THE SESSILE BAENACLES.- 165 



of the cirri. As in the B. balanus group, there is one larger spine 

 near the lower angle of the maxilla, instead of a pair, such as the B. 

 amphitrite group has. 



It is a boreal group, extending into the Temperate Zone. 



Three of the commonest west American species, B. crenatus, B. 

 glandula, and B. hesperius, agree in the rather small size, the dirty 

 white ribbed or smooth wall with ribbed interior, the calcareous, pore- 

 less base, and the short spur of the tergum. The parietes have tubes 

 in B. crenatus, none in B. hesperms, while B. glandula has tubes in 

 some specimens, but wholly filled up in others. They are most easily 

 distinguished by the scuta. 



In B. crenatus there is no adductor ridge, the upper part of the 

 valve being calloused, smooth or roughened. 



In B. glandula a short adductor ridge branches downward from 

 the articular ridge, and there is a pit below their confluence. 



In B. hesperius the thick callous between adductor scar and articu- 

 lar ridge is cut into sharp little ridges. 



B. balanoides is distinguished from these species by its membranous 

 basis, but detached, fragmentary or fossil specimens may be known 

 by the scuta. There is a convexity or rounded callus down the middle 

 of the valve (pi. 45) ; moreover, the parietes are not longitudinally 

 ribbed inside, but have some low anastomosing ridges near the basal 

 edge. 



BALANUS CRENATUS Bruguiere. 



Plates 39, 40. 



1789. Balanus crenatus BRUGUIEKE, Encyclopedic Methodique, p. 168. 



1790. Lepas plicata SPENGLER, Skrivter af Naturhistorie Selskabet, vol. 1, 



p. 167. 



1790. Lcpas fistula SPENGLEK, Skrivter af Naturhistorie Selskabet, vol. 1, 



p. 176. 



1791. Lcpas clongata GMELIN, Syst. Nat., ed. 13, p. 3213. 1 



1799. Balanus ruyosus PULTENEY, Catalogue of the Birds, Shells, etc., of 



Dorsetshire, p. 25 (tubular form). 



1819. fBalanus glacialis GRAY, Suppl. to Parry's Voyage, p. ccxlvi. 

 1841. Balanus ruyosus Pulteney, GOULD, Invertebrata of Massachusetts, 



p. 16, fig. 10. 

 1854. Balanus crenatus Bruguiere, DARWIN, Monograph, etc., p. 261, pi. 6, 



figs. 6f?-6f/. 

 1913. Balanus arcnatus Bruguiere, STEPIIENSEN, Meddelelsor om Greenland, 



vol. 51, p. 71 (North Stroemfjord). 



Type-locality. Coast of England. 



Distribution. Arctic Ocean; North Atlantic south to Long 

 Island Sound; Bering Sea and North Pacific, south to Santa Bar- 



1 1 am. not sure that L. clongata and L. fistula belong to this species. They may ba 

 Balanus balanoides. 



4729 Bull. 93 1( 



