arthropods

The land mollusks and the great order of insects and other land arthropods only to a minor extent dwell in the open light.

The masticatory organs of Arthropods were jaws disjointed at their symphysis; antennæ, nostrils turned outside in.

So, too, the brain of Arthropods or of Mollusca is not strictly comparable with the brain of Vertebrates.

So we see that the Arthropods, unlike the worms and the Chordata, have obliterated all record of their poor relations.

Limulus, like other water-dwelling arthropods, breathes by means of gills attached to its appendages.