Arkansaw

The Arkansaw appears in the opening stanza of "The Jack Rabbit:"
In the morning,/ The jack-rabbit sang to the Arkansaw./ He carolled in caracoles/ on the feat sandbars.// 
==What is the Arkansaw?==
According to the US Geographic Names Information System , the Arkansaw is one of the variant names for the Arkansas River. The Encyclopedia Britannica tells us that the river is a tributary of the Mississippi flowing 1,460 miles from its head in the Sawatch Range of the Rocky Mountains in Colorado to its mouth 40 miles northeast of Arkansas City, Arkansas.   
==What is the Arkansaw Doing in this Poem?==
Presumably, the jack-rabbit is hymning the river while turning, or dancing, in small half-circles (since, as the Free Online Dictionary has it, "the caracole is a half turn to the right performed by a horse and rider").  
In the poem, the lively jack-rabbit is juxtaposed against the figure of a black man, who directs his grandmother to sew a buzzard on a shroud, then warns the rabbit of his impending death: "Look out, O caroller,/ the entrails of the buzzard/ are rattling." 
Though the imagery is opaque, it may be that the juxtaposition calls to mind the notion that representation is the death of the actual, or perhaps that the desire to represent (the artist's rage for order) is somehow linked to the death-drive. In this sense, the empty "winding sheet" with its buzzard-image is hungry for the body of the real. 
If this is the case, the Arkansaw becomes a figure of un-versed reality, not unlike the ocean in "The Idea of Order at Key West," while the jack-rabbit is the would-be singer, here pictured perhaps as somewhat naive, unaware--as the black man is not--of the fraught relationship between the real and its image, between language and the thing it names.