Turritella from Buda and Georgetown Limestones 13 



margin of the whorl has two prominent nodular threads in 

 front of it, the anterior of these being the larger. The 

 other two ribs are near the posterior side of the whorl. The 

 middle rib is the most prominent. Between the anterior 

 rib and the middle one are two prominent nodular threads 

 plus finer threads. There is a fine line between the two 

 posterior ribs and two lines behind them. In addition to 

 this ornamentation the whorl is covered with fine lines of 

 growth. 



Turritella knikeri is distinguished from T. moorei by the 

 size of the angles and by the ornamentation. In Turritella 

 moorei the suture is well marked and the anterior margin 

 of the whorl is marked by an inclined striated band which 

 does not appear in Turriiella knikeri. In Turritella knikeri 

 the height of the whorls in comparison with the width is 

 greater than in Turritella moorei. In T. knikeri the suture 

 is not well defined. 



Number of specimens. 2. 



Occurrence. Buda limestone, Austin. 



Turritella shippi, n. sp. 

 Plate III, figures 1, 2 



Dimensions. Apical angle 81/2, sutural angle 10. 



Description. Shell small, elongated, sides of whorls 

 straight, whorls five or more in number, suture well im- 

 pressed at the bottom of a well defined channel. Ornamen- 

 tation consists of six ribs arranged in the following order 

 from the anterior side of the whorl : two elevated nodular 

 ribs with an intermediate nodular thread which gives an 

 impression of an elevated band on the whorl. On the an- 

 terior edge of this band is a nodular thread bordering the 

 channel in which the suture is impressed. Behind the an- 

 terior pair of ribs there is a space covered with lines of 

 growth. This is followed by two smaller nodular ribs close 

 together. Following these there is another striated space 

 in front of two large elevated nodular ribs the first of 



