Hippopus spp. ID

[acroporas]

I was taking pictures of my clams today and noticed something odd on my Hippopus. Tentacles around the syphon. I assumed it was H. hippopus. But I thought that H. hippopus is not supposed to have tentacles. So is this H. hippopus or H. porcellanus which is supposed to have tentacles.

So what do you think. Is it H. hippopus or H. porcellanus.