THE SESSILE BARNACLES. 



207 



spines, and there are some short, slender spines near the distal sut- 

 ures. 



Cirri iv-vi are similar, the segments wider than long, each with 

 three pairs of large spines and one small pair. There is a dense tuft 

 of small spines between the first and third pairs. The posterior distal 

 angles of the segments have groups of three or four unequal spines, 

 the longest as long as the segment. On cirrus iv the segments of the 

 pedicel have narrow areas of minute, erect spinules on the distal an- 

 terior part (fig. G6). Following segments have increasingly more 

 extensive spinulose areas anteriorly and along the distal margin 

 (fig. 66e). The inner ramus has fewer spinules. The fifth and 



Fin. 66. BALANUS HAMERI. a, SECOND SEGMENT OF THE PEDUNCLE AND TWO LOWER SEG- 

 MENTS OF ONE RAMOS OF CIRRUS IV ; ONLY THE ANTERIOR MARGIN SHOWN. It, TWENTY- 

 FOURTH SEGMENT OF CIRRUS VI. C, NINETEENTH SEGMENT OF CIRRUS IV, OUTER RAMCS. 



sixth pairs of cirri have fewer spinules than the fourth. The fifth, 

 pair has spinules on the pedicel. The sixth pair has densely spinulose 

 areas on the posterior proximal parts of the segments (fig. 66>, 

 twenty-fourth segment of cirrus vi), but none on the pedicel. 



The penis is as long as the posterior cirri. 1 



B. hameri is easily known from other Atlantic barnacles by its 

 readily separable, thin, externally smooth compartments, poreless 



1 The above details and figures of mouth parts and cirri are from a specimen 43 mm. in 

 basal diameter, from Georges Bank. A young one 13 mm. in diameter is very similar, 

 but with fewer segments 10 and 9 in the raini of cirrus i and with the spiuules far less 

 developed. 



