25 
The numbers of species in the various latitudinal subdivi- 
sions are as follows: 
HAC High-arctic circumpolar 44 
HAX High-arctic amphi-Atlantic 5 
HAA High-arctic American 9 
LAC Low-arctic circumpolar 48 
LAX Low-arctic amphi-Atlantic 11 
LAA Low-arctic American 9 
LAEA Low-arctic eastern American 1 
LAW A Low-arctic western American 2 
HSC High-subarctic circumpolar 66 
HSX High-subarctic amphi-Atlantic 6 
HSA High-subarctic American 54 
HSEA High-subarctic eastern American 1 
HSWA High-subarctic western American 7 
L5C Low-subarctic circumpolar 27 
LSX Low-subarctic amphi-Atlantic 3 
LSA Low-subarctic American 56 
LSEA Low-subarctic eastern American 3 
LSWA Low-subarctic western American 2 
