ciARK.l EPIASTER ELEGANS. 81 



Toxaster elcgans Meek, 1864. Smith. Misc. Coll., vol. 7 (177), p. 3. 



Macraster texanux Koemor, 1888. Neues Jahibuch fiir Min., Geol., u. Pal., Bd. i' pp. 



191-195, PL 6, Figs. 1-4. 

 Epiaster elcgans Clark, 1891. Jolins Hopkins University Circnlars, No. 87, p. 77. 



Determinative characters. — Test large, oblouj;-, cordiforni, flattened 

 both above and below ; sides rounded, with a shallow anterior groove 

 and truncated posterior margin. Ambulacra subpetaloidal, depressed ; 

 poriferous zones straight, pores with elongated, slit-like openings. 

 Apical disk small, compact. Mouth opening transversely oval, situated 

 near the anterior margin. Anal opening oval, situated on the truncated 

 posterior margin. 



Dimensions. — Length, i inches; width, 3f inches; height, 2 inches. 



Description. — Koemer in 1888 established a new genus and species 

 (Macraster texanus) for a form that is identical with Hemiaster elegans 

 described by Shumard in 1853. The species properly belongs to the 

 genus Epiaster. There does not seem to bo a sufficiently wide differ- 

 ence between the characters assigned to Macraster and those properly 

 belonging to Epiaster to Avarrant the acceptance of the former genus 

 for the present species. 



The test is very large and flattened on both the upper and lower sur- 

 faces. The sides are round. The groove on the anterior face is shallow 

 and cuts the margin lightly. The posterior face is obliquely but not 

 broadly truncated. 



The ambulacra! areas are nearly equal, depressed, with a distinct 

 furrow on the upper surface (PI. XLi, Fig. la). The poriferous zones 

 are long, wide, and straight, and the pores consist of slit like oj)euings 

 (PI. XLiii, Figs. 16, Id). The zones are subpetaloidal on the upper sur- 

 face, reaching quite to the upper margin of the rounded sides. The 

 unpaired ambulacrum is narrower than the others; the pores are smaller 

 and more closely approximated. 



The surface of both areas is covered with minute tubercles, between 

 which are microscopic granules (PI. XLiii, Fig. Id). 



The apical disk is small, compact, and consists of four large perfo- 

 rated genital plates and five small oculars (PL xliii, Fig. le). 



The mouth opening is transversely oval and situated near the anterior 

 margin (PI. XLii, Fig. la). 



The anal opening is large, oval, and situated on the truncated face of 

 the i)osterior margin (PI. xlii. Fig. lb). 



Related forms. — Epiaster elegans is most nearly related to E. Whitei, 

 the single other American representative of this genus, but is separated 

 from it by its great size, its excessively long subpetaloidal areas, and 

 the position of the anal opening, which is on an obliquely truncated sur- 

 face that opens downward, while on E. Whitei it is situated on a vertical 

 face that oi)ens ujiwards. 



Locality and geological horizon. — Epiaster elegans is from the Washita 

 formation of the Comanche series (lower Cretaceous) of Texas. It is 

 Bull. 97 6 



