648 E. B. BRANSON 



less than 4 mm. wide and hounded on either side by a sharp crested 

 ridge runs toward the narrow end. The lateral edges are sharp. 

 Six to ten narrow grooves run parallel with the margins on each side 

 of the tooth, beginning 11 mm. from the outer end, extending out- 

 ward for 7 mm., and bifurcating and becoming obsolete in passing 

 outward. Next to the lateral margins close-set grooves that pass 

 backward and outward intersect the longitudinal grooves at an 

 angle of about 45 . The concave surface of the tooth is marked 

 with close-set longitudinal grooves formed by the etching of the 

 surface, and opening the longitudinal pores. 



Deltodus mercurii Newberry (PL V, Figs. 1-11 ; PI. II, Figs. 27 and 2S; PI. VI, 



Figs. 1-6) 

 1876. Deltodus mercurii Newberry, J. N. Macomb, Rcpt. Exp. Expcd. from 



Santa Fe, N.M., to the Junction of the Grand and Green Rivers of the 



Great Colorado of the West, p. 137, PI. 3, Figs. 1, ia. 

 1883. Deltodus powellii St. J. and W., Geol. Surv. III., Vol. VII, 154-56, 



PI. IX, Figs. ia-f. 

 1883. Deltodus mercurii St. J. and W., Geol. Surv. III., Vol. VII, PI. X, Figs. 



sa-d. 

 18S3. Deltodus propinquus St. J. and W., Geol. Surv. III., VII, 156-5S, PI. X, 



Figs. 4a-e (not Figs. 3a-e). 

 18S9. Deltodus mercurii, Deltodus powellii, and Deltodus propinquus A. S. 



Woodward, Catalogue of the Fossil Fishes in the British Museum, Part I, 



pp. 200-201. 



Newberry described Deltodus mercurii from one imperfect 

 specimen and St. John and Worthen described Deltodus propinquus 

 from three specimens. The following descriptions are based on a 

 large series, though only a few teeth are nearly perfect. Some 

 specimens from the Embar agree with the figures of D. powellii, 

 others in the same series agree with the mandibular teeth described 

 as D. propinquus, and others with D. mercurii. St. John and 

 Worthen suggested 1 that a large series might show these forms to 

 be conspeciric. 



The maxillary teeth are large, of medium width compared to the 

 length; the posterior margin is strongly arched, with an angle 

 between the outer and inner ends of the crown of about 147 ; the 

 anterior margin is almost straight. The inner end of the tooth is 



1 Op. cit., p. 158. 



