Tarki (Lattice Fauna)

Tarki is a genus of malleable creatures native to Lattice. There are two species, the spiny-shelled tarki (T. tarki) and the bumpy-shelled tarki (T. smorthus).

Description
Without their shell, it's impossible to tell the difference between the two species of tarki. They both appear as a colored blob with hints of "limbs" along the sides, which they extend and use to drag themselves along. They have two large round eyes with white sclera and small dark pupils, and a small but flexible mouth for chomping down on plant material and raw minerals.

With the shell, telling the two species apart is easy. While the bumpy-shelled tarki has a strong smooth shell with many bumps along the top, the spiny-shelled tarki has a somewhat weaker shell characterized by the huge razor-sharp spikes that jut out of the top.

A tarki's shell is grown over time from local minerals, and for a well-traveled tarki may have many colorful layers on the inside. The gemstone, which is football shaped, is located internally deep within the tarki's flesh.

Behavior
(to be written)

Use by Gems
After a strange incident where a tarki swallowed a gem seed before it could be planted in the ground, it was discovered that tarki make great and highly efficient artificial Gem incubators as long as they're fed the right minerals--their digestive systems cannot break down a gem seed, so it incubates it instead and forms a symbiotic relationship, allowing the gem to be grown above ground with far fewer resources. In some regions on Lattice, tarki farms have completely replaced kindergartens for this reason.

Tarki were also discovered through an unapproved experiment to be capable of incubating Gems that would not be able to grow in a natural environment by feeding the tarki the unnatural combinations of the necessary minerals.

Trivia

 * Discarded and broken tarki shells are commonly mistaken for gem shards.