CRETACEOUS ECHINODEKMATA. 93 



HEMI ASTER STELLA (Morton). 



Plate XLVIII, figures 2a-d. 



Spatangus stella Morton, 1830, Am. Jour. Sci., lstser., vol.18, p. 245, PI. Ill, fig. 11. 

 Spatangus Stella Morton, 1S30, Acad. Nat. Sci. Philadelphia Jour., lstser., vol. 6, p. 200. 

 Spatangus stella Morton, 1834, Synopsis Organic Remains Cretaceous, p. 78, PL III, fig. 18. 

 Hemiaster stella Agassiz and Desor, 1S47, Catalogue raisonne, p. 141. 

 Hemiaster stella Desor, 1858, Synopsis des echinides fossiles, p. 373. 

 Hemiaster stella Gabb, 1S59, Cat. Invert. Fossils Cretaceous, p. 19. 

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



Hemiaster wetherbyi De Loriol, 1887, Recueil zool. Suisse, vol. 4, pp. 391-394, PL XVII, figs. 5-8." 

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

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

 Hemiaster stella Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 84, 85, PL XLVI, figs. la-d. 

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



Hemiaster stella Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 300-301, PL XVI, 

 figs. 1-4. 



Determinative characters. —Test small, oval, inflated, rounded before, truncated behind; upper 

 surface elevated posteriorly, sloping anteriorly; anterior groove short, not reaching the ambitus. 

 Ambulacra straight, depressed above. Apical system excentric and posterior. Peristome 

 bilabiate and near the anterior border. Periproct small, high above posterior margin. Fas- 

 ciole distinct. 



Dimensions. — Length 25 millimeters; width 21.9 millimeters; height 15.6 millimeters. 



Description. — This form was originally described by Morton in 1830, later, in 1833, it was 

 considered by the same writer as the young of the species for which the name parastatus was then 

 proposed. H. incrassatus is only a large form of H. stella and Hemiaster wetherbyi is also appar- 

 ently identical with the same species. 



The test is small, oval, and cordate, and much elevated on the posterior portion of the upper 

 surface. The whole test has a rounded, full outline, that is much increased by the absence of 

 the usually deep anterior groove, which in H. stella does not reach the margin. The posterior 

 border is nearly vertically truncated. 



The ambulacra are depressed in the petaloidal portions which, in the anterolateral pair, 

 are twice as long as in the posterolateral. The poriferous zones are narrow; the pores have 

 transverse slitlike openings. The unpaired ambulacrum is situated in the anterior groove. 



The surface of the test is covered with innumerable small tubercles between which is a 

 microscopic granulation. The peripetalous fasciole is very distinct, oval, and passes with a 

 regular curve about the ends of the petaloidal areas. The surface of the test is covered with 

 minute tubercles, between which are microscopic granules. The apical system is small and is 

 situated posteriorly to the center of the upper surface of the test. 



The peristome is transversely oval, bilabiate, and placed near the anterior margin. The 

 periproct is small, oval, and is situated at the upper part of the truncated posterior margin. 



Related forms. — The shallow anterior groove which falls short of the margin and the full 

 elevated test readily distinguish it from other species. 



Localities. — -Gloucester (type), near Blackwoodstown (figured specimen), and Timber 

 Creek, N. J. 



Geologic 7tor£zo7i,.— Vincentown sand of Rancocas group, Upper Cretaceous. 



Collections. — U. S. National Museum (2208); Academy of Natural Sciences of Philadelphia; 

 Johns Hopkins University. 



Hemiaster ungula (Morton). 



Plate XLVIII, figures 3a-g. 



Spatangus sp. Morton, 1830, Am. Jour. Sci., 1st ser., vol. 17, p. 286. 

 Spatangus ungula Morton, 1833, Am. Jour. Sci., 1st ser., vol. 23, p. 131, PL X, fig. 6. 

 Spatangus ungula Morton, 1834, Synopsis Organic Remains Cretaceous, p. 78, PL X, fig. 6, 

 Micraster ungula Agassiz and Desor, 1847, Catalogue raisonne, p. 141. 

 Spatangus ungula Bronn, 1848, Index paheontologicus, vol. 1, p. 1161. 

 39800 °— 15 7 



