4 UNITED STATES NATIONAL MUSEUM BULLETIN 29 6 



of barnacles from the National Institutes of Health, United States 

 Public Health Service, number GM-09953. 



Special thanks are due my wife, Jean, who typed the manuscript 

 and was helpful in many other ways, and to William A. Newman 

 who gave suggestions on the manuscript. 



Abbreviations Used in the Figures 



AN Anus 



ANT Antennule 



AP Aperture in the shell 



APO Apodeme 



ATR Atrium of oviduct 



BP Body process 



CA Caudal appendage 



CC Comb collar 



CE Cyprid eye 



CF Caudal furca 



CM Mantle cavity 



EMF External mantle flap 



ESO Esophagus 



G Gizzard 



H Head 



HD Horny disk 



HK Horny knob 



I Intestine 



IG Infra-esophageal 

 gangUon 



LA Labrum 



LAR Larva 



LB Lateral bar 



LBT Lateral bar termina- 

 tion 



Detailed labels on figures 1 and 23. 



MAN 



MAN.P 



MAXi,2 



MC 



MP 



NE 



O 



OK 



OP 



PB 



PE 



PO 



RC 



RO 



S 

 SG 



STO 



SV 



TC 



TE 



YO 



Mandible 

 Mandibular palp 

 Maxilla (first and 



second) 

 Mouth cirrus 

 Mouthparts 

 Naupliar eye 

 Ovary 



Orificial knob 

 Operculum 

 Protuberant button 

 Penis 



Orificial palp 

 Retractor corporis 



muscle 

 Retractor orificii 



muscle 

 Sperm 

 Supra-esophageal 



gangUon 

 Stomach 

 Seminal vesicle 

 Thoracic cirri 

 Testis 

 Yellow organ 



Methods 



When a specimen of the order Acrothoracica is found, it has to be 

 removed from the shelly matrix into which it has burrowed before it 

 can be studied in detail. Often the specimen itself will not be seen 

 from the surface of the shell. The females can pull into the burrow for 



