This intriguing T-shaped animal is a bivalve!
It is the Hammer oyster (Malleus sp.). Thanks to Sijie for finding them on Cyrene Reef recently, and to Chee Kong for identifying them. Once I saw one, I saw lots of them! Talk about search image. Now I must try to find them in our other seagrass meadows. Meanwhile, I've uploaded a fact sheet for this and some other strange snails.
The shells of these snails are commonly seen on our shores, often empty or occupied by a hermit crab. It is rare to see the living animal. Recently, I've been lucky to see live ones!Here's what the animal looks like! Some kind comments on flickr suggest it is the Frog snail, Bufonaria rana. I'm going with Bufonaria sp. as indicated in Tan, K. S. & L. M. Chou, 2000. A Guide to the Common Seashells of Singapore. Singapore Science Centre. 160 pp.
Apparently, one of the distinguishing features of Family Bursidae is the notch at the back of the shell opening (see red arrow).
An interesting fact about these snails is that some species appear appear to feed on tube worms. These have an extendible proboscis and large salivary glands, that are probably used to anaesthetize the worms in their tubes; the worms are then sucked out and swallowed whole. Awesome!
Here's another weird snail that I sometimes see.
It too has a long foot and ploughs through the sand. I have no idea what it is, but from the books, it seems to be some sort of Turrid (Family Turridae).Here's another one I saw. If someone know what it is, I'd love to hear from you.
I finally took the time to sort out some of the little periwinkles that I've seen. They are so small and so common, I confess I haven't been paying them proper attention.
Here's my guesses on what they are...The Black-mouth periwinkle (Littoraria melastonoma) does indeed have a black patch at the mouth. "Melanostoma" means "black mouth". The shell has a nice elegant longish spire.
The Conical periwinkle (Littoraria conica) has a more squat spire and is only found in mangroves.
And the Ridged periwinkle (Littoraria carinifera) has ridges on its shell.
If I've made any errors, please do let me know. I'd be glad to learn and correct.
I should also pay closer attention to the periwinkles!