116 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



The radii vary in width, but have oblique summits, so that the 

 orifice, especially in the more tubular examples, is toothed. The 

 parietal tubes are very numerous, 29 in the rostrum, and are pro- 

 vided with many transverse septa throughout their length. The 

 interior is ribbed only very close to the base. The sheath is colored 

 like the outside. 



The base is porous, but often irregularly, large parts of it being 

 poreless. Darwin states that there are no pores in a South African 

 specimen he examined. 



Greatest diameter 20 mm.; height 10 mm. (conic). 



Greatest diameter 17 mm.; height 15 mm. (conic). 



Greatest diameter 16 mm.; height 18 mm. (tubular). 



The labrum has three teeth on each side (fig. 29a). 



FIG. 29. BALANUS SPONGICOLA, EXMOUTH. a, LABRUM. 6, HTH SEGMENT OF CIRRUS vi. 



C, ANTERIOR PART OF AN INTERMEDIATE SEGMENT OF CIRRUS in. d, MAXILLA. 



The mandible is like that of B. concavus, figured on p. 106, fig. 26&. 



The maxillaB (fig. 29d) has eight spines between the upper and 

 lower large pairs. There is also an inserted spine between those of 

 the lower pair, and another below them. The edge is rather even. 



Cirrus i has rami of 19 and 12 segments. The posterior ramus is 

 about three-fifths as long as the anterior and has moderately pro- 

 tuberant segments not nearly so long as in B. concavus. Cirrus ii 

 has 14 and 15 segments, but the anterior ramus is a trifle longer. 

 Cirrus iii has rami of 15 and 13 segments. On the anterior ramus 

 the third to thirteenth segments are armed as shown in fig. 29c, but 

 vary in the number of " teeth." The posterior ramus has the fourth 

 to eighth segments similarly armed. I see no teeth on cirrus iv. 

 Cirri v and vi have most of the segments with three pairs of spines, 

 but there are four pairs, the lower very small, on a few segments. 



The penis is extremely long, as in other species of this group. 



