THE SERSTLE BAKNACLES. 



187 



joints, respectively, also strongly protuberant in both rami. The 

 third cirri have longer and more slender rami of IG and 15 joints, 

 ^vhich protrude moderately in front. The anterior ramus is the 

 longer by about 3 segments. First joint of the peduncle is broad. 

 Most or all the segments have some minute multifid spinules, and 

 toward the base there are some simple spinules near the anterior 

 margin (fig. 386?, seventh segment). The fourth to sixth cirri have 

 patches of spinules near the distal anterior angles of both segments of 

 the pedicel. Cirrus iv has a few spinules on part of the segments 

 of both rami (fig. SSh). Cirri v and vi have a few short, erect, spike- 

 like spinules along the distal borders of part of the segments (fig. 

 38«, seventeeuth segment of cirrus vi), and four pairs of anterior 



Fig. 38. — Balanus plos. a, 17th segment of cirrus vi, outer ramus. l>, 14th seg- 

 ment OF OUTER ramus CIRRUS IV. C, TTH SF.GMENT ANTERIOR RAMUS OF CIRRUS III. a, 

 AND b FRO.M A PARATTPE ; C IROM HUMBOLUT BAY. 



spines. A few median segments of cirrus vi have a minute fifth 

 pair. There are about 3G segments in the rami of cirrus xi. The 

 posterior distal angles of the segments have a group of unequal 

 spines, the longest about two-thirds the length of the segment. 



Some of the spines on all of the cirri are pectinated near the end, 

 but the pectination is best developed on the third cirri. In figure 

 38c the pectinated ends of some spines of the posterior ramus of 

 cirrus iii may be seen projecting beyond the anterior ramus. 



The penis is rather short, as in B. haXanus, less than half as long 

 as the sixth cirri, not hairy, and has a small projection near the 

 dorsal base. 



In some individuals the sculpture of the scutum has more the ap- 

 pearance of narrow, very low ridges, separated by much wider flat 

 intervals. Under a strong lens there are very faint traces of radial 

 striation, not visible in all cases. 



