The Maya Mountains horst of British Honduras, is collinear with, and probably geologically related to, the Cayman Ridge in the Caribbean Sea. It contains one batholith of highly differentiated granite (Mountain Pine Ridge batholith) with Rb/Sr values of 8 to 16, and two modal muscovite granodiorite batholiths (Hummingbird and Cockscomb) with Rb/Sr values of 0.5 to 3.6. The Mountain Pine Ridge batholith is a true granite and is modally and chemically distinct from the dominantly granodioritic post-Jurassic intrusive rocks of the Caribbean and Central America. The Hummingbird and Cockscomb batholiths, although identical to the post-Jurassic rocks in relative quartz–plagioclase–alkali feldspar abundance, contain modal muscovite, which, along with the high K2O and SiO2 contents of the batholiths, distinguishes them from the post-Jurassic rocks. The absence, from recent dredge hauls, of granitic material similar to British Honduran granitic and granodioritic rocks precludes the use of these submarine granitic exposures as definite evidence for pre-Jurassic crust in the submarine part of the Caribbean region.