16 BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



EXPLANATION OF TERMS. 



The Canthus rostralis is the ridge more or less defined which marks 

 the line of separation anterior to the eye's, between the top and side of 

 the head. The outer nares or external nostrils are situated in or a little 

 below this angular line, and between the eye and tip of snout. The 

 Canthus orbitalis is the corner of the eye, either anterior or posterior. 

 By ramus of jaw is meant either of the two branches, one on each side. 

 The rictus is the point of junction between the upper and lower Jaws. 

 The commissure is the line along which the two jaws meet when closed. 

 The internal nares or choanw are in the roof of the mouth a little ante- 

 rior to the eyes. The Eustachian apertures, or ostia pharyngea, are sit- 

 uated very far back in the roof of the mouth near the end of the jaw, one 

 on each side. The angle of the jaw is just behind the point of articula- 

 tion of the two jaws. The concealed surfaces of the body are those which 

 are internal and pressed against each other when the limbs are flexed. 

 The teeth in the roof of the mouth are vomerine or vomeropalatine when 

 they are within or near the inner nares, and on the bone of same name; 

 and they are parasphenoid, or loosely, palatine^ when considerably be- 

 hind the level of the inner nares and placed on the parasphenoid bone. 



The enumeration of the fingers and toes commences with the inner ones, 

 the fourth finger and the fifth toe being the external. The term finger 

 always belongs to the anterior extremities, and toe to the posterior. 

 The phalanges are numbered from the metapodial bone. By articula- 

 tion is understood the hinge between two adjacent bones, which them- 

 selves are called segments. The tympanum or membranum tympani 

 is the circular disk seen on each side the head, posteriorly and just 

 back of the eye, in the Salientia. 



NOMENCLATURE AND HISTORY. 



By Linnceus, in the tenth edition of the Systema Naturae (1760), in the 

 twelfth (1766), and in the thirteenth (1788) reptiles and batrachians are 

 included in a class "Amphibia." The two classes were not recognized 

 even as subordinate divisions of the Amphibia. These divisions were 

 the Reptiles, Serpentes, and Nantes. The last named included only 

 fishes. Four genera were included in the reptiles, one of which was 

 Rana, which embraced all the Batrachia Salientia. The Urodela were 

 enumerated as species of the genus Lacerta. The genus Coecilia was 

 placed among the Serpentes. 



Laurenti, in the Tentamen Systema Reptilium, 1768, first used the 

 class name Reptilia for a combination of the two classes, Reptilia and 

 Batrachia, as at present recognized. He proposed three orders of 

 Reptilia, the Salientia ( = Batrachia Anura), the Gradientia (= lizards 

 and Batrachia Urodela), and the Serpentes, in which he included the 

 Coecilias. 



Lace^ede, 1788-'90, did not distinguish Reptiles from Batrachia, and 



