58 SAURIA. 



FAMILY OF CROCODILE^—CR CO DILIByE. 



Head with the snout produced ; body depressed, covered above and 

 below with square shields arranged in longitudinal and transverse series ; 

 each dorsal shield is composed of an osseous dermal scute and of a corre- 

 sponding horny epidermal plate. Tail elongate, compressed. Feet short, 

 more or less webbed. Teeth strong, acute, conical, in a single series. 

 Tongue short, adherent. Nostrils small, situated close together, on the top 

 of the extremity of the snout. Toes 5 — 4 ; only the three interior are armed 

 with claws. 



Freshwater Saurians, found between the tropics wherever the country is watered by suffi- 

 ciently large rivers or lakes. 



The Crocodilians differ in many essential points from all the other Saurians. The pec- 

 toral and abdominal cavities are separated from each other by a muscular diaphragm : the 

 ventricular portion of the heart is divided by a complete septum, so that the oxygenated 

 blood coming from the lungs is not mixed withm the heart with the venous blood ; but a 

 slight intermingling of both kinds of blood takes place in consequence of a persistent com- 

 munication between the two aortse. The teeth are implanted in sockets, whilst in all the 

 other Saurians they are anchylosed to the bone. The penis is simple. These and some 

 other peculiarities have induced many zoologists to consider the Crocodilians either as a 

 distinct suborder of the Saurians (Loricati), or to separate them altogether as an order inter- 

 mediate between the Tortoises and Lizards (Emi/dosauri). 



The most conspicuous characters of the Crocodiles refer to their thoroughly aquatic life ; 

 but these characters are combined with an extremely powerful development of those organs 

 which render the Crocodiles the most formidable of all the carnivorous freshwater animals. 

 The head, terminating in a long flat snout and fastened to the trunk by a short muscular 

 neck, and the longish, depressed trunk, are rapidly propelled through the water by powerful 

 lateral movements of the long, compressed tail. The surface of the tail is enlarged superiorly 

 by a crest, which is composed of a double series of broad lobes in its basal half, and of a 

 single one along its remainder ; these lobes are a sort of caudal web, answering the same 

 purpose as the lobes of the feet of some Grallatorial birds. The limbs themselves are short, 

 and of secondary use for locomotion in the water, and being more or less webbed in the 

 different species, they appear to be mainly for the purpose of preventing these heavy animals 

 from sinking in the soft mud or sand, when they are walking on the shore. The tail is not 

 only the principal organ for locomotion, but, at the same time, a powerful weapon ; and, in a 

 captured animal, much less is to be feared from its teeth than from the strokes of its tail. 



The back, the tail, and the belly are protected by a dermal armour composed of quadran- 

 gular shields, which are arranged in regular longitudinal and transverse series. These 



