In $Mollusca$,the radula is a part of the:

The mollusc which is considered to be a living fossil and also shows characters of annelids like nephridia and internal segmentation is

$Unio$ has:

In which phylum do some animals possess an open circulatory system while others possess a closed circulatory system?

Apple snail is the common name of .........

Closed circulatory system occurs in