Rocktite

Rocktites are Gohma-like enemies that dwell deep within caves. The creature lay dormant atop the ceilings of caves waiting for trains to pass by to attack. When awaken, Rocktites chase and attempt to tackle the intruders. In order to protect his train, Link must use his cannon to fire bombs at the monster's eye in order to slow it down and eventually kill it. If Link is not fast enough the monster will lunge at the train and crush it. After a certain number of hits to the eye it will eventually die.

A certain Rocktite within the Sand Realm is the first of three trials to guard the passageway to the Sand Temple. Its behavior is similar to the first encountered Rocktite but it sometimes keeps its eye shut, leaving its only vulnerable point protected. Link must fire at explosive barrels embedded into the cave walls in order to harm the creature and open its eye.

There are a smaller variety of Rocktites that dwell within caves across Hyrule. These monsters are less of a nuisance as they are killed in one hit with a bomb.

Trivia

 * Though not directly stated, the Rocktite may be related to the Tektite as they both share the characteristics of a single eye and four legs as well as both having the "-tite" suffix in their name. Zelda hints this if Link makes it past the Rocktite in the Fire Realm by stating, "What if all those little ones grew into something like that? ...It's too gross to even think about!".