78 BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



Type D. — Palatine series forming a parabolic arcb from one extremity 

 to the other, extending in advance of the uares. Three specimens, 

 two of them of full but not large size; one of the former fully double 

 the size of others from the same locality (the Platte Valley), which are 

 referred to types and B, with larval tongue and branchial stumps. 

 The others (4066), with larval tongue, but the branchise absorbed. 



Here may be mentioned a remarkable specimen (3982), which is in all 

 other respects fully developed, where the larval arch of teeth remains, 

 but has become open and slightly transverse, extending but little be- 

 yond the anterior margin of the nares. It is intermediate between 

 types D and A, and is the result of a retardation in development of the 

 larval arch, while type B is produced by a retardation by the preserva- 

 tion of the oblique lateral series of the larva at the expense of the arch. 

 I add here a description of the var. obscurum {Amblystoma ohscurum 

 Baird, Proceeds. Acad. Phila., 1869, p. 192). 



The head is very broad and the gape unusually large. The internal 

 nostrils are very large, their width half the diameter of the eye ; the 

 distance between their inner borders is the same as that between the 

 outer. The tongue is large, broader than long, its width about two- 

 thirds that of the upper jaw. 



The palatine teeth are in four series, collectively forming a broad in- 

 verted Vl ^^^ angles anterior, and would be quite sharp but that there 

 is an interruption along the median line. The branches reach as far 

 forward as the anterior border of the inner nostrils. They are decidedly 

 concave antero-externally. The ten inner anterior sections of the pal- 

 atine series are each about twice the length of the external ones; they 

 fall short of the inner border of the inner nares by nearly a diameter of 

 the latter, which space separates them from the outer section, which, 

 immediately behind the inner nares, are about as long as the latter are 

 wide, and do not pass exterior to their outer border. 



There are twelve costal furrows. The tail is compressed, but not 

 high. 



The color appears to have been of a uniform brown above and on the 

 sides, brownish yellow beneath. On the sides darker vertical blotches 

 can be detected in the single specimen before Die. Similarly indistinct 

 markings are visible on the tail. 



The very convex frontal region and the concave interrupted scries of 

 teeth alone distinguish this variety from the A. tigrinum of the West. 

 It differs from A. tigrinum of the East in much larger inner nares 

 and more widely separated nostrils, the inner borders of the two being 

 at about the same distance, instead of having the latter more approxi- 

 mated. The tongue is wider, as w(ill as the heal. The teeth are more 

 V-shaped and reach farther forward. The outliue of the limbs of the V 

 is concave antero-externally and is interrupted by spaces equal to the 

 wide nostrils, the outer section not extending beyond the nostrils. 



The specimen which represents this variety is from Fort Des Moines, 

 Iowa (i^o. 3994.) 



