larger 

 than themselves. Those 

 which have Ian tern -like 

 spots have always large 

 eyes. 



The deep-sea fishes, 

 however fantastic, have all 

 near relatives among the 

 shore forms. Most of them are degenerate representatives 

 of well-known species for example, of eels, cod, smelt, 

 grenadiers, sculpin, and flounders. The deep-sea crusta- 

 ceans and mollusks are similarly related to shore forms. 



The third great subdivision of marine animals is the 

 littoral or shore group, those living in water of moderate 

 depth, never venturing far into the open sea either at the 

 surface or in the depths. This group shades into both 

 the preceding. The individuals of some of the species are 



FIG. 259. A crinoid (Rhizocrinus loxoteri' 

 sis). A deep-sea animal which lives, 

 fixed plant-like, at the bottom of the 

 ocean. 



