What kind of poem is "A Narrow Fellow in the Grass"?

This is one of Emily Dickinson's more intriguing poems,
written in six quatrains with a regular rhyme in the second and fourth lines alone. The
majority (though not all) of the rhythm is iambic, with the stress falling on the second
syllable of each foot. However, what is more interesting when we think of what kind of
poem this is, is the way in which, like with some other of Dickinson's poetry, it
presents us with a riddle that we need to read the poem very carefully to answer. It is
interesting that the poem never once uses the word "snake," but reading between the
lines we can infer that the poem describes this creature by talking about how it looks
and its habitat, and then recalls a childhood encounter with a snake. The poem ends by
telling us that it is the only creature in nature that causes terror in the
speaker:

But
never met this fellow,

Attended or
alone,

Without a tighter
breathing,

And zero at the
bone.

Note the assonance in
this last phrase, combined with the strong and exact rhyme of "alone" and "bone" brings
a sudden, chilling end to the light tone that came before the final stanza. The snake is
shown as a figure that produces terror in the speaker and ends the poem with a sudden
shock.