138 University of Texas Bulletin 



TROCHUS LATICONICUS n. sp. 







PI. 10, figs. 30-31 



MEASUREMENTS : I II 



Height 9.0 7.8 



Greatest width 8.9 8.8 



Aperture, height 3.0 2.5 



Aperture, width 4.4 4.0 



HORIZON: Weno formation, shale facies. Has so far been found 

 only in the zone of Gervilliopsis invaginata (White) . 



TYPE LOCALITY: 601, pit of brickyard, one and three-fourths miles 

 southeast of Gainesville, Texas. 



DESCRIPTION: Shell small, conical, angulated. Volutions five of 

 which, two earliest in this type, are nearly smooth. Form trochoid, apical 

 angle 55 degrees, sutures impressed, ornamentation consists of a coarse, 

 revolving spiral on the keel, ten finer spirals above, the alternate ones 

 being coarser and consisting of equal low rounded tubercles, the others 

 being straight fine revolving elevated ridges ; and below the keel ten eqaul 

 similar non-tuberculate spiral ridges, each about half the width of the 

 intervening valley. Growth lines numerous, fine, sigmoid, oblique to the 

 ridges. Umbilicus concealed, small if any; aperture broken; probably 

 obliquely oval. The next tuberculate ridge above the keel is thicker than 

 the others and the keel and it lie just above the suture on the younger 

 whorls and form a distinct angulation at the base of each volution. The 

 shell on the last volution is thick (one half mm.) and the external markings 

 well preserved. 



Trochus sp. Shattuck 1 from the Buda limestone at Austin differs from 

 our species in having a larger apical angle (66 degrees) and straighter, 

 non-angulated sides. Trochus texamts Roemer 2 from the Barton Creek 

 (Austin, Texas) fauna of the Edwards limestone differs locally from our 

 species in the nature of the ornamentation, the straightness of the sides 

 and apparently in the shape of the aperture. This species is also described 

 as having a pointed tooth on the inner margin of the outer lip. 



iShattuck, U. S. G. S. Bull. 205, p. 31, pi. XIX, figs. 2-3. 

 2 Roemer, Pal. Abh., vol. 4, pt. 4, p. 15, pi. 1, fig. 13. 



