18 



U.S. NATIONAL. MUSiE'UM BULLETIN 271 



Table 3. — Dominant benthic genera of Gammaridea in sublittoral soft-bottom 

 faunule of southern California (+ = yes; 0=no.) 







Kind of domination 



Genus 



Number of - 

 species 







Specific 



Frequency 







Diversity 



of Individuals 



Ampelisca ^ 



12 



+ 



+ 



Byblis 1 



1 







+ 



Ericthonius ^ 



1 







+ 



Eurystheus ^ 



1 







+ 



Heterophoxus ^ 



1 







+ 



Listriella * 



5 



+ 







Metaphoxus ^ 



2 







+ 



Monoculodes ^ 



4 







+ 



Paraphoxus ^ 



18 



+ 



+ 



Photis 2 



5 



+ 



+ 



(Phoxocephalus) ' 



1 







+ 



Protomedeia ^ 



1 







+ 



Synchelidium * 



5 



+ 



+ 



Westwoodilla ^ 



1 







+ 



' Forming limp tubes on or in substrate. ^ Forming stiff or limp tubes on particles or sessile infaunal 

 structures. ^ Burrowers. * Nestler or semicommensal. 



Various other faunules are compiled in table 2. No attempt has 

 been made to modernize certain faunules such as Sars' Norwegian 

 boreal in order to maintain congruency among the reports; thus each 

 faunule presumably represents a minimal statement on diversity as 

 a result of extensive, but not exhaustive exploration. 



Generic domination within a faunule may occur through specific 

 diversity or through high frequencies of individuals in poorly diverse 

 genera. The Californian faunules of tables 2 and 3 thus comprise some 

 dominant genera having numerous species, only a few of which have 

 high frequencies of individuals and other monospecific genera, with 

 extraordinarily abundant individuals per square meter of habitat. 

 Other faunules have been compUed in table 4 on the basis only of 

 intrageneric diversity, as quantitative information is virtually absent 

 except in the California region. These few examples may give the 

 reader an approximation of what to expect in commencing quantita- 

 tive explorations of provinces. 



The ecological kinds of Gammaridea within a benthic faunule are 

 to a large extent determined by domiciliary position rather than 

 food-type, as most Gammaridea are presumed to be scavengers or 

 inquUines and their feeding behavior is poorly known. A few true 

 herbivores apparently occur but only one raptorial predator has ever 



