Identifying Shells

I have spent some time on the internet trying to more specifically identify the shells I picked up on Hilton Head Island. I knew the general categories such as whelks, clams, oysters, gastropods but now I have a better idea of what kind of clams for example. Also, there were a few which were totally unknown to me. I found a very helpful picture index online. Using that and the written descriptions, here is what I discovered.
 Most of my shells are probably incongruous ark clams. These were the most plentiful on the beach.
 Some might be blood arks as they have very thick shells.
       Oyster and coquina shells also fairly common.
 I have no whole knobbed whelk but quite a few large pieces. Most have shiny colored “linings”.

 I think I have an Atlantic bubble shell, but part of mine is broken off so I am not sure.

One stout tagelus.

 One of my favorite finds is the heart cockle because of the rosy inner color.
 I knew these were some kind of snail when I picked them up; they are called Shark’s Eye or Moon Shell.

 I have one yellow cockle.
 I am pleased to learn that this paper-thin white shell is a channeled surf clam or duck clam. I have a whole undamaged one which is somewhat rare because of the fragility of the shell.
 Originally I thought the pieces of holey items I picked up were just eroded; now I learn that these are probably pieces of dead coral.
 These almost translucent tiny shells were a mystery to me. Turns out they are jingle shells.

I have a few pieces I am not sure about even after looking at the photos. They are too small or incomplete. One is the top of a whelk shell, but it could be channeled whelk or knobbed whelk. It looks almost like a gray toy top. Have you done beach combing? What did you find?