Selachians Extraordinary 243 



scheme of classification is a difficult and often frustrating task.'* The 

 basis of any classification system is relationship, and always the classifier 

 is faced with degrees of relationship. One way of stressing this degree 

 of relationship is by gathering species with fundamental structural re- 

 semblances into various groups. One such group is the jafnily . 



Accompanying this text is a list of Selachian families. All the mem- 

 bers of each family have characteristics in common and, in varying de- 

 grees, each family is somewhat more closely related to the famiUes near- 

 est it than to those at greater "distance" in this list (page 244). 



Within the biological boundaries that encompass the entire Selachian 

 super-family is a long array of species. Each species has found its own 

 province in the great realm of the sea. Big or small, fleet or sluggish, 

 cosmopolitan or parochial, each individual Selachian is living as the limi- 

 tations of its specially adapted body compel it to live. 



The species that are described have been selected to present an 

 "Anthology of the Selachian." In the truest sense of the word, this is 

 an anthology— a collection of some of the most interesting and most 

 representative examples of a great natural assembly. 



Most of the common species found in North American waters are 

 included here, along with some that are uncommon and some that are 

 found far from North American shores. Our selection has not been 

 hedged by geographical or ichthyological boundaries, for we wish to 

 present only a selection that will provide a sweeping view of a tremen- 

 dous family. 



It is an elusive family, too, still abounding in mysteries after cen- 

 turies of observation. In two vast areas of the ocean— the numbing cold of 

 polar seas and the profound depths— exists much life we know very little 

 about. In these forbidding outposts of the sea, however, we know that 

 some Selachians carry on their breed. 



In Arctic waters, where the presence of salt allows temperatures 

 to drop below the freezing point of pure water, the little Arctic skate 

 {Raja hyperborea) drops eggs that incubate at 32°F. or below. Off the 

 southern tip of South America, a hardy dogfish {Squahis, species un- 

 known) has been reported venturing into the chill seas bordering on the 

 Antarctic. In 1912, the body of an 8-foot shark was found cast up on 

 the beach of Macquarie Island, some 800 miles from the Antarctic 

 Circle. This shark, though known from only this one specimen, has been 



3 Financial support is needed to make possible the comparison of the preserved 

 species of the larger fishes (and many of the smaller ones) for detailed studv. Much of 

 the confusion in the classification of sharks, skates, and ravs is due to the cost of 

 preserving specimens and making them available for comparison with those captured 

 in other parts of the world. This is a project worthy of investigation and the support 

 of some organization. 



