Chromodoris heatherae, the red-spotted dorid
Two items of interest, circled in green, shown below in detail.
Flabellina capesis, the white-edged nudibranch
Egg case of the medallion silvertip nudibranch Janolus longidentatus
This nudibranch, a member of a sub-order of the nudibranchs, the dorididae, and thus often called a "dorid", was seen at Sandy Cove at Oudekraal, in fairly shallow water. It was about 15 mm long. It occurs on both sides of the Peninsula, preferring generally waters beyond the intertidal zone, and is most commonly found on rocky walls and under overhangs. It grows up to 40 mm long. It is not uncommon.
Flabellina capensis, the white-edged nudibranch.The second photo shows two items of interest. The one that Victor enquired about is the bottom one, with the question being "Is that a sea creature on the bottom right of the picture or just a symmetrical piece of something? Taken at Coral Gardens." It is a sea creature, specifically, once Victor sent a higher resolution picture, the white-edged nudibranch. It is found on both sides of the Peninsula, usually on reefs with hydroids, on which it feeds. While generally quite small, it does grow to 45 mm, but very few are seen at that size. The "V" formed by the white lines on the oral tentacles and meeting on the head is characteristic.
Egg case of Janolus longidentatus, the medallion silvertip nudibranch.
The silvertip nudibranch is one of the most common nudibranchs in Cape Town waters. Interestingly, there are actually two species which cannot be distinguished visually - you need to see one close to its egg case in order to differentiate them. The "normal" silvertip, Janolus capensis, lays its egg string in a ball, on a branch of a sea fan or, as I noticed recently, the branch of some noble coral. The medallion silverip in contrast lays its string in a disk, on the reef walls. Previously it was thought that medallion silvertips only occurred in False Bay and further east, thus making identification of specimens on the Atlantic side easy: they must have been "normal" silvertips. But, as this egg case shows, and those we have recently seen at Di's Cracks and Star Walls, this is not correct.
Nudibranchs of Southern Africa - a guide to the opisthobranch molluscs of southern Africa, T Gosliner, 1987.