This train, Seapony Express, is a railcar or multiple unit, not a locomotive-hauled train and the appearance of the front is taken from an Italian littorine/littorina in the interwar period 1918-1939.
The word “littorina” is about sea snails, and in Italy the name of the trains was taken from the lictorial symbol called “fasces”, which was often affixed to these trains which were the fast trains of the time. The word “littorine”, which could be interpreted on a different basis, was a popular nickname for the Italian railcars and multiple units.
In addition, the word could also be used for the nearshore, i.e. the seabed between high and low tide as far as sunlight penetrated the water. This is called the “littoral zone” up to 150-400 m depending on how far down sun-dependent vegetation survives. It gets dark at a greater depth than 400 m.
So this train is a “littorine” intended for travel in the littoral zone - the pirate ship that Izzy and Pipp were abducted to is at greater depths, which could be seen by the fact that the surroundings are much darker, so they are deeper than 400 m.