Horror Stories was a pulp published by Popular Magazines beginning in 1935. It ran fro 47 issues. Here's a selection of covers from 1935-1941. Some of my more favorite story titles are: "Satan Sends a Rat" and "Death Calls from the Madhouse."
Illustration by J. Allen St. John for "Perils of Dragonia." This story by Mollie Claire appeared in the April 1949 issue of Fantastic Adventures. The giant horse has wheels on his feet.