ECHINODERMATA. 299 



1833. Spatangus parastatus Mort., Am. Jour. Sci., ist ser., vol. 



23, P- 294- 



1834. Spatangus parastatus Mort. Synop. Org. Rem. Cret. Gr. 



U. S., p. 77, Pi- 3, fig. 21. 

 1853. Hemiaster parastatus Marcou, Explan. Text to Geol. 



Map U. S. and Brit. Prov. N. A., p. 47, pi. 7, fig. 8. 

 1855. Hemiaster parastatus d'Orb., Pal. Franc., Terr. Cret., 



vol. 6, p. 265, pi. 894, fig. 4. 

 1864. Hemiaster (?) parastatus Meek, Check List Inv. Foss. 



N. A., Cret. and Jur., p. 3. 

 1891. Hemiaster parastatus Clark, Johns Hopkins Univ. Circ., 



vol. 10, No. 87, p. 77. 

 1893. Hemiaster parastatus Clark, Johns Hopkins Univ. Circ., 



vol. 12, No. 103, p. 52. 

 1893. Hemiaster parastatus Clark, Bull. U. S. G. S., No. 97, 



p. 83, pi. 45, figs, i a-m. 

 1905. Hemiaster parastatus Johns., Proc. Acad. Nat. Sci. Phil., 



1905, p. 7. 



Description. Test distinctly cordate, the ventral surface flat 

 with the exception of the peristomal depression, the sides rounded 

 and inflated laterally and in front, the posterior side high and 

 nearly vertically truncated, the dorsal surface convex, greatly 

 elevated towards the posterior margin and with a distinct, deep, 

 anterior sulcus. Ambulacral areas dissimilar, petaloid, with the 

 petals depressed, those of the postero-lateral pair short and broad, 

 those of the antero-lateral pair curving forward and about twice 

 the length of the postero-lateral pair, the anterior, unpaired am- 

 bulacrum very broad, with the poriferous zones far apart and the 

 pores small and approximated. Interambulacral areas broad, 

 composed of large plates. Surface of all the plates covered with 

 small tubercles between which are numerous microscopic gran- 

 ules; the peripetalous fascicle broad and distinct. Apical disk 

 small, compact, posterior to the center of the dorsal surface but 

 in front of the apex of the test, the four genital plates distinctly 

 perforated and separated by the five small oculars. Oral opening 

 transversely arched, bilabiate, with a distinct, overhanging lip. 

 Anal opening small, situated high on the truncated posterior side. 



