14 University of Texas Bulletin. 



mented exteriorly with faint costae and thin lamellae; interior 

 with fine, flat, wavy, radiating costse, 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. kystrix Goldl, both in young and 

 adult stages. However, there are eight heavy costae 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 costaa, 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 Miiller. 



ANOMIA GENICULATA n. sp. 



PI. II, figs. 4, 5. 



Dimensions. Length, 10mm.; breadth, llmm. 



Description. Shell small, sub-ovate, acuminate; left valve 



