THE BURROWING BARNACLES (CIRRIPEDIA: ACROTHORACICA ) 35 



curvature supports a single seta. The protopods are two-segmented, of 

 reddish hue, and the proximal segment is at least twice the length of 

 the distal one. The protopods are finely bristled, especially on the 

 inner surfaces. The segment counts of the terminal cirri, for three 

 specimens, follow : 



♦Anterior. **Posterior. 



The caudal appendages arise between and behind the last terminal 

 cirri, being about half the height of the basal segment of the last 

 terminal cirrus. They are uniramous and two-segmented, supporting 

 three or four terminal bristles which are not markedly pinnate, and 

 two or three shorter bristles on the distal end of the basal segment. 



There is no body process in this species, although the thin body 

 epithelium frequently is thrown into what could appear to be pro- 

 jections, especially in specimens boiled in KOH for clarity of chitinous 

 structures. 



The posterior end of the thorax is reinforced by one prominent re- 

 inforcing ring in the epidermis, plus additional foldings of the cuticle 

 which could be the result of body segments, the movements of the 

 body, or for reinforcing the cylindrical epidermis. 



The anus opens on the upper surface between the paired latter 

 terminal cirri, with a rather truncated posterior end of the thorax 

 extending between the posterior three pairs of cirri. 



The posterior thorax bears the very fine striations typical of the 

 order, but to a less pronounced degree (indicated in fig. la). 



The male is 0.87 X 0.43 mm excluding the antennules, and resem- 

 bles a degenerate sac with antennules for attachment typical for the 

 order. A long annulated penis can be seen curling inside the body. 

 The streamlined body is held close to the female or attached exuviae, 

 without the long stalk of some males of the order, A small, deep 

 purple, naupliar eye is present, but no "yellow organ" was differ- 

 entiated from the cellular mass. 



The embryology seems typical for the order. Eggs are retained in 

 the brood chamber behind the thorax. The naupliar stages are under- 

 gone within the egg membrane, and the larvae are retained until the 

 cyprid stage. The cyprids appear typical, with well-developed swim- 

 ming appendages. 



