180 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



but their place is taken by long spines, as in B. balanoides. This 

 differentiates B. glandula from B. crenatus, which has the anterior 

 part of the segments of the third cirri set with short spinules. 



B. glandula may most easily be distinguished from B. crenatus 

 by the presence of a short adductor ridge in the scutum, with a con- 

 spicuous pit, like that for a muscle, below the confluence of the ad- 

 ductor ridge with the base of the articular ridge. The very short 

 broad spur of the tergum is also characteristic. In B. hcsperius 

 there is a prominent rugosity between the adductor muscle pit and 

 the articular ridge, which is wanting in B. glandula. All of these 

 species, together with B. l>alanoides, have terga of the same general 

 appearance, and the mouth parts and cirri do not differ very conspic- 

 uously. 



V 



The pores in the basal edges of the parietes are irregular, not devel- 

 oped between all of the ribs of the interior; when developed the 

 inner lamina of the wall does not reach quite to the base. In full- 

 grown barnacles a few narrow pores may usually be found deep 

 between some of the basal ends of the ribs, which are crenulated and 

 unequal; but in some specimens they are wholly filled up, as in B. 

 bdlanoides. 



I take San Diego to be the type-locality. Plate 43, figures 1 to 3, 

 represent specimens from there. The shape is conic or convexly 

 conic, and the aperture is small in all the specimens seen. 



At La Jolla, California, I found B. glandula on rocks near high- 

 tide mark, with Mitella polymerus and Chthamalus fissus. 



In a group of nine individuals from San Francisco the shape is 

 more cylindric, and the walls are much more weakly ribbed, or in 

 some not at all ribbed. Aperture larger. 



A Puget Sound series, on valves of Mytilus, contains strongly 

 ribbed, typical individuals, with others of a more cylindric shape, 

 with very weak ribs and large orifice. One is 13 mm. in basal diam- 

 eter, 12 mm. high. 



At Union Bay, Bajaie Sound, British Columbia, elongated columnar 

 individuals occur with a shorter, obliquely conic form, growing upon 

 the large ones. In some of the shorter individuals the opercular 

 valves are unusually long, the tergal margin of the scutum decid- 

 edly surpassing the basal margin, as in figure 57#. The radii are 

 rather wide in some of this lot, but the compartments are thin and 

 weak (fig. 57). 



At Sitka the strongly ribbed conic and the smoother, short, cylin- 

 clric forms occur. The largest individual measures 16 mm. in basal 

 diameter, 13 mm. high. Cirri and mouth parts as described by 

 Darwin. See plate 43, figs. 5, 7, 7a. 



