f^'-ARK] HEMI ASTER PARASTATUS. 83 



lacial furrows are shorter, and the anal opening; is diflerently situated 

 as i>reviously mentioned in the description of the hitter species. 



Locality and geological horizon. — Epiaiitcr Whitci is from the Washita 

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

 found in the Duck creek chalk of Denison, associated with Hamites 

 Frcmontii Marcou. 



Collection. — U. S. National Museum. 



flEMIASTER PARASTATUS (Morton). 



riate XLV, Figs. la-m. 



Spatatigus sp. Morton, 1830. Am. Jour. Sci., Ist ser., vol. 17, p. 286. 



SjHitanfius cor-marinum (?) Morton, 1830. Am. Jonr. Sci., 1st ser., v'ol. 18, p. 250, PI. 



3, Fig. 10. 

 Spatangus cor-marinum ( ? ) Morton, 1830. Philadelphia Acad. Nat. Sci. Jour., Ist ser. 



voi. 6, p. 199. 

 Sjxitaiigiis paranialHS Morton, 1833. Am. Jonr. Sci.. 1st ser., vol. 23, p. 294. 

 Spatauffiis parastatus Morton, 1834. Synopsis Organ. Remains, Cretaceous, p. 77, PI. 



3, Fig. 21. 

 Hemiasler parasUiliis Agassiz and Desor, 1847. Cat. rais., p. 141. 

 Hemiasler parastatus d'Orbigny, 1847. Prodrome, vol. 2, p. 270. 

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

 Hemiaster parastatus d'Orbigny, 1853-'56, Paleont. fran^aise, vol. 6, p. 265, PI. 894 



Fig. 4. 

 Hemiaster parastatus Desor, 1858. Synop. des fichinides fossiles, y>. 373. 

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

 Hemiastei- {^) parastatus Meek, 1864. Smith. Misc. Coll., a^oI. 7 (177), p. 3. 

 Hemiaster parastatus Clark, 1891. Johns Hopkins University Circulars, No. 87. p. 77. 



Determinative characters. — Test cordiform, inflated; upper surface 

 elevated, with deep groove on anterior surface and sharp ridge i)os- 

 teriorly that is terminated by the fl^t, nearly vertical, truncated face 

 of the posterior margin. Ambulacral petals depressed, the anterior 

 pair twice as long as the posterior. Apical disk small, compact. 

 Mouth opening with distinct, overhanging lip. Anal opening small, 

 situate<l high on truncated surface. 



Dintensions. — Length, 1^ inches; width, 1^ inches; height, 1| inches. 



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

 eordiform test, with deep anterior sulcus and high posterior ridge on 

 the n])per surface, the latter terminated by the high and nearly verti- 

 cally truncated face of the posterior margin. The sides are rounded 

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

 depression. 



The ambulacral areas are very unlike. The poriferous zones are 

 distinctly petaloidal (PI. xlv. Fig. le). The petals of the postero- 

 lateral i>air are short and broad. Those of the anterolateral ])air arc 

 bent backward at their center, depressed, and about twice the length 

 of the posterolateral pair. The pores are slightly elongated (PI. xlv, 

 Fig. 1/t). The unpaired ambulacrum is very broad, the poriferous 



