North American index fossils, invertebrates . Fig. 1934. a-e, Hemiaster parastatus^ lower, lateral, upper and posterior views,X %> and adoral area enlarged ; f-h, H. texanus, lower, upper and lateral views,X %. (After Clark.) 48. H. parastatus (Morton). (Fig. 1934, a-^.) Cretacic. Upper surface elevated, with a deep anterior groove and a sharpposterior ridge, the latter truncated by the flat, nearly verticalposterior margin. Petaloid areas depressed, anterior pair bentbackward at their center and about twice the length of the pos-terior. Mouth opening with distinct overhanging lip. Anal ope
North American index fossils, invertebrates . Fig. 1934. a-e, Hemiaster parastatus^ lower, lateral, upper and posterior views,X %> and adoral area enlarged ; f-h, H. texanus, lower, upper and lateral views,X %. (After Clark.) 48. H. parastatus (Morton). (Fig. 1934, a-^.) Cretacic. Upper surface elevated, with a deep anterior groove and a sharpposterior ridge, the latter truncated by the flat, nearly verticalposterior margin. Petaloid areas depressed, anterior pair bentbackward at their center and about twice the length of the pos-terior. Mouth opening with distinct overhanging lip. Anal open-ing small, situated high on the truncated posterior surface. Ripleyan of Alabama and Mississippi; Jerseyan of New Jersey(Vincentown). ECHINODERMA TA—ECHINOIDEA. 601 XXXII. LiNTHiA heart-shaped, longer than broad; anterolateral ambulacradiffering from the posterolateral in shape and construction. An-terior ambulacrum in a deep groove, the pores round and small, in. Fig. 1935. Hemiaster lacunosus. «:, apical system, greatly enlarged (^, genitalplates ; m, madreporite ; r, radial plates) ; b^ portion of anterior petal where it joinsthe apical system, greatly enlarged; c, several plates of the right anterior petal, greatlyenlarged. (After A. W, Slocum.) pairs on either side. Anterolateral ambulacra longer and moredivergent than the others, with petals sunk in grooves. Poresunited by grooves. A peripetalous and lateral fasciole 49. L. variabilis Slocum. (Figs. 1911, 1936.) Cretacic. About half the size of L. tumidula, the posterior portion often
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