THE SESSILE BARNACLES. 



129 



in number. Segments of anterior ramus less protruding, about 30. 

 The second cirrus has subequal rami, with extremely protruding 

 segments. The third cirrus is but slightly longer than the second. 

 The 21 and 22 segments protrude distally, and bear dense tufts of 

 spines, some of them pectinate near the tips. Fourth to sixth cirri 

 long and slender, of many segments, bearing six pairs of spines, the 



'^.\>^ 



Fig. 34. — Balanus aquila. a, maxilla, and h, mandible op the type. 



lower two pairs quite small. There are also some tufts of minute 

 spines among them, and a rather dense tuft at the posterior distal 

 angles of each segment. Cirrus iv has a regular row of erect spinules 

 along the distal sutures of all but a few extreme proximal and distal 

 segments of the outer ramus. The inner ramus has a feebler de- 

 velopment of them. The second segment of the pedicel is minutely 

 spinulose close to the large anterior spines of the distal angle (fig. 35). 



Pig. 35. — Balanus aquila. a, eleventh segment of cirkcs hi. h, twentt-eighth, 



AND C, SEVENTEENTH SEGMENTS OF CIEBUS IV, ANTERIOR RAMUS. 



The type-specimen, from Monterey Bay in 10 fathoms, was seated 

 upon a rock. The surface is abraded and perforated in places.^ The 



1 The worn condition, together with the peculiar tergnm, led me into the error of placing 

 the species in Darwin's Section A in my original account. The examination of additional 

 perfectly preserved examples and a careful reexamination of the type shows that the 

 radii are not in the least porous. It belongs, therefore, to Darwin's Section C. 



