What is "branchiostoma"

Branchiostoma \Bran`chi*os"to*ma\, n. [NL., fr., Gr. ? gill + ? mouth.] (Zo["o]l.) The lancelet. See Amphioxus. [1913 Webster] ||

n. the lancelet (''Amphioxus lanceolatus'')

Branchiostoma is one of the few living genera of lancelets ( order Amphioxiformes). It is the type genus of family Branchiostomidae.

These small vaguely eel- or snake-like animals are close relatives of vertebrates. The scientific name means "gill-mouth", referring to their anatomy – unlike vertebrates, they do not have a true head (with a skull capsule, eyes, nose, a well-developed brain etc.), but merely a mouth adjacent to the gill-slits, with the slightly enlarged anterior end of the dorsal nerve cord above and in front of them.

Like all lancelets, they are filter feeders that hide in the sediment most of the time. The genus inhabits coastal waters e.g. of the North Atlantic.