Weird hitchhiker. Calling the experts.

[danbe]

I found this on my glass tonight (up close to the top). It is about 3/4" long and 1/2" wide. It is not round, shaped more like a sea shell. It doesn't look like it is hard on the outside. If I had to describe it it looks like a soft clam. It hasn't moved and appears to be stuck to the glass by the outer skin, no arms, legs, suction cups, etc. Is it some type of egg sack? I have included pictures.
Thanks

 

[coraljunky]

Looks like a clam to me.

 

[tangwhispr]

maybe a slipper clam, if its soft its prolly just a slug, can you get a better picture?

 

[lexluethar]

Looks like a peanut to me

 

[danbe]

bump

 

[dempseyjosh]

anybody know for sure what it is? i found one of these in my tank yesterday
anybody know if it is fine to leave in or if i should take it out

 

[zeke92]

it's kinda cute. i'd buy it, hehe, especially if it's a filter feeder. ;ike a clam