THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA ) 99 



bears hairy margins. The mouthparts consist of the usual pairs of 

 mandibles with palps, first and second maxilla. The mandibles bear 

 the usual three teeth with finer teeth between. A distinguishing feature 

 is the prominent notch which separates the anterolateral tooth from 

 the others (fig. 25e). The first maxillae are typical, with heavy bristles 

 rather than teeth, and with the usual apodeme. The second maxillae 

 are typical of the order. 



The mouth cirri are so small as to be barely noticeable. The few 

 thin bristles on a raised hummock are all that remain, and whether 

 they are functional or vestigial is open to question. 



The posterior thorax is finely creased with striations caused by 

 corrugations in the cuticle. The anal region bears a chitinous rein- 

 forcing with striations slightly more prominent. 



Three pairs of biramous, multisegmented terminal cirri crown the 

 thorax. They are set on a two-segmented protopod, with somewhat 

 fewer hairs on the protopod than seems typical. The segment count 

 for the three terminal cirri are as foUows: 



Terminal 



cirrus: 12 3 



Ramus: anterior posterior anterior posterior anterior posterior 



Segments: 9 15 17 18 20 20 



Each segment bears two pairs of bristles on the inner curvature, 

 while each one to four segments along the outer curvature bears a 

 single bristle. All bristles are about of the same length, and slightly 

 plumose. No caudal appendage is present. 



The dorsal side of the thorax bears two filamentary body processes, 

 not paired. The anterior process appears to be slightly larger in this 

 species. 



The esophagus leads directly dorsal from the mouth, then takes a 

 bend posteriorly to the gizzard. The gizzard is typical for the genus — 

 a muscle-supporting framework with two split hemispheres of rounded, 

 tubercle-bearing, grinding plates, followed by what appears to be a 

 finer triturating mill. 



The larvae are retained to the cyprid stage. The cyprids are typical 

 of the genus, appearing essentially as that shown for the larval male 

 (fig. 25g), but with many rows of roughly rectangular plates in the 

 carapace, each bearing about 20 projecting pegs arranged in rows and 

 geometrical patterns. The larval male also had these peg plates, but 

 they were much less apparent. The antennules are set on jointed proc- 

 esses, with the "elbow" demonstrating a chitinous curlicue internally. 



The males are not unusual. They possess a hyaline mantle without 

 peg plates, with a prominent penis, and a pair of antennules. The 

 posterior end is bifid, with about four small teeth. The presence of 



