20 
University 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. PL IX. 
Dimensions — Height about 100mm.; 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. 
PL 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 anteriorly. 
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 spe- 
cies. They are well developed on casts. 
Locality. — Shoal Creek, Barton Creek, Austin, Texas. 
CERITHIIDAE 
Genus CERITHIUM Adanson. 
Cerithium stantoni n. sp. 
PL X, figs. 1, 2. 
Dimensions. — Height, 32mm.; breadth, 8mm. 
