BARNACLES OF THE SAN JUAN ISLANDS, WASHINGTON. 



By Henry A. Pilsbry, 

 Of the Academy of Natural Sciences of Philadelphia. 



The Cirripedes noted below were collected by Dr. Carl C. Engberg 

 during 1918 and 1919, partly at Olga, in the Orcas group, the others 

 at Friday Harbor. 



Two species not found by Doctor Engberg have been reported 

 from the San Juan Islands, without special locality — Balanus bala- 

 nus pugetensis Pilsbry 1 and Balanus rostratus heteropus Pilsbry. 2 

 The list is doubtless otherwise incomplete, as it comprises no species 

 of goose barnacles (Lepas), and no Chthamali, small, sessile bar- 

 nacles living on shells, stones, and other barnacles, between tides. 

 As these islands are now frequented by many students of zoology it 

 is thought that a local list may prove useful and may lead to further 

 study of the group, ecological and systematic. 



Figures, descriptions, and references to the literature of barnacles 

 may be found in United States National Museum Bulletins 60 and 93. 



KEY. TO SPECIES. 



a. 1 Stalked barnacles. 



b. 1 Protected by five thin valves ; usually attached to floating objects Lepas. 



b." Protected by many thick valves ; attached to solid objects near low tide. 



Mitella polymerus. 

 a.' Sessile barnacles. 



b. 1 Compartments of the wall penetrated by longitudinal tubes. 8 



c. 1 Ribs on the inner side of the compartments more numerous than the 

 septa between tubes in the base ; tergum long. 

 d. 1 Tubes of wall without transverse septa. 



Balanus balanus pugctensis. 

 d? Tubes of wall having transverse septa, at least above. 4 



Balanus rostratus heteropus. 

 c. 2 Ribs on the inner side of compartments corresponding to septa between 

 the tubes 8 ; basis calcareous. 

 d. 1 Spur of the tergum wide at base, tapering distally, situated near mid- 

 dle of the. basal margin ; large barnacles, up to 100 mm. diameter. 



Balanus n/ubilis. 



1 Bull. U. S. Nat Mus. 93, p. 163. 



* Idem, p. 142. 



* These tubes can be seen by filing the outside, or breaking a compartment trans- 

 versely. In eroded specimens the tubes are often laid open. 



* To be seen by filing the outside. 



* In old specimens of Balanus nubilis the interior is smooth. 



Proceedings U. S. National Museum. Vol. 59-No. 2362. 



Ill 



