84 University of Texas Bulletin 



The internal suture of a small individual whose form and ribbing mainly 

 agree with the last named individual is shown in figure 8. This suture 

 has six lateral and internal saddles and five lobes. The anti-siphonal lobe 

 is trifid, the remaining ones bifid. 



AT^ 



Fig. 8. Scaphites hilli Adkins and Winton, external and internal suture, camera 

 lucida drawing, x 10. 



Very closely related to this species is Scaphites worthensis Adkins and 

 Winton (Duck Creek marl) which, however, lacks the ventro-lateral tu- 

 bercle; its suture also differs in several respects. Scaphites semicostatus 

 Roemer and S. texanus Roemer, have been described from the Eagleford 

 formation near New Braunfels; S. vermiculus Shumard from the Eagle- 

 ford near Woodlake, Grayson County; and S. vermicosus Shumard from 

 the Navarro near Dresden, Navarro County. 



ENGONOCERAS SERPENTINUM (Cragin) 

 PI. 4, figs. 3, 5-6, 12 



1900: Sphenodiscus belviderensis, var. serpentinus Cragin, Colo. Coll. Stud., viii, p. 31, 



pi. 2, figs. 4-6. 

 1903: Engonoceras serpentinum Hyatt, U. S. G. S., Mon. XLIV, p. 162, pi. XIX, 



figs. 7-14; pi. XX, figs. 1-5. 

 1918: Engonoceras serpentinum Stephenson, U. S. G. S., Prof. Paper 120-H, p. 143. 



This distinctive Engonoceras is frequent in the shales of the Middle 

 Weno formation in Grayson and Cooke counties, Texas. Shell nacreous 

 in the material studied, with fine, close, sigmoid, radial striae; suture 

 simple, as figured by Hyatt (U. S. G. S., Mon. XLIV, pi. XIX, fig. 7) ; 

 venter rather square, angulated and rounded at edges, zigzag due to 

 alternating marginal tubercles on the two flanks. 



HORIZON: Lower and Middle Weno shale and ironstone; Pawpaw 

 shale. 



LOCALITIES : Frisco cut, three-fourths mile north of Union Station, 

 Denison, Texas, and the cut of Duck Creek just west of this locality; pit 

 of brickyard, one and three-fourths miles southeast of Gainesville, Texas ; 

 Pawpaw bluff on the Red River, northwest of Cedar Mills, Texas. 



