Weno and Pawpaw Formations 93 



and narrower than the first lobe, and apparently is bifid; it lies at the 

 level of the dorso-marginai tubercles. The second lobe lies on the um- 

 bilical wall and is broad and flat, but from the material at hand its de- 

 tails can not be described. Between it and the tall narrow anti-siphonal 

 lobe there is a depressed saddle-like space. This description and figure 

 of sutures are taken from the individual figured on plate 1, figure 6. 



Fig. 12. Mortoniceras worthense n. sp., suture of individual, Plate 1, Figure 6, camera 

 lucida drawing, x 10. 



This species has similarities to Mortoniceras inflatum var. spinosum 

 Pervinquiere 1 (Vraconian of Tunis). One individual of five volutions 

 has two gaps in the ribbing of the last volution; they have no obvious 

 relation to the branching or doubling of ribs. The same feature is noted 

 in the earlier volutions in this species. 



ACANTHOCERAS WORTHENSE n. P . 



PI. 1, figs. 11-13, 16-17, 20-25 

 1920: Acanthoceras sp. Winton and Adkins, Univ. Texas Bull. 1931, p. 69. 



MEASUREMENTS : PI. 1, fig. 12 PI. 1, fig. 13 



Type (I) II 



Greatest diameter 14.9 mm. 13.8 



Height of last whorl 6.0 mm. 6.0 



Width of last whorl 6.0 mm. 5.0 



Width of umbilicus 1.4 mm.(?) 1.0 



HORIZON: Pawpaw formation, basal two-thirds, clay facies. 



LOCALITY: 723 (type locality), near Fort Worth, Texas; 714, 715, 

 716, 719, 724, near Fort Worth, Texas. The species is generally abundant 

 in favorably weathered exposures of the clay phase. 



DESCRIPTION: Shell discoidal, compressed, four or more volutions 

 considerably embracing, umbilicus consequently small ; shell keelless, sec- 



'Et. pal. tun., p. 229, pi. xi, fig. 3a-b. 



