14 
University of Texas Bulletin 
mented exteriorly with faint costae and thin lamellae; interior 
with fine, flat, wavy, radiating costae, separated by grooves of 
equal width. Superior valve convex, ornamented with many, 
irregular, wavy, radiating costae, eight of which are stronger 
than the others, and separated by three strong costae, often sup- 
plemented by weaker ones. The strong ribs sometimes bear 
lamellar spines, which, in the adult, are confined to the umbonal 
region. In the young specimens, all the ribs are spine bearing, 
and the spines extend throughout the length of the shell. Ears 
transversely ribbed. 
This species resembles S. hystrix Goldf., both in young and 
adult stages. However, there are eight heavy costas on this 
species, whereas S. hystrix has only six. 
Locality. — Shoal Creek, Austin, Texas. 
Spondylus texanus n. sp. 
PL II, figs. 1, 2, 3. 
Dimensions . — Length, 25mm.; breadth, 23mm. 
Description. — Shell small, subtrigonal, inequilateral, auricu- 
late; anterior straight; posterior slightly produced; base regu- 
larly rounded; surface marked by fifty or more fine, uneven, 
irregular, sometimes dichotomous costae, about equal in width to 
the grooves separating them. Ears ornamented with fine, ob- 
lique, pronounced striae; interior marked with costae, correspond- 
ing to those on the outside, strongest at base of shell, thereby 
giving it a crenulate-serrate appearance; muscle impression 
with a raised border in thickened portion of shell. Right valve 
unknown. 
Locality. — This and the above species were found in the 
chalky beds, about ten feet below the contact with the upper 
beds at Thirtieth Street, Shoal Creek, Austin, Texas. 
ANOMIIDAE 
Genus ANOMIA Muller. 
Anomia geniculata n. sp. 
PL II, figs. 4, 5. 
Dimensions. — Length, 10mm.; breadth, 11mm. 
Description. — Shell small, sub-ovate, acuminate; left valve 
