Dear Wilhelm,
Thanks for another interesting message. Yeas this is definitely Terry's Ancula sp. 1. I'm pretty sure it has not been named as yet. Of particular interest is why the large animal and the smaller ones are all aggregated together. From you whole photo - which I haven't included - they are on a large sponge colony, but as you can see in these close-ups, the whole sponge is covered with a closely packed colony of kamptozoa. Have a look at the Fact Sheet I have recently prepared on these strange little animals, which are the sole food item of the related nudibranch genera Trapania. Your photo is very interesting, because we have no good evidence on just what the food of Ancula is. Ancula gibbosa is said to feed on compound ascidians, but Bernard Picton thinks they may feed on kamptozoa. Your photo is pretty strong evidence that this South African species definitely feeds on kamptozoans

Now to the animal [middle right photo] from your earlier message. It is indeed Thecacera penngera. Apart from colour differences the two genera differ in the decoration around the rhinophores. In Ancula there is a bifid papilla on the outside of each rhinophore stalk while in Thecacera there is a large rounded cup. Now that we know about the food of Ancula and easy field clue to which is which would be to note where they are found. Species of Thecacera, like species of Polycera, feed on bryozoans, so are likely to be found wit other polycerids.  On the other hand, Ancula is likely to be found on sponges, or some other place where kamptozoans can be found. Not that useful if you find one crawling across a rock, but both polycerids and goniodorids are often found on their food.

Best wishes
Bill Rudman