STICKLEBACK FAMILY (Gasterosteidae) 



1. Three free dorsal spines; lateral plates developed 



Threespine Stickleback 

 ^ ■ ' ^ ^^"^ ' -'-^.\ Gasterosteus aculeatus 



r>~^ ^'x- / Linnaeus 



More than three free dorsal spines 2 



2. Four free dorsal spines, occasionally with fewer; never with lateral 



plates developed 



^ — -^^^^^^s. Fourspine Stickleback 



^^ J' 3"*^^^ _^^.— ^-^^z' Apeltes qiiadracus 



^ — ^^^= -^^^^^ (Mitchill) 



More than four free dorsal spines 3 



3. Free dorsal spines 5 or 6 



~^— ^^s^x. -^ Brook Stickleback 



f^^ \ - ^'^••^ ^ .y^ !<^ I 



^^ "■■■ .^"-r^^Er Eiicalia inconstans 



^^^^ ^^^ (Kirtland) 



Free dorsal spines 8 to 1 1 



Ninespine Stickleback 



Piiiigitins pungitius 

 ^^ ^"^ (Linnaeus) 



91 



