94 MESOZOIC AND CENOZOIC ECHINODEKMATA OF THE UNITED STATES. 



Holaster ungula Gabb, 1859, Cat. Invert. Fossils Cretaceous, p. 19. 

 Hemiaster ungula Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 77. 

 Hemiaster ungula Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 

 Hemiaster ungula Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 85, 86, PI. XLVI, figs. 2a-g. 

 Hemiaster ungula Johnson, 1905, Acad. Nat. Sci. Philadelphia Proc, vol. 57, p. 7. 



Hemiaster ungula Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 301-302, PL XVI, 

 figs. 5-11. 



Determinative characters. — -Test oval, cordiform, elevated; upper surface inflated, elevated 

 posteriorly; lower surface flat; sides sloping; anterior sulcus narrow and deep. Ambulacra 

 narrow; poriferous zones straight, depressed, petaloidal. Peripetalous fasciole deeply bent 

 inward between the anterior and posterior paired ambulacra. Apical system small, compact. 

 Peristome transversely oval near anterior margin. Periproct oval, supramarginal. 



Dimensions. — Length 31.25 millimeters; -width 28 millimeters; height 21.9 millimeters. 



Description. — This species has an oval, cordate test, that is very much elevated in the 

 posterior portion. Anteriorly the upper surface slopes rapidly, so that the margin is much 

 thinned down, losing the full round aspect of the previously described forms. The sharp ridge 

 on the posterior portion of the test is terminated by a nearly vertical truncation of the posterior 

 margin. The base is flat, save for the peristomial depression. 



The ambulacra are narrow. The poriferous zones are petaloidal, straight, and deeply 

 depressed on the upper surface. The unpaired ambulacrum is placed in the anterior sulcus and 

 but slightly exceeds the other areas in width. The petals of the anterolateral pair are twice 

 the length of the posterolateral. The pores of the paired ambulacra are elongated and sepa- 

 rated, those of the single ambulacrum small, oval, and approximated. 



The surface of the test is covered with small tubercles, between which are numerous minute 

 granules. The peripetalous fasciole is distinct and bent outward between the anterior and 

 posterior paired ambulacra. 



The apical system is small and situated posterior to the center of the upper surface. The 

 right anterolateral genital plate is very large and widely separates the posterior pair of oculars. 

 The posterolateral genitals have large perforations. 



The peristome is transversely oval, bilabiate, with a prominently projecting lower lip. 

 The periproct is large and is situated at the upper part of the truncated face of the posterior 

 margin. 



Related forms. — It is separated from H. parastatus, with which it is found, by the narrower 

 anterior groove, more central apical system, less inflated sides and sharper posterior keel. 



Localities. — Chesapeake & Delaware Canal (type), and Timber Creek and Vincentown, N. J. 



Geologic horizon. — Vincentown sand of Rancocas group, Upper Cretaceous. 



Collections. — Academy of Natural Sciences of Philadelphia (1503); American Museum of 

 Natural History, New York; Johns Hopkins University. 



Hemiaster texanus Roemer. 



Plate XLIX, figures la-j. 



Hemiaster texanus Roemer, 1849, Texas, p. 393. 



Hemiaster texanus Poemer, 1S52, Die Kreidebildungen von Texas, p. 85, PI. X, fig. 4. 



Hemiaster americanus Gabb, 1853, Naturwiss. Ver. in Halle Jahresb., pp. 372, 373. 



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



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



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



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



Hemiaster texanus Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 86, 87, PI. XL VII, figs. la-i. 



Hemiaster texanus Cragin, 1893, Geol. Survey Texas Fourth Ann. Kept., p. 155. 



Hemiaster texanus Aguilera, 1897, Inst. geol. Mexico Bol. Nos. 4, 5, 6, p. 215. 



Hemiaster texanus Hill and Vaughan, 1898, U. S. Geol. Survey Eighteenth Ann. Rept., pt. 2, PI. LXI, figs, la, lb. 



Hemiaster ? texanus Bose, 1899, Inst. geol. Mexico Bol. No. 3, p. 11. 



Hemiaster texanus Hill, 1902, U. S. Geol. Survey Twenty-first Ann. Rept., pt. 7, PI. XLV, fig. 5. 



