THE SESSILE BARNACLES. 317 



This species is named for Dr. William IT. Dall, who collected a 

 large part of the Alaskan barnacles in the United States National 

 Museum. 



CHTHAMALUS FISSUS Darwiii. 



Plate 74, figs. 1, la, Ib. 



1S54. Chthamalus flssus DARWIN, Monograph, p. 462, pi. 18, figs. 6a, 6&. 



Type. British Museum, from California, on "Lottia grandis" 



The barnacle is convexly conic or irregular, with the walls rather 

 strongly folded near the base, smooth in the younger stages, covered 

 when unworn with an olive or olive-brown cuticle. Radii, when 

 present, very narrow. Orifice varying from narrow and lengthened, 

 about twice as long as wide, to oval, the length about one and one- 

 half times the width. Diameter about 5 mm. 



The scutum is long; articular ridge not projecting beyond the 

 tergal margin of valve when that is unworn, tapering downward. 

 The adductor muscle pit is deep. Adductor ridge rather strong but 

 short. Pit for the lateral depressor muscle deep. 



The tergum is roughly an equilateral triangle in outline, nearly as 

 wide as long, the basal and carinal borders convex. Articular ridge 

 moderate ; spur extremely short and wide, merely a convexity of 

 the base. 



This species is readily known by the shape of the tergum, which 

 is more shortened than in any other species. I have found it at 

 La Jolla, California, growing on bowlders, Mytilus, and on other 

 barnacles (Mitclla), in the intertidal zone. 



CHTHAMALUS ANISOPOMA, new species. 

 Plate 74, figs. 2 to 2/. 



Type. No. 48198, U.S.N.M., from San Luis Gonzales Bay, Gulf of 

 California, on a stone (Albatross, 1889). 



The barnacle is depressed-conic with a rather long, elliptical ori- 

 fice, closed by the left (rarely the right) scutum and tergum only; 

 radii undeveloped, the sutures distinct and narrow, with finely crenu- 

 lated sutured edges. Parietes strongly, irregularly ribbed. Interior 

 whitish, with a fleshy margin, the basal edges either slightly or 

 copiously roughened with irregular crests (pi. 74, fig. 2e, carina), 

 or quite smooth, except for the fluting caused by the ribs. Diameter, 

 5 mm. 



