Phylum - Hemichordata

Explanation

(i) Body of these animals is divided into parts - proboscis, collar and trunk.
(ii) Notochord is present in proboscis region only . Hence, they are called as hemichordates .
(iii) These animals are also called as acorn worms.
(iv) These are marine animals live in burrows in sand .
(v) They have one to many pharyngeal gill slits.
(vi) They are unisexual or some may be hermaphrodite. e.g. Balanoglossus , Saccoglossus