And they told us that the shells were the external skeletons of the tiny, soft creatures inside.

Most of their taxonomic characters are evident in the external skeleton.

Invertebrates don't have a skeleton of bone, either internal or external.

During their 17 years under the earth, they molt their external skeletons five times.

Octopods have no internal or external skeleton, allowing them to squeeze through tight places.

In terms of having bigger brains, arthropods are, as we have seen, limited by their external skeletons.

The external skeleton has one incidental quality which has had momentous results.

All three sections are enclosed within an external skeleton made, primarily, of chitin.

The chitinous external skeleton seems to be particularly responsive to the demands of evolution.

An external skeleton, however, is also an unexpandable prison.