THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA ) 111 



than the proximal one. The segment counts of the cirri are as follows, 

 for one specimen: 



Terminal 



cirrus: 12 3 



Ramus: anterior posterior anterior posterior anterior posterior 



Segments: 16 20 22 24 24 23 



The segments bear two pairs of setae on the inner (ventral) curva- 

 ture; with one unpaired seta on the outer curvature of segments up 

 to five segments apart, although at the distal ends of the cirrus they 

 are frequently on each segment. The paired setae on the inner curva- 

 ture are plumose, with about ten very fine curled pinnae on the ventral 

 surface. The setae are essentially of the same size, and have no basal 

 hair arising from the segments between or in front of the setae. The 

 unpaired seta on the outer curvature are faintly plumose. 



The male: A few males have been found, attached to the female. 

 Although care was taken to look, none were found in the burrow. It 

 is not typical to find so few. Two rather poor specimens will be 

 described at this point. 



The first, believed to be a young specimen, was seen with antennules 

 spread in such a way that he could not be turned without distortion 

 (fig. 28o). The paired antennules are typical. The little balls of darker 

 tissue scattered throughout the body made the determination of eyes 

 and yellow organs risky, and so no attempts will be made for this 

 specimen. The antennules were not on long stalks. The body attenu- 

 ated into a clear process posteriorly with a membranous covering, and 

 was broadly rounded anteriorly. No surface ornamentation of any 

 kind was seen. The most peculiar structure noted was a chitinous 

 "beak," unpaired and centrally located ventrally. No function could 

 be deduced for this structure, as it appeared not to be open at the tip. 

 The specimen was roUed over without securing additional information, 

 but its wrinkled condition precluded farther illustration. 



The second specimen was recovered from a female which had been 

 boiled in KOH, so much of the cellular detail was lost (fig. 28n). A 

 definite penis is seen, a pair of antennules are on appreciable stalks, 

 and a curious cylindrical projection of the mantle which could be 

 related to the "beak" is shown. 



The cyprid: The female retains the embryo to the cyprid stage. 

 The eggs and enclosed nauplii appear typical of the order, and the 

 cyprid is typical of the genus. The carapace is ornamented with many 

 individual hairs, and the plates forming the carapace are equipped 

 with numerous spots or pegs arranged in rows which may appear quite 

 regular. The size of the cyprid within the female is about 0.5X0.2 mm. 



