graptolites

Graptolites were planktonic and floated in the upper part of the ocean waters. There external skeleton was made of organic material (chitine). Graptolites formed colonies by asexual reproduction.
Graptolites are seen prodominantly from the Cambrian Period (542 million to 488 million years ago) and that persisted into the Early Carboniferous Period (359 million to 318 million years ago). This Graptolite is from the Silurian.  NSW, Australia.

http://en.wikipedia.org/wiki/Graptolithinia

graptolites

Graptolites were planktonic and floated in the upper part of the ocean waters. There external skeleton was made of organic material (chitine). Graptolites formed colonies by asexual reproduction.
Graptolites are seen prodominantly from the Upper Cambrian through the Lower Carboniferous. This Graptolite is from the Silurian.

http://en.wikipedia.org/wiki/Graptolithinia