92 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



Hemiastee parastatus (Morton). 

 Plate XL VIII, figures la-n. 



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



Spatangus cor-marinum (?) Morton, 1830, Am. Jour. Sci., 1st ser., vol. IS, p. 250, PI. Ill, fig. 10. 



Spatangus cor-marinum (?) Morton, 1830, Acad. Nat. Sci. Philadelphia Jour., 1st ser., vol. 6, p. 199. 



Spatangus parastatus Morton, 1833, Am. Jour. Sci., 1st ser., vol. 23, p. 294. 



Spatangus parastatus Morton, 1834, Synopsis Organic Remains Cretaceous, p. 77, PI. Ill, fig. 21. 



Hemiaster parastatus Agassiz and Desor, 1847, Catalogue raisonne, p. 141. 



Hemiaster parastatus D'Orbigny, 1847, Prodrome, vol. 2, p. 270. 



Spatangus parastatus Bronn, 1848, Index palseontologicus, vol. 1, p. 1160. 



Hemiaster parastatus D'Orbigny, 1853-1856, Paleontologie francaise, vol. 6, p. 265, PI. DCCCXCIV, fig. 4. 



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



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



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



Hemiaster parastatus Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, pi. 77. 



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



Hemiaster parastatus Clark, 1893, U. S. Geol. Survey Bull. 97, pp. S3, 84, PL XLV, figs. la-m. 



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



Hemiaster parastatus Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 298-300, PL XV. 



Hemiaster parastatus Slocum, 1909, Field Mus. Nat. Hist. Pub. 134, Geol. ser., vol. 4, No. 1, pp. 9, 10. 



Determinative characters. — Test cordiform, inflated ; upper surf ace elevated, with deep groove 

 on anterior surface and sharp ridge posteriorly that is terminated by the flat, nearly vertical, 

 truncated face of the posterior margin. Ambulacral petals depressed, the anterior pair twice as 

 long as the posterior. Apical system small, compact. Peristome with distinct, overhanging 

 lip. Periproct small, situated high on truncated surface. 



Dimensions. — Length 37.5 millimeters; width 37.5 millimeters; height 28.12 millimeters. 

 Description. — This interesting and rather common form has a high, cordiform test, with 

 deep anterior sulcus and high posterior ridge on the upper surface, the latter terminated by the 

 high and nearly vertically truncated face of the posterior margin. The sides are rounded and 

 inflated. The base is flat, with the exception of the peristomial depression. 



The ambulacra are very unlike. The poriferous zones are distinctly petaloidal. The petals 

 of the posterolateral pair are short and broad. Those of the anterolateral pair are bent back- 

 ward at their center, depressed, and about twice the length of the posterolateral pair. The pores 

 are slightly elongated. The unpaired ambulacrum is very broad, the poriferous zones far apart, 

 and the pores small and approximated. 



The surface is covered with small tubercles, between which are numerous microscopic 

 granules. 



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

 four genital plates are distinctly perforated and separated by the five small oculars. 



The peristome is transversely arched and bilabiate. The lower lip projects prominently. 

 The periproct is small and situated high on the truncated surface of the posterior margin. The 

 peripetalous fasciole is broad and distinct. 



Related forms. — H. parastatus is most closely related to H. ungula, from which, however, it is 

 separated by its deeper and broader anterior sulcus, more posterior position of the apical system 

 and more inflated sides. It is apparently distinct from all of the many species described from 

 European deposits. 



Localities. — Gloucester County (type), Timber Creek, and Vincentown (figured specimen), 

 N. J.; Pontotoc, Ala. (Slocum). 



Geologic horizon. — Vincentown sand of Kancocas group, New Jersey, and Kipley formation, 

 Alabama; Upper Cretaceous. 



Collections. — Academy of Natural Sciences of Philadelphia (1487); American Museum of 

 Natural History, New York; Johns Hopkins University. 



