North American index fossils, invertebrates . xanus, upper, lower, lateral and posterior views, X %• (AfterClark.) wide space. The anterior ambulacrum lies in a shallow groove;pores oblique and in pairs on either side. The anterolateral ambu-lacra diverge, are dorsally sunken, petaloid, and much longer thanthe posterolateral. Pores of the petaloid portion united, the outerones usually the largest. A fasciole present near the edge of thetest, surrounding the petaloid parts. Cretacic-Recent. 6oo NORTH AMERICAN INDEX FOSSILS. 46. H. texanus Roemer. (Fig. 1934,/-/^.) groove broad
North American index fossils, invertebrates . xanus, upper, lower, lateral and posterior views, X %• (AfterClark.) wide space. The anterior ambulacrum lies in a shallow groove;pores oblique and in pairs on either side. The anterolateral ambu-lacra diverge, are dorsally sunken, petaloid, and much longer thanthe posterolateral. Pores of the petaloid portion united, the outerones usually the largest. A fasciole present near the edge of thetest, surrounding the petaloid parts. Cretacic-Recent. 6oo NORTH AMERICAN INDEX FOSSILS. 46. H. texanus Roemer. (Fig. 1934,/-/^.) groove broad and deep. Anterolateral ambulacra bent backward in upper portion. Mouth opening large, transverselyoval. Anal opening large, oval, at center of truncated posteriorsurface. Characteristic of the Austin (Niobrara) of Texas. 47. H. lacunosus Slocum. (Fig. 1935.) from H. parastatus in its smaller size and in the pres-ence of sunken areoles around the tubercles; posterior interambu-lacral area rounded. Ripleyan of 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
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