184 APPENDIX E. PALAEONTOLOGY. 



Occurs rather abundantly with the preceding species at Cross Timbers, 

 Texas. 



Ammonites — (undetermined.) 

 Paleontology, PI. — , fig. — . 



Several specimens of a small variety of ammonite, such as is repre- 

 sented in the figure, were found with the two last-described species, but 

 they are too imperfect for satisfactory description. 



ECHINODERMATA. 



Hemiaster elegans, Shumard. 

 Paleontology, PI. 2, fig. 4, a, b, c. 



Shell ovate orbicular, moderately convex at summit, broadly emargi- 

 nate anteriorly ; anal extremity truncated almost vertically, very slightly 

 excavated ; ambulacra sub-petalloid, broad, situated in shallow depres- 

 sions, antero-lateral areas widely divergent, extending to the margin of 

 the test, postero-lateral areas much less divergent and short, peripetalous 

 fasciole indistinct ; mouth transverse reniform, not far from the anterior 

 border, post oral tuberculated space lanceolate ; anus oval longitudinal, 

 sub anal fasciole scarcely visible; surface of test covered with small 

 spinigerous tubercles, with minute granulse in the interspaces. The 

 dimensions of the largest specimen that I have been permitted to ex- 

 amine are as follows: length, 2 7-10 inches; greatest width, 2 5-10 

 inches; height, 1 5-10 inch. 



This exceedingly elegant species occurs in great numbers in the cre- 

 taceous strata at Fort Washita. 



Holaster simplex, Shumard. 

 Paleontology, PI . 3, fig. 2. 



Shell ovate, sub-cordate, gibbous, regularly rounded superiorly, most 

 prominent near apex, which is sub-central, declining at first gently to- 

 wards the mouth, then abruptly, truncated posteriorly, with a thread-like 

 carina leading from the apex to the anus ; oral sinus shallow, rounded ; 



