156 



BULLETIN 9.'!, UNITED STATES NATIONAL MUSEUM. 



of the antei-ior ramus, as far as the twelfth segment. On the pos- 

 terior ramus there are fewer spinules, and fewer segments. On the 

 fourth cirrus there are a few spinules, chiefly of the flat multifid 

 form, in a row near the distal sutures of the segments. There 



Fig. 44.- 



-BALANUS EALANUS from ABERDARE CnAXXEL. 

 THREE INDIVIDUALS. X 



a, SCDTUM AND b, C, (I, TERGA OF 



are many erect, mainly simple spinules on the second segment of 

 the pedicel. Cirrus iv has minute, flat multifid spinules on the distal 

 parts of the segments of both rami. In cirrus vi the segments of the 

 pedicel have many minute, multifid spinules, but there are none on 



the segments of the rami. 

 These have 40 segments, bear- 

 ing six pairs of sphies. The 

 fourth and part of the segments 

 of the fifth cirri have five pairs 

 of spines. The penis is typical 

 except that I can find no trace 

 of the point near the hase^ char- 

 acteristic of B. halanus. The 

 individual dissected is certainly 

 adult, the largest of a consider- 

 able series (fig. 45). 



The habit of this colony is to 

 grow in branching groups, un- 

 like the usual colonies of B. 

 halanus. 



Greenland (Upernavik) speci- 

 mens attain a good size, 44 mm. 

 in diameter and height. Ribs as in typical B. halanus but weaker, 

 often hardly noticeable. Tubes of the parietes large. Beak of 

 the tergum white. Darwin also has noted that in Arctic specimens 

 the terga have white beaks. 



Labrador specimens from GO fathoms are deficient in ribs, with 

 the aperture as large as the base. The terga and sometimes the 



Fig. 45.— Balanus balanus, Aberdare Channel. 



a, base of CIRRUS VI "WITH penis. 6, PART OF 7TH 

 SEGMENT OF ANTERIOR RAMUS OF RIGHT CIRRUS III. 

 C, 32d SEGMENT OF CIRRUS VI. 



