B. T. H. Xerxes
Pseudonym of Brian W. Aldiss
"B. T. H. Xerxes" is a pseudonym used in the anthology <a href="http://www.isfdb.org/cgi-bin/title.cgi?35078">"An ABC of Science Fiction"</a>, created so that there would be a story by an author whose name began with "X". The author is probably either Tom Boardman, Jr. (the editor of the anthology) or Brian W. Aldiss. (Information from Robinson's "Who's Hugh"). The limerick about Saturn originated in PITFCS 138 (December 1960) as by Brian Aldiss.