Considering the interest which is taken in crocodiles and their allies, on account of their size, their dangerous nature and the sporting trophies which they yield, the following “key,” based upon easily ascertained characters of the skull, is given.
I. Snout very long and slender. The mandibular symphysis extends backwards at least to the fifteenth tooth.
(a) Nasal bones very small, and widely separated from the premaxilla (which encloses the nostrils) by the maxillaries which join each other for a long distance along the dorsal mid-line.... Gavialis gangeticus of India, the “gharial” or fish-eater.
(b) Nasal bones long, so as to be in contact with the premaxilla at the hinder corner of the nostril groove.... Tomistoma schlegeli of Borneo, Malacca and Sumatra.
II. Snout mostly triangular or rounded off. The mandibular symphysis does not reach beyond the eighth tooth.
(a), The fourth mandibular tooth fits into a notch in the upper jaw. Crocodiles.
1. Without a bon nasal septum between the nostrils.... Crocodiles.
2. The nasal bones project through the nasal groove, forming a bony septum. Osteolaemus frontatus s. tetraspis of West rica.
(b) Fourth mandibular tooth fitting into a pit in the upper jaw. Alligators.
1. Without a bony nasal septum.... Caiman, Central and South America.