78 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



pletely porous, are more related to B. balanus (with a solid basis) 

 by the characters of the maxillse and terga. A division founded 

 upon the character of the basis would not be natural. The armature 

 of the cirri, the sculpture of the scuta and the shape of the terga 

 are diversified so much, and in combinations so various, that unless 

 the group is to be divided into at least six sections, it had better be 

 left intact. In this opinion I find myself in agreement with Doctor 

 Hoek. 



The interrelations of the species may be shown by a grouping into 

 eight series, of which the first three may be bracketed together, and 

 similarly the last four. 



[Series of B. ampTiitrite. 

 I Series of B. trigonus. 

 (Series of B. perforatus. 



Series of B. gregarius. 



Series of B. aguila. 



Series of B. nubilis. 



Series of B. balanus. 



Series of B. crenatus. 



The following species, not contained in the United States National 

 Museum, belong to this subgenus, part of them being doubtfully 

 distinct from B. amphitrite. Some notes on their characters and 

 affinities are appended. 



Balanus poecilus Darwin. See p. 110. 



Balanus minutus Hoek. Siboga-Expeditie, Cirripedia (p. 177). 

 Entrance of Kwangdang Bay, 80 meters. One specimen on a crinoid 

 pinnule, diameter about 3.7 mm. Pink with reddish stripes. This 

 and B. alatus are similar externally to B. amphitrite, but differ by 

 wanting an adductor ridge in the scutum. From the color,, both may 

 be expected to occur also in shallower water, as the truly deep-sea 

 species are usually white. B. poecilus, alatus, and minutus are alike 

 in having no adductor ridge. 



Balanus Jiystrix Hoek. /Si&o^a-Expeditie, Cirripedia (p. 218). 

 Ambon anchorage, reef. Diameter 5 mm. Third to fifth pairs of 

 cirri armed with recurved teeth on the anterior borders of the seg- 

 ments. It probably stands near B. perforatus. 



Balanus wolaceus Gruvel. Nouv. Arch, du Mus. (ser. 4, vol. 5, 

 1903, p. 133). Locality unknown; type in British Museum. Near 

 B. ampliitrite. It is not Lepas violacea Gmelin, also a Balanus. 



Balanus dybowskii Gruvel. Nouv. Arch, du Mus. (ser. 4, vol. 5, 

 1903, p. 143). Congo. Diameter 6 mm.; no radii. The absence of 

 radii may be due to their removal by the very deep erosion of the 

 surface, which also gives the opercular valves a peculiar shape. It 

 will probably turn out to be closely related to B. ampliitrite or a 

 variety thereof. 



