1 8 Bulletin 26 102 



the elongate pores to the rounded pores of the paired ambulacral 

 areas. In E. texanus this ratio is four rounded pores to six elongate 

 ones, whereas in E. bravoensis it is five to seven. 



Number of specimens: 5. 



Occurrence: Buda Limestone, Austin, Round Rock, and 

 Manchaca, Texas. 



Genus Hemiaster, Desor 



Hemiaster calvini Clark 

 Plate VIII, figures 4-7; Plate IX, figures 1-3 

 Hemiaster calvini Clark, 1893, Johns Hopkins Univ. Cir., Vol. 12, No. 103, 



P- 52- 

 Hemiaster calvini Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 90, 91, 



PI. XLIX, figs. 2a-i. 

 Hemiaster calvini Bose, 1910, Instituto Geol. de Mexico Boletin 25, 

 p. 175, Lam. 43, figs. 3-5, 8; Lam. 44, figs. 1-8, Lam. 45, figs. 1-3, 5. 

 Hemiaster calvini Clark, 1915, XL S. Geol. Survey Monograph, Vol. LIV, 



p. 91, PI. XLVII, figs. 2a-i. 

 Dimensions. — Length, 31 mm.; width, 27.5 mm.; height, 

 22.00 mm. 



Description. — Test of medium size, slightly polygonal in 

 outline ; upper surface elevated ; lower surface flattened or slightly 

 swollen in the region of the plastron; posterior truncated; am- 

 bulacra moderately and about equally depressed on the upper 

 surface. 



The unpaired ambulacrum is situated in a relatively broad 

 and moderately deep groove beginning at the apex and extending 

 forward to the ambitus which it notches slightly in passing around 

 to the peristome. The pore zones are composed of pairs of small, 

 oval, or nearly rounded, obliquely set pores. The pores of each 

 pair are separated by a granule. This arrangement prevails 

 half the distance from the beginning of the ambulacrum to the 

 ambitus. Beyond this the pores are not so conspicuous, and con- 

 tinue to the peristome in widely separated pairs which are decidedly 

 oblique. 



The paired anterior ambulacral areas are broad, lanceolate, 

 and situated in deep grooves. The pore zones are broad at 

 their centres, but constricted at their ends. The pores of the 



