Shells
Much of Kenji's individual shell collection was donated by his family to the Bishop Museum. Some have been catalogued and entered into the PILSBRy Pacific Island Land SnailBiodiversity Repository (of which the Bishop Museum is a contributor). You can search for Kenji's shells by entering "Yokoyama" in the search field.
Here's a direct link to search for Yokoyama in their database (it will take a few minutes to return results): http://pilsbry.org/collections/list.php?searchstring=yokoyama&reset=0&alldatasearch=1&usethes=1&taxontype=2&db=allspec
Documents
1 / Kenji's Personal Shell Journal
This is Kenji's personal shell journal detailing many of his finds, along with various news clippings that were relevant to him.
2 / Kenji's Shell REference Book
This is Kenji's personal annotated copy of "Pacific Sea Shells" by Spencer Wilkie Tinker, published in 1952.
PDF- Kenji's Shell Book (Pacific Sea Shells, by Spencer Wilkie Tinker, 1952)
3 / Kenji's Shell Labels
This document contains all the shell labels that go along with the collection of shells Kenji donated to the Bishop Museum. All the BPBM-codes relate to the artifact codes in PILSBRy Pacific Island Land Snail Biodiversity Repository