Turritella from Buda and Georgetown Limestones 15* 

 Turritella georgetownensis, n. sp. 

 Plate IV, figures 1, 2 



Dimensions. Apical angle 15, sutural angle 3. 



Description. Shell tall, turreted, whorls seven or more 

 in number, suture well impressed, sides of whorls flat and 

 square-shouldered on the posterior side, height of whorl 

 about equal to the width. Ornamentation consists of five 

 nodular ribs, the posterior rib slightly larger than the 

 others. The ribs are far apart and the interspaces covered 

 with lines of growth. Between the two anterior ribs is 

 inserted a fine thread. The shell is not preserved well 

 enough to tell whether this thread is plain or beaded. 



Comparisons. Comparing our species with Roemer's 

 Turriiella seriatim-granula 1 a we find that the size of the 

 apical angle of Roemer's species is 12, while ours is 15, 

 and that the middle rib on the whorl of T. seriatim-granu- 

 lata is separated from the others by fine raised lines. Gabb 1 

 says that the ornamentation of T. seriatim-granulata va- 

 ries greatly and that the posterior and anterior margins of 

 the whorls are very slightly beveled. This condition does 

 not exist in our species which has square-shouldered whorls. 



In Turritella granulata, Sow., var. cenomanensis, D'Orb. 

 the whorls are slightly convex and have two bands that are 

 inclined toward the sutures. This gives the whorls a bev- 

 eled form, while in our species the whorls lack these bands 

 and are square-shouldered. Also in Turritella granulata, 

 Sow., var. cenomanensis, D'Orb. the height of the whorl in 

 proportion to the width is greater than in our species. 



Number of specimens. 1. 



Occurrence. Georgetown limestone, Shoal Creek, Austin, 

 Texas. 



Geological Survey of California, Vol. 1, p. 132. 



