DUNN: AMPHIBIA CAUDATA. 449 



in the sea-turtles. One constantly finds references to the skull of 

 such an animal as Necturus as being very "low," meaning apparently 

 primitive. Actually, of course, the skull is simple compared to higher 

 types, but this is not by any means the same thing as primitive, for 

 primitive amphibians had a skull far more complex than any animal 

 now living. We seek in vain in Necturus for lachrymals, dermosupra- 

 occipitals, tabularia, supratemporals, intertemporals, jugals, quadrato- 

 jugals and others "too numerous to mention." But all these bones 

 were possessed by the primitive amphibians. In the same way the 

 fact that Cryptobranchus has larval gill-arches is no indication of its 

 primitive character. It is merely a case of arrested development. 



The case for the primitiveness of Necturus rests on its separate 

 opisthotic (paroccipital) and on the character of the pubis. The 

 case for the Cryptobranchidae is chiefly the separate prearticulars, 

 the large size, and the fact that a fossil is known. Even the bran- 

 chials, larval as they are, differ from normal larval branchials in 

 the absence of an epibranchial. 



At any rate the primitive amphibian skull is not a simple one and a 

 temporal roof, or the remains of a temporal roof, should be a character 

 of the most primitive living salamanders. 



In opposition to this view may be placed the two characters of 

 Necturus just alluded to, but the pelvis of Necturus is so different from 

 that of the Mutabilia that there may be little real affinity, and the. 

 paroccipital may yet be found to occur in the development of more 

 than one larval salamander. 



A greater difficulty in the way of this view is the fact that in other 

 characters the newt skull is not as primitive as several which lack 

 any trace of the arch. For instance, Ranodon, with separate lachry- 

 mals and prefrontals, and Salamandra with two premaxillaries. The 

 fact that the premaxillaries of the salamanders with the temporal 

 arch are fused is perhaps the greatest obstacle to their being regarded 

 as primitive, for there is no disputing the fact that to have the pre- 

 maxillaries separate is more primitive than to have them fused. But 

 separate premaxillaries are sometimes found, as in Geotriton, along 

 with such specialized characters as the complete absence of the 

 lachrymo-prefrontal bone. 



The newt vertebrae are opisthocoelous and the carpus and tarsus 

 are ossified, but it is probable that the cartilaginous carpus and tarsus 

 of many of the modern salamanders is due to arrested development 

 and there are forms known from the European Miocene which have 

 the opisthocoelous vertebrae. 



