1^0. 646] THE PHYLOOENY OF TEE CAUDATA 425 



The extreme antiquity of the Caudata can be readily 

 seen when an end form, a river adaptation, is found in 

 Oligocene times. 



This of course puts the origin of the main stocks back 

 at least to the end of the Mesozoic, a conclusion to which 

 the distribution also forces us. 



The primitive characters appear in widely scattered 

 and rather unrelated forms. The free prearticular has 

 already been mentioned. A free lachrymal is found in 

 Hynobiidce and in an Ambystomid, BJiyacotriton. A 

 postfronto-squamosal arch is found in one group of the 

 Salamandridce. A T-shaped parasphenoid is found in an 

 Ambystomid (Dicamptodon) and in a Salamandrid 

 {Tylototriton). Long maxillae are found in the two 

 forms just mentioned and in another Salamandrid, 

 Pachytriton. Posteriorly projecting pre vomers are 

 found in Amphiuma, in all Salamandridce, in some Hy- 

 nobiidce [Hynohius, Pachypalaminus) , and to a less ex- 

 tent in Dicamptodon. 



All these are theoretically primitive skull characters 

 of amphibians. Their appearance separately in diverse 

 forms is sufficient indication that the three families 

 Hynobiidce, Salamandridce, and Ambystomidcc, while con- 

 taining all the more primitive forms of the order, stand 

 in no direct genetic relationship to each other, but must 

 be derived from a more or less remote common stock 

 which combined the otic apparatus, lachrymal, and pre- 

 articular of Hynobius with the long maxilla, T-shaped 

 parasphenoid, and postfronto-squamosal arch of Tylo- 

 totriton. 



The evidence of Paleontology, as far as it goes, sup- 

 ports this view. I intend in a later paper to assemble the 

 meager facts regarding fossil salamanders. These facts, 

 it may be here stated, lend no support to the prevalent 

 view that the Proteida are an old, a primitive, or an an- 

 cestral group. 



The following outline classification indicates the size 

 and position of the modem groups. The genera and 



