BALANINiE. 175 



included in the above table. I have not counted three 

 species, in the genera Alcippe and Conchoderma, which, 

 from the minuteness of their valves, it is hardly possible 

 would be found fossil. On the other hand, I have in- 

 cluded in the 18, five species of Lepas, which from floating 

 and being oceanic, are more likely to be cast up on beaches, 

 than to be imbedded in sedimentary deposits; so that 13 

 would, perhaps, be a safer number, as a standard of com- 

 parison. Now in the coralline crag, which seems to have 

 been eminently favorable for the existence and subsequent 

 preservation of Cirripedes, and which has been so well 

 worked, only nine fossil species, as may be seen in the table, 

 have been as yet discovered. 



Sub-Family — Balanin^e. 



Shell with the rostrum having radii, but ivithout alee ; 

 lateral compartments all having aim on one side and radii 

 on the other side; parietes generally either porose, or longi- 

 tudinally ribbed on their inner surfaces. 



Mouth loith the labrum notched in the middle, not 

 sioollen ; palpi large, almost touching each other ; mandibles 

 geyierally with the lower teeth laterally double ; third pair 

 of cirri with their segments resembling those of the second 

 pair. 



First Section.^ 



Scutum and tergum articulated together, or overlapping 

 each other ; each branchia composed of a single plicated 



fold. 



Genera — Balanus ; Acasta; Elminius; Tetraclita; Pyr- 

 goma ; Creusia ; Chelonobia. 



Second Section. tt 



Scutum and tergum {when both are present) not overlap- 

 ping each other ; basis membranous ; parietes often deeply 

 folded, with the outer lamina, towards the basis, generally 



