148 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



these tubes having transverse septa about half way down, the lower 

 half being open. Inside of the parietes sharply ribbed to the sheath 

 (or in some old individuals, becoming nearly smooth above). 



Carinorostral diameter, 55 mm.; meight, 43 mm. (type). 



Greatest basal diameter, 47 mm.; height, 62 mm. (No. 48023). 



The tj 7 pe of this variety was taken by Dall at Unalaska (Cat. No. 

 9202, U.S.N.M.). It is on a very large valve of Placunanomia. 



It differs from B. r. alaskensis by having septa in the upper part 

 of the parietal tubes only, as in B, r. apcrtus, which is a much thin- 

 ner, smaller, and generally rougher barnacle. There are 21 tubes in, 

 the rostrum of this specimen. 



The mouth-parts of the largest specimen in group No. 38670 

 (figured in my former paper, pi. 12, fig. 4), agree with B. r. apertus 

 No. 38667. The third cirrus has no spinules, but there are some 

 minute fimbriuted flat spines and slender sutural bristles as in B. 

 balanus. Some of the flat spines were seen on cirrus v, but none on 

 vi. The largest individual in this group of seven on the shell of a 

 Pecten measures 55 mm. high, 45 mm. in greatest diameter of the 

 base. 



Form suturalis (pi. 38, fig. 3). The Cor win took a peculiar form 

 in Alaska, exact locality not noted, in 1884. It is externally a good 

 deal like typical B. rostratus, as the shape is conic, with small orifice, 

 radii are sunken, parietes with angular edges. Otherwise it is more 

 like dcdli. The Avail is thick, with large square tubes, 17 in one 

 rostrum examined. Interseptal ribs, usually one or two. The tubes 

 are open a long way up ; no septa visible from below. The labrum 

 (fig. 41e) has no teeth. The teeth of the mandibles are unusually 

 acute, but typical in arrangement (fig. 416?). Cirri and penis are 

 substantially as in B. r. apertus, the posterior cirri having segments 

 with seven pairs of spines (fig. 41c). 



The type is Cat. No. 48025, U.S.N.M. 



I have some doubt whether this form will prove separable from 

 B. r. dalli Avhen large series are obtained. A specimen of dalli from 

 Kyska Harbor and one from Plover Bay have very narrow radii, 

 but they are not sunken as in suturalis. 



