434 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



I am also indebted to Mr. C. B. Rowland, Victoria, British Colum- 

 bia, whose patience and ingenuity resulted in successful photographs 

 of the living shrimps. I am grateful also to the Provincial Museum 

 of British Columbia for the use of certain facilities and to the National 

 Science Foundation for a grant providing equipment and aid in the 

 completion of the study. Finally, I want to thank my husband, Dr. 

 G. Clifford Carl, for his help in so many ways. 



In addition to the above material I have examined nearly 200 

 specimens (mainly B. longidactylus) from the collection of the AUan 

 Hancock Foundation. I hope to report on this material in a futm-e 

 paper. 



Family Alpheidae 



Rostrum, if present, unarmed. Eyes usually covered by carapace. 

 Mandibles with incisor process and palp of two segments. First 

 pair of legs often with one chela, or both chelae, powerfully developed. 

 Second pair of legs minutely chelate, long, slender, equal, with seg- 

 mented carpus. Telson usually broad, rounded. 



Genus Betaeus Dana 



Rostrum not present; front not spined, either emarginate between 

 eyes or evenly rounded. Chelae usually similar, inverted so that 

 dactyls are on lower side. Telson broad. Sixth abdominal somite 

 with movable plate articulated at posterolateral angle. Epipods on 

 at least first two pairs of leg's. 



Key to Species of Betaeus from West Coast of North America 



1. Dactyli of walking legs slender and simple 2 



Dactyli of walking legs stout and bifid 4 



2. Chelae of first legs with fingers longer than palm. 



B. longidactylus Lockington 

 Chelae of first legs with fingers not longer than palm 3 



3. Blade of antennal scale broad distally. Fixed finger of first cheliped de- 



creasing in width evenly to sharp curved tip . . B. harrimani Rathbun 



Blade of antennal scale narrow distally. Fixed finger of first cheliped truncate 



before sharp curved tip B. ensenadensis Glassell 



4. Front curved, not emarginate B. macginitieae, new species 



Front emarginate 5 



5. Emargination shallow. Telson with posterolateral spines small or missing. 



B. harfordi (Kingsley) 

 Emargination deep. Telson with posterolateral spines well developed . . 6 



6. Peduncle of antennule less than one-half carapace length. Merus of cheliped 



Math lower inner ridge with long bristles, upper ridge ending in sharp tooth; 

 chela with fingers subequal to palm; chela is three times as long as wide. 



B. gracilis, new species 

 Peduncle of antennule subequal to carapace length. Merus of cheliped 

 with lower inner ridge usually tuberculate, upper ridge with tuft of hairs; 

 chela Math fingers longer than palm; chela is twice as long as wide. 



B. setosiis, new species 



