Barnacles Found Along the James River. Can They Be IDed to species?

[Isopedia]

Two species? Photos for specimen one are 1-7 and photos for specimen two are 8-13.

[Fossildude19]

@MarcoSr  @Al Dente  @MikeR

[shark57]

Look up Balanus concavus. I believe both of these are the same species, with the smaller ones being younger versions of the larger ones.

[Al Dente]

7 hours ago, Isopedia said:

Two species?

I don’t know the answer. Usually it is the inner valves (tergum and scutum) that are used to ID barnacles to the species level, but if one is familiar with the site and species present, external characteristics could be used. Image from here-https://hozir.org/fig-1a-balanus-tintinnabulum-nat-size-small-specimen.html