Cornelian vs. Carnelian?
As a mineral, the carnelian is the same as the cornelian. Here's a page describing the stone, Cornelian or carnelian. Here are sample pictures from that page:

And here's a carnelian bracelet showing some of the brighter variations in color, from Earthen Vessel Designs.

But Akro appears to have thought the stone was nice enough to name two different kinds of marbles after it!
Here are examples from the Akro section of the ID Guide at Land of Marbles, along with the descriptions:

[indent]
Quote
Akro Agate Co. - Akro Agate 'Cornelian'
Origin: Clarksburg WV
Opaque red swirled with opaque white. Superficially resembles a 'Brick,' but it is not oxblood red.
Origin: Clarksburg WV
Opaque red swirled with opaque white. Superficially resembles a 'Brick,' but it is not oxblood red.

[indent]
Quote
Akro Agate Co. - Akro Agate 'Carnelian'
Origin: Clarksburg WV
One of the 'Ades.' Orange/Brown and opaque white swirls in a translucent fluorescent base.
Origin: Clarksburg WV
One of the 'Ades.' Orange/Brown and opaque white swirls in a translucent fluorescent base.
Here's another Carnelian, this one with oxblood, from a Block auction.

And then there's the M. F. Christensen American Cornelian. This is an old auction photo. I don't know who the seller was:
























