THE SESSILE. BARKACLES. 165 



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

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

 ampJiitnte 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. hespeimis, 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. hesperlus^ while B. glandida has tubes in 

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

 distinguished by the scuta. 



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

 val\e 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. halanoides is distinguished from these species Ijy 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 Eruguiere. 



Plates 39, 40. 



17S9. Balanus erenatus Beugui^ke, Encyclopedie Methodique, p. IGS. 

 1790. Lepas pUcata Spengler, Skrivter af Naturhistorie Selskabet, vol. 1, 

 p. 167. 



1790. Lepas fistula Spengler, Skrivter af Naturhistorie Selskabet, vol. 1, 



p. 176. 



1791. Lepas clongata Gmelin, Syst. Nat., ed. 13, p. 3213.* 



1799. Balanus rngosus Pulteney, Catalogue of tlie Birds, Shells, etc., of 



Dorsetshire, p. 25 (tubular form). 

 1819. ? Balanus glaeialis Gray, Suppl. to Parry's Voyage, p. ccxlvi. 

 1841. Balanus rugosiis Pulteney, Gould, Invertebrata of Jlassachusetts, 



p. 16, fig. 10. 

 1854. Balanus erenatus Bruguiero, Dakwin, Monograph, etc., p. 261, pi. 6, 



figs. Qor-Qg. 

 1913. Balanus arenat^is Bruguiere, Stephensen, Meddelelser oni Groenland, 



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 be 

 Balanus halanoides. 



4729°— Bull. 93—16 12 



