Hi James,
The 31st species of garter snake was described in 2000, but it was just officially recognized last year (2006). You can find a complete listing for the 31 species here (
Species Guide - gartersnake.info). Though it's not an "official" website, the listing is current and accurate.
Thamnophis marcianus bovallii remains a subspecies... found in Nicaragua. I noticed that we have 32 listed on our caresheets page (
http://www.thamnophis.com/caresheets...itle=Main_Page), but
T.s. tetrataenia is included (and properly designated as a subspecies) because of its "special" status. Let us know if you'd like more info.
Rick