Unknown creature!

[wings]

I am fairly new to the marine aquarium. I have two tanks that have been up and running for 10 months. This morning I noticed something new, and possibly unwanted in my tank. On the side of one of the smooth rocks was a black, flat, half the size of the palm of my hand, seemingly floating across the rock. It settled itself into an indention the size of a half dollar. What is this thing? Could I have gotten this "creature" by hitchhiking. My newest purchases have been two tube amoebas a couple weeks ago.
Also, I have noticed for several weeks, stuck to the sides of the glass, "egg-like" deposits. They are in the shape of an exclamation mark (oval) and white. They are grouped together, five to ten, in a row or half circle. What are these "eggs".
I know I am a "greenhorn", but I seriouosly need information.

 

[nml]

can you post a pic?

 

[perfectdark]

I agree.. pics are the best way to get an ID on anything as there are alot if possibilities based on your description alone.

 

[clown boy]

 

[saltn00b]

sounds like an elephant slug. technically a snail with a very small , usually not visual shell.

 

[sk8shorty01]

Originally Posted by Wings
Also, I have noticed for several weeks, stuck to the sides of the glass, "egg-like" deposits. They are in the shape of an exclamation mark (oval) and white. They are grouped together, five to ten, in a row or half circle. What are these "eggs".
I would take a guess that this is what you are looking for... you can find more pictures under the "common hitch-hiker thread" in this forum. They are called Sand Skaters, and from the looks of things, they do not seem to be a bad thing at all.
Another possible guess would be a hydroid jelly. These are tiny little Jellyfish that attach to the glass, and they actually have little "branches" that are coming off of their center circle. Look closely with a flashlight and see if this could be it.

 

[wings]

No, sorry, I don't have a digital camera.
What about the "elephant slug"? Is this something that I should try to catch. This is, however, the first time I've ever seen it in all these months!