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A few days ago I found a nice internal & external mold of a rare Arctinurus sp. This is something I've been looking for over 5 years. I was beginning to give up hope having never even found a pygidium in these rocks. Anyway, I decided it would be good to make some internal/external latex casts and molds and show progress here since I haven't seen much on this topic. I am doing this to observe any differences in the internal/external shells since with this type of preservation the skeletal shells have been dissolved during dolomitic diagenesis. The outer shells could possibly exhibit different features not observable in the internal molds ie. taphonomic or morphological, etc. From making comparisons, I don't think it is A. occidentalis as the anterior border projection is not as pronounced. A. nereus more pustulose and lacks anterior tongue. It more closely resembles A. boltoni but I don't think is reported from this area. So, I guess it is unknown...for now unless @piranha can identify it. First cleaned up with scribe and carefully removed the "tongue" from matrix and superglued in place. This appears to be very easy but actually took many hours. Also not shown is the more complicated prep of the external mold which had to be broken into three pieces and trimmed with a tile saw and then glued together. Set overnight. Aside from the Arctinurus, I also am making latex casts/molds of Dalmanites platycaudatus and a Glyptambon verrucosus cephalon. I don't have a lot of external trilobite molds as they usually break apart and lost in the field. This is also my first attempt at making internal latex molds from externals using hydrocal. I have made latex casts from internals with plaster of Paris but with mixed results as it is softer and more easily broken. For these I want high fidelity examples. Also, I am just winging it. Here, applying a very thin first layer of latex to the external Arctinurus mold. The first 4 or 5 layers need to be very thin and dry between applications. I decided to attach the cephalon /pygidium to the dalmanites with clay and aluminum foil to hold both parts together. to be continued...