106 University of Texas Bulletin 



from Hemiaster calvini and others by the absence of a conspicuous tubercle 

 between the pores of a pair in the unpaired ambulacrum and usually by 

 the larger size, the slighter depression of the ambulacral grooves, and the 

 shape of the test. It is stated that Hemiaster has peripetalous fascicles 

 while Epiaster lacks them ; but this character is of no value in the usual 

 Texas material, which entirely lacks fascicles. Hemiaster elegans and 

 Epiaster aguilerae are of large size, while Hemiaster whitei and Epiaster 

 wenoensis are of medium and small size. 



Test: Inflated, rotund, smooth, ambulacra nearly straight, only slightly 

 depressed. Widest point of test just anterior of apical system, tallest 

 point on mid-line posterior to apical system and one-third the distance 

 from it to the ambitus. Sides inflated, rather straight, greatest peri- 

 meter at bottom. Aboral side nearly flat, peristome region excavated, 

 with a projecting keel on the posterior lip and the grooves of the antero- 

 laterals and the anterior sulcus slanting into the peristome. Posteriorly 

 on the oral mid-line the test is inflated, the most prominent point being 

 near the posterior end of the test. Ambitus rounded, with only an antero- 

 lateral angulation just back of the point where the antero-lateral ambul- 

 acra cross the ambitus; posteriorly the test has a rounded outline. Test 

 narrowed to a pointed, very narrowly truncate posterior end. 



Unpaired ambulacrum lies in the shallow anterior sulcus, which is sim- 

 ilar in form to the other ambulacral grooves, but slightly narrower. Each 

 one has about thirty-one pairs of short slit-like pores set at a slight angle 

 to each other. 



Antero-lateral ambulacra diverge at an angle of about 150 degrees, 

 then turn forwards slightly, being thereafter almost straight to the am- 

 bitus. Pore zones similar, with the pores almost equal. Each zone has 

 about fifty pore pairs, the pores being short, slit-like, and not set at an 

 angle to each other. Both pores of the anterior zone and the anterior 

 pores of the posterior zone are equal ; the posterior pores of the posterior 

 zone are about one and one-third times as long. 



Postero-lateral ambulacra long, straight, diverge at an angle of about 

 60 degrees. About fifty-four pore pairs in each zone, pores slit-like, sim- 

 ilar and nearly equal, the interior ones being, however, shorter than the 

 exterior ones. 



Peristomal ambulacral pores. The ambulacra after crossing the am- 

 bitus continue as smooth finely granulated strips of large plates with 

 reduced pores, and end at the peristome. However, on approaching the 

 peristome the pores become conspicuous and are borne on elevated knobs 

 with a crater-like opening to one side of the top. These are present in 

 the following Texas species examined : Epiaster wenoensis n. sp. (most 



