86 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



Localities. — Fort Washita (type), Bexar County (figured specimen A), near Fort Worth, at 

 Preston, Grayson County (figured specimen B), on the Red River, near Austin, and near El Paso, 

 Tex. ; near Fort Washita, Okla. 



Geologic horizon. — Washita group of the Comanche series, Cretaceous. 



Collections. — U. S. National Museum (S3S2A); Geological Survey of Texas (B); Johns 

 Hopkins University. 



Family SPATANGIDiE. 



Genus ENALLASTER D'Orbigny. 



Enallaster texanus (Roemer). 



Plate XXXIX, figures 2a-g. 



To.mster texanus Roemer, 1849, Texas, p. 393. 



Toxaster texanus Roemer, 1852, Die Kreidebildungen von Texas, pp. S5, 86, PI. X, fig. 3. 



Toxaster ungula Giebel, 1853, Naturwiss. Ver. in Halle Jahresb., p. 373. 



Enallaster texanus D'Orbigny, 1853-60, Paleontologie francaise, vol. 6, p. 184, PI. DCCCL, figs. 1-7. 



Toxaster texanus Conrad, 1857, U. S. and Mex. Boundary Survey Rept., vol. 1, pt. 2, p. 145, PI. I, figs. 2a-e. 

 Enallaster texanus Desor, 1858, Synopsis des echinides fossiles, p. 358. 



Toxaster texanus Gabb, 1859, Cat. Invert. Fossils Cretaceous, p. 19. 



Toxaster texanus Meek, 1864, Smithsonian Misc. Coll., vol. 7 (177), p. 3. 



Enallaster texanus Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 77. 



Enallaster texanus Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 



Enallaster texanus Clark, U. S. Geol. Survey Bull. 97, pp. 78, 79, PI. XXXIX, figs. 2a-g. 



Enallaster inflatus Cragin, 1893, Geol. Survey Texas Fourth Ann. Rept., pp. 150, 151, PL XXIV, fig. 13. 



Enallaster texanus Cragin, 1893, Geol. Survey Texas Fourth Ann. Rept., p. 151. 



Enallaster texanus Cragin, 1894, Colorado Coll. Studies, vol. 5, p. 41. 



Enallaster inflatus Cragin, 1894, Colorado Coll. Studies, vol. 5, pp. 45, 47. 



Enallaster texanus Hill and Vaughan, 1898, U. S. Geol. Survey Eighteenth Ann. Rept., pt. 2, PI. LIII, figs. 4a-b. 



Enallaster texanus Hill, 1901, U. S. Geol. Survey Twenty-first Ann. Rept., pt. 7, p. 226, PL XXVII, figs. 4a-b. 



Enallaster sp. Hill, 1901, U. S. Geol. Survey Twenty-first Ann. Rept., pt. 7, p. 283. 



Determinative characters. — Test oblong, cordiform, broad in anterior portion, contracted 

 and truncated posteriorly, with deep anterior groove; upper surface convex, elevated; base flat, 

 depressed at the peristome; sides rounded; apex excentric and posterior. Ambulacra narrow 

 and unequal, the posterolateral pair much shorter than the others. Apical system small and 

 compact. Periproct situated high above the margin. 



Dimensions. — Length 16 to 45 millimeters; width 14 to 38 millimeters; height 9 to 27 

 millimeters. 



Description. — The test is oblong, cordiform, and elevated. The upper surface is convex, 

 with a well-defined anterior groove, narrow and slightly depressed at its head. On the posterior 

 face the surface is truncated to the margin. The sides are rounded and inflated. The base is 

 flat, except for the peristonal depression near the anterior margin and the central elevated region 

 extending from the same to the posterior border. 



The ambulacra are narrow and very unequal. The antero-lateral pair are large and curved 

 backward in their upper portions. The pores are very unequal ; those of the anterior zone are 

 small and near together, those of the posterior elongated, the outer nearly twice as large as the 

 inner series. There are about thirty-five pairs of pores in the petaloidal portion of each poriferous 

 zone. 



The postero-lateral pair are short and quite symmetrical in structure. There are sixteen 

 pairs of pores in the petaloidal portions of each poriferous zone. 



The anterior unpaired ambulacrum is situated in the anterior groove and is wider than the 

 other areas. An elongated pore appears in the external rows on alternate plates. On the inter- 

 vening plates the small rows are closely approximated. In the lower portion of each column the 

 plates are large and oblong. A pair of minute pores occupies the lower outer corner of each. 



The surface of the test is covered with a minute granulation, scattered among which are 

 numerous small tubercles. 



