12 University of Texas Bulletin 



Turritella manchacensis, n. sp. 

 Plate III, figures. 3, "4 



Dimensions. Apical angle 25, sutural angle 9. 



Description. Shell small, stout, body whorl unknown, 

 whorls slightly convex, suture well marked, height of the 

 whorl half the width, surface of whorl marked with five 

 square nodular ribs. The space between the posterior rib 

 and the preceding one is equal to the width of the latter. 

 The space between the other ribs is less than the width of 

 a rib. The anterior rib is the largest, the one behind it is 

 the smallest. The posterior rib is slightly smaller than 

 the two preceding it. In front of the anterior rib are two 

 fine plain threads. Fine striations are found between the 

 ribs. 



Comparisons. This differs from Turritella budaensis, 

 Shattuck, in having five ribs instead of four. In T. buda- 

 ensis the two middle ribs are the most prominent, whereas 

 in this species the anterior rib is the most prominent; in 

 T. budaensis the ribs are far apart, but in our species the 

 ribs are close together. In T. budaensis the apical angle 

 is four degrees smaller than in our species. 



Number of specimens. 1. 



Occurrence. Lower beds 1 of Buda limestone, first creek 

 south of Manchaca, Texas. 



Turritella knikeri, n. sp. 

 Plate III, figures 5, 6 



Measurements. Apical angle 7, sutural angle 9. 



Description. Shell is small, elongated, whorls seven or 

 more in number, whorls high, sides of whorls flat, aperture 

 unknown, sutures poorly defined. Ornamentation consists 

 of three prominent nodular ribs. The rib on the anterior 



lU In the vicinity of Austin the Buda Limestone displays two dis- 

 tinct phases : a lower, chalky, or marly, soft white rock, and an upper, 

 hard, yellowish to reddish rock." Whitney. 



