154 REPORT OF NEW JERSEY STATE MUSEUM. 



Family BALANID^. 



The Acorn Barnacles. 



No peduncle or stalk developed. Scuta and terga furnished 

 with depressor muscles. Other valves united immovably to- 

 gether. 



Sub-Family Bai^a nin.i;. 



The Acorn Barnacles. 



Shell with rostrum having radii, but without al?e. Lateral 

 compartments all with al?e on one side and radii on the other 

 side. Parietes generally either porose or longitudinally ribbed 

 on inner surfaces. Mouth with labrum notched in middle, not 

 swollen. Palpi large, almost touch each other. Mandibles gen- 

 erally with lower teeth laterally double. Third pair of cirri 

 with segments resembing those of second pair. 



Section Balan^. 



Scutum and tergum articulated together, or overlapping 

 each other. Each branchia composed of a single plicated fold. 

 Genera seven. 



Key to the genera. 



a. Compartments six ; basis calcareous or membranous ; opercular valves 



sub-triangular. balanus 



aa. Compartments six, extremely thick, but one of them, rostrum, composed 



internally of three rudimentary compartments united together ; basis 



membranous ; scuta narrow, united to terga by horny articular ridge. 



CHELONOBIA 



Genus BALANUS Da Costa. 

 The Acorn Barnacles. 



Balanus Da Costa, Hist. Nat. Testae. Britan., 1778, p. 249. Type Balanus 

 porcaliis Costa (:=^Lepas balanus Linnaeus), second species. 



