THE SESSILE BAENACLES. 65 



There is a single specimen of unknown origin in the United States 

 National Museum collection (Cat. No. 43496), which agrees with 

 Darwin's too brief description. The scutum is 8.5 mm. long, the 

 upper 4 mm. more coarsely ridged than usual in this part of the valve; 

 the intervals between ridges are deepened to form a series of shallow 

 pits between the tergal edge and a low rounded ridge or convexity 

 which radiates from the apex, nearer to the occludent than to the 

 scutal margin. The lower half of the valve is ridged as in typical 

 tintinnabulum, without pits. The adductor ridge is acute and rather 

 prominent, about as in B. t. antillensis. The other scutum of the 

 same individual does not show the pits between growth ridges. The 

 tergum is decidedly broader than the scutum, with narrow spur, remote 

 from the basiscutal angle. The orifice is rather large and triangular; 

 parietes weakly striate, the intervals between strias marked with 

 dark violet lines. The wide radii are pale violet. Carinorostral 

 diameter 16 mm., height 13.6 mm. 



This barnacle has a young specimen of Balanus improvisus assimilis 

 Dai-win embedded in the base, suggesting a West Indian or South 

 American habitat. It may prove to be a form of B. t. antillensis, 

 but in the long series of that race I have examined none have pitted 

 scuta. 



BALANUS TINTINNABULUM CALIFORNICUS, ne\ subspecies. 

 Plate 14, figs. 1-3; plate 15, fig. 4. 



Type. Cat. No. 9434a, U.S.N.M., from San Diego, California. 



Distribution. Santa Barbara to San Diego, California. 



Conic, or sometimes tubular, with diamond-shaped or angularly 

 ovate orifice. Parietes rather finely striate, the striae, white on a red 

 (Indian-lake) ground, or some tint of that color; radii similar or paler, 

 sometimes transversely striate near the level summits. Summits of 

 the alse subhorizontal. 



Scutum similar to that of B. t. tintinnabulum, except that the 

 depressor muscle impression is smaller and deeper; adductor impres- 

 sion deep. The external growth ridges show more or less distinct 

 traces of longitudinal striaB, and the outside is largely roseate, not 

 distinctly bicolored as in B. t. coccopoma. 



Tergum rose or partly white, with faint longitudinal striae between 

 the growth-ridges, the spur broad, about its own width from the 

 basiscutal angle. 



The parietal tubes are extremely narrow and numerous (pi. 15, fig. 4, 

 part of the rostrum, with attached vesicular basis on the right) , the 

 septa being very thin and delicate, thereby differing from other 

 forms of B. tintinnabulum. 



Greatest diameter 57 mm.; height 34 mm. The mouth parts and 

 cirri are unknown, the specimens being preserved dry. 



