_Reptiles._--These are much less known than the preceding classes, but they afford several peculiar and interesting forms. Snakes are perhaps the least remarkable; yet there are recorded 4 peculiar genera of Calamariidæ, 1 of Colubridæ, 1 of Homalopsidæ, 3 of Dipsadidæ; while _Boa_ and _Elaps_ are in common with South America. Lizards are much more specially developed. _Chirotes_, one of the Amphisbænians, is confined to Mexico and the southern part of the Nearctic region; _Heloderma_ forming a peculiar family, Helodermidæ, is Mexican only; _Abronia_ and _Barissia_ (Zonuridæ) are also Mexican, as is _Siderolampus_ belonging to the Scincidæ, while _Blepharactitis_ (same family) inhabits Nicaragua; _Brachydactylus_, one of the geckoes, is from Costa Rica; while _Phymatolepis_, _Lamanctus_, _Corytheolus_, _Cachrix_, _Corythophanes_ and _Chamæleopsis_, all belonging to the Iguanidæ, are confined to various parts of the sub-region. In the same family we have also the Antillean, _Cyclura_, and the Nearctic _Phrynosoma_ and _Tropidolepis_, as well as the wide-spread American genus _Anolius_. Among the tortoises, _Staurotypus_, allied to _Chelydra_, is found in Mexico and Guatemala; and another genus, _Claudius_, has been lately described from Mexico. _Amphibia._--These are chiefly Batrachians; _Rhinophryna_ (forming a peculiar family) being confined to Mexico; _Triprion_, a genus of Hylidæ, inhabiting Yucatan, with _Leyla_ and _Strabomantis_ (Polypedatidæ) found only in Costa Rica and Veragua, are peculiar genera. The Salamandridæ, so abundant in the Nearctic region, are represented by a few species of _Amblystoma_ and _Spelerpes_.