Biradial symmetry and lack of cnidoblasts are the characteristics of

All organisms of this phylum exhibit bioluminescence.

Name an animal that exhibits the phenomenon of bioluminescence and mention the phylum to which it belongs.

Identify the phylum which shows the following characteristics:
$1$. Animals are exclusively marine,radially symmetrical,and diploblastic.
$2$. Body bears eight external rows of ciliated comb plates which help in locomotion.
$3$. Digestion is both extracellular and intracellular.
$4$. Reproduction is only by sexual means.

Why is $Ctenophora$ considered a minor phylum?

Bioluminescence is well-marked in which of the following phyla?