An articulated Trilobite to print and assemble. (If you like Trilobites - have a look at 4MULE8's beautifully organic Comura Articulatum http://www.thingiverse.com/thing:60521 )
Unlike the fossil ones you see in museums, you can have fun flexing and rolling this trilobite up - bit like a woodlouse (or pill bug.) It makes a satisfying clacking noise if you ripple the segments.
You can make baby trilobites by using just the smaller body sections. Whole trilobite families, or even armies, can be yours for the printing.
This creature is very inquisitive and can often be seen peering over people's monitors or shoulders.
Jasonwebb has done a short video (with sound) showing it moving http://vimeo.com/47692125 and Busybotz has kindly included it in one of his excellent 3D printing videos www.youtube.com/watch?v=LGNg37Fc584 (starts at ~3:08) and http://3dprintblog.blogspot.co.uk/2012/09/3d-printed-parts-assembled-and.html (starts at ~1:45).
I'm thinking about other designs of body (with spikes), head (more plate-like, and with more spines) and tail (spikes, and more spikes). Comura looks fun http://en.wikipedia.org/wiki/File:WLA_hmns_Trilobite_Comura_sp.jpg
If you're interested in trilobites, Richard Fortey's book "Trilobite! - eyewitness to Evolution" ( www.amazon.co.uk/dp/0006551386 ) is a great read; and I found http://www.trilobites.info/ fascinating, especially the eyes section http://www.trilobites.info/eyes.htm
I've included a photo of the fossil trilobite that gave me the idea to make a stylised, flexible version.
Print "Trilobite Head 2", "Tail" and TWO lots of "Body" (8 body segments arranged in a row). On our Replicator, 20% infill and two shells (to make the pegs stronger), with ReplicatorG defaults worked well. Apart from the head, none of the parts need a raft (they're all flat on the underside). On the head, only the two pegs might need support.
Note: If you're printing in PLA (or on a Replicator 2), try the STLs in "Tighter_trilobite.zip" - there are a set of test peg/sockets to print in "pegs_test.stl" [Thanks to dethcookie for help with testing.]
It's probably best to print as scaled in the STLs - which gives a width of ~8cm and a total assembled length of ~17cm. You can print smaller and larger, but the joints may need a little fettling.
Note: Different colours of plastic might give loser/tighter joints - on our replicator, ABS orange/white/black were fine, ABS pink was looser but held together.
Let the parts cool down; then starting with the tail and one set of body parts, clip in the smallest body part, then the next biggest, etc... Repeat with the second set of body parts in reverse order (i.e. biggest to smallest), and finally the head. If you want to swap them around, the parts should unclip (carefully).
Note: I've also included the eight individual body parts in a ZIP; and STEP and Parasolid versions of the whole trilobite (just in case someone wants to add more spines or fiddle.) NB the STLs are 1.5x scaled up from the other models.
For laird, I've also added just the peg-and-socket part - ready for exciting spikes and other paraphernalia to be added... The curved surface is the top.