'20 fnicn'sity of Texas Bulletin. 



seems to range from near the base to the top. The material is 

 quite well preserved, but difficult to remove. 

 Locality. Shoal Creek, Austin, Texas. 



GASTEROPODA. 

 NATICIDAE. 



Genus TYLOSTOMA Sharpe. 



TYLOSTOMA HILLI n. sp. 

 PI. VIII, figs. 1, 2. PI. IX. 



Dimensions. Height about 100 mm.; maximum breadth, 

 77mm. ; minimum breadth, 52mm. 



Description. Shell large, globose, solid, greatly compressed; 

 spire elevated ; whorls five and one-half, convex ; body whorl 

 much larger than the others, inflated, about two-thirds the 

 height of the shell; surface smooth; varices well developed and 

 strong on the spire of the adult; aperture elongate; lip un- 

 known. 



Locality. Barton Creek, Shoal Creek, Austin, Texas. 



TYLOSTOMA HARRISI n. sp. 

 PI. X. figs. 12, 13, 14. 



Dimensions. Height, 39mm. ; breadth, 24mm. 



Description. Spire elevated, conical, whorls five, convex; su- 

 ture somewhat canaliculate; lip thin, slightly reflected; inner 

 lip callous; aperture acute posteriorly, rounded, produced an- 

 teriorly. Surface smooth, marked by fine lines of growth. The 

 varices are not prominent on the exterior of the type specimen. 

 They are, however, more pronounced on some individuals of 

 this species. They are well developed on casts. 



Locality. Shoal Creek, Barton Creek, Austin, Texas. 



CERITHIIDAE. 



Genus CERITHIUM Adanson. 

 CERITHIUM STANTONI n. sp. 



PI. X, figs. 1, 2. 

 Dimensions. Height, 32mm. ; breadth, 8mm. 



