THE SESSILE BARNACLES. 



73 



cated or slightly overhaiiging. A ridge runs downward from, it, 

 bord(»ring the deep pit of the lateral depressor muscle, but there is no 

 adductor ridge. Pit for the adduetor muscle is well marked. 



The tergum has the longitudhial furrow more or less open. Spur 

 rather short, with rounded end, situated about its own width, more 

 or less, from the basiscutal angle. jVi-ticular ridge strong. There 

 are no crests for the depressor muscle. 



Compartments. — The parietes are typically smooth, but in some 

 conic, sohtary individuals they have rather numerous ribs. The 

 radii are wide, with level summits. The lateral edges of the radii 

 and the opposed sutural edges are rather coarsely septate, but the 

 septa are either not distinctly denticulate, merely a little irregular, 

 or there may be a few coarse denticl:>s on ona side (fig. 12c). The 

 hoiizontal pores of tlie radii are well developed. 



Fig. i:i.— B alanus algicoi.a. a, maxilla. 6, 1-4th segment of cirrus vi. c, mandible, d, more enlarged 



THIRD TOOTH AND LOWER POINT OF THE MANDIBLE. 



The basis is not very thick. It is radially porous, without a cel- 

 hdar under-layer, so far as seen. 



The labrum has thi'ee minute teeth on each side. The mandible 

 has three strong teeth, the fourth and fifth being quite small and 

 short (fig. 13c, d). 



The maxilla has 8 to 10 large spines. The margin protrudes some- 

 what toward the lower border (fig. 13a). 



The cirri are puiple. The first three paire are quite short, as in 

 tintinndbulum; the later ones are not very long, and have segments 

 a little wider than long. The sixth pair has rami of about 22 segments 

 with from six to eight paire of spines on tlie middle segments (fig. 

 136). I could find no spinules along the distal borders of the segments, 

 such as other races of B. tintinnahulum have. 



