124 University of Texas Bulletin 



"OCCURRENCE : On slope of Pawpaw Creek,'east of Denison, Texas, 

 in red ochraceous shell-conglomerate of the Pawpaw clays. The associate 

 fossils are Ostrea quadriplicata, Tapes dentonensis, Yoldia microdonta 

 Turritella seriatim-granulata, Sphenodiscus, Turrilites, etc." 



Although Cragin's description is very brief and general, it fits a common 

 Weno species of Pecten in many respects; the locality also makes it prob- 

 able that our Gainesville and Denison material is to be referred to Cragin's 

 species. 1 



HORIZON: Ironstone and shale facies, upper two-thirds of the Weno 

 formation. Basal Pawpaw formation, sand-ironstone facies. Very rare 

 south of the Red River region. 



"LOCALITY: Cut of St. Louis and San Francisco Railway, one mile 

 north of Denison, Texas (PI. 11, fig. 1) and pit of brickyards, one and 

 three-fourths miles east of Gainesville, Texas. Numerous localities in 

 Cooke and Grayson counties, Texas. In the pit of the Gainesville brick- 

 yard there are extensive sheets of nacreous shells consisting largely of 

 Pecten inconspicuus, Gervilliopsis invaginata and prodissoconchs and later 

 embryonic stages of Gryphea washitaensis. 



DESCRIPTION : Shell slightly elevated, smooth, jnequivalve, inequi- 

 lateral ; ventral margin almost the. arc of a circle whose diameter is the 

 antero-posterior dimension of the shell. Antero-dorsal margin almost 

 straight, postero-dorsal margin slightly concave near middle and more 

 elevated by a sharp fold above the ear than the antero-dorsal margin 

 the two make an angle of about 95 degrees at the umbo, the angle being 

 pointed and very slightly rounded at the tip ; the angle made by lines drawn 

 from the extremities of the two margins to the umbo is about a right 

 angle. The umbo projects slightly over the hinge line. Anterior and 

 posterior ears triangular, the latter having a longer base along the margin 

 than the former, and having nearly twice the area. Hinge line straight, 

 making an angle of about 46 degrees with the antero-dorsal margin and 

 an angle of about 42 degrees with the postero-dorsal margin. The term- 

 inal angle of the anterior ear is about 95 degrees; of the posterior ear, 

 about 100 degrees. The latter angle is broadly rounded. 



The ears have fine parallel sigmoid growth line which bend toward the 

 umbo at the hinge line, but at the dorsal margin bend anteriorly and 

 posteriorly and after ascending these margins, course concentrically across 



'This species has never been figured, so far as I can discover; the type is presumably 

 in the Colorado College museum, but efforts to get information about it have been 

 misspent. 



