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 gangeticusof 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 schlegeliof 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. tetraspisof 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.2. Nasal bones dividing the nasal groove....Alligator, America and China.
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 gangeticusof 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 schlegeliof 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. tetraspisof 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.
2. Nasal bones dividing the nasal groove....Alligator, America and China.
The genusCracodiluscontains seven species.C. vulgarisorniloticusof most of Africa, is found from the Senegal to Egypt and to Madagascar, reaching a length of 15 ft. It has eighteen or nineteen upper and fifteen lower teeth on each side.C. palustris, the “mugger” or “marsh crocodile” of India and Ceylon, extends westwards into Baluchistan, eastwards into the Malay islands. It has nineteen upper and lower teeth on either side. The scutes on the neck, six in number, are packed closely together, the four biggest forming a square. The length of 12 ft. is a fair size for a large specimen.C. porosusorbiporcatusis easily recognised by the prominent longitudinal ridge which extends in front of each eye. Specimens of more than 20 ft. in length are not uncommon, and a monster of 33 ft. is on record. It is essentially an inhabitant of tidal waters and estuaries, and often goes out to sea; hence its wide distribution, from the whole coast of Bengal to southern China, to the northern coasts of Australia and even to the Fiji islands. Australians are in the habit of calling their crocodiles alligators.C. cataphractusis the common crocodile of West Africa, easily recognised by the slender snout which resembles that of the gavial, but the mandibular symphysis does not reach beyond the eighth tooth.C. johnstoniof northern Australia and Queensland is allied to the last species mentioned, with which it agrees by the slender snout. Lastly there are two species of true crocodiles in America,C. intermediusof the Orinoco, allied to the former, andC. americanusoracutusof the West Indies, Mexico, Central America to Venezuela and Ecuador; its characteristic feature is a median ridge or swelling on the snout, which is rather slender.
The above list shows that the usual statement that crocodiles inhabit the Old World and alligators the New World is not strictly true. In the Tertiary epoch alligators, crocodiles and long-snouted gavials existed in Europe.
(H. F. G.)