Weno and Pawpaw Formations 137 



shell is incurved to form a rostrum-like constriction. There are 8 to 15 

 roughly concentric, sharply elevated ridges which contract towards the 

 posterior end of the shell. 



The species is occasional in the lower Weno marl of the Fort Worth 

 region, especially at locality 618, in association with Pecten georgetown- 

 ensis, Ancycloceras bendirei. Schloenbachia wintoni, Turritella worthensis, 

 and Venericardia wenoensis. 



GASTROPODA 



AMBERLEYA GRAYSONENSIS n. sp. 



PI. 6, fig. 5 



MEASUREMENTS : ( Type individual ) . 



Height 21.0 mm. 



Breadth (estimated) 17.2 mm. 



Last whorl, height 11.0 mm*. 



Last whorl, breadth 10.0 mm. 



HORIZON: Basal stratum of Weno shale, in association with Ostrea 

 quadriplicata, Gryphea washitaensis, Salenia sp. and various echinoids. 



LOCALITY: 606, just south of Frisco track, two and one-half miles 

 north of Denison, Texas. 



DESCRIPTION : Shell conical, turreted, spiral angle about 63 degrees 

 (estimated, shell of type distorted) ; volutions three or more, the terminal 

 one being over one and one-half times the diameter of the next smaller one. 

 Volutions angular, projecting, cross-section somewhat pentagonal. The 

 volutions bear externally three coarse revolving ridges, of which the outer 

 ones form the upper and lower shoulders of the volution. These ridges 

 are equal and equally spaced, the distance between them being about two 

 times the width of a ridge. The volution is crossed transversely by lan- 

 ellar growth lines with thin overlapping irregular edges. From the center 

 of the spire these trend sharply forwards, and crossing the first heavy ridge 

 then pass obliquely across the outer face of the volution and after travers- 

 ing the marginal strip of the volution on the other side of the ridges, dis- 

 appear at the suture. They form slightly elevated imbricated low nodes 

 on crossing the three spirals. Umbilicus absent, aperture indeterminate. 



