North American index fossils, invertebrates . Fig. 1930. Cassidulus aquoreus. a, diagram showing arrangement of plates intoa floscelle around the peristome ; b, apical disc, much enlarged ; <r, several plates ofpetaloid region of anterior ambulacrum, much enlarged ; d, anterior ambulacrum en-larged ; <?, several plates of same, of oral region, much enlarged. (After W. B. Clark.) XXVI. EcHiNOCORYS Breyn. (Ananchytes Mercati.)Test large, oval in marginal outline, high. Upper surfacerounded or keeled. Lower surface flat. Ambulacra with but two ECHINODERMA TA—ECHINOIDEA. 597 pairs of pores w
North American index fossils, invertebrates . Fig. 1930. Cassidulus aquoreus. a, diagram showing arrangement of plates intoa floscelle around the peristome ; b, apical disc, much enlarged ; <r, several plates ofpetaloid region of anterior ambulacrum, much enlarged ; d, anterior ambulacrum en-larged ; <?, several plates of same, of oral region, much enlarged. (After W. B. Clark.) XXVI. EcHiNOCORYS Breyn. (Ananchytes Mercati.)Test large, oval in marginal outline, high. Upper surfacerounded or keeled. Lower surface flat. Ambulacra with but two ECHINODERMA TA—ECHINOIDEA. 597 pairs of pores which are best developed toward the center of theupper surface. Posterior ambulacra long and broad, with obliquepores. Peristome transversely oval; periproct oval, beneath theposterior margin; apical system elongate. Fig. 1931, a-d, Echinocorys ovalis, dorsal, posterior and ventral views, X Viyand enlargement of apical system ; e-hy Cardiaster cincius, dorsal, ventral and lateralviews, X %?> ^^^ enlargement of ambulacral plate. (After Clark.) 40. E. ovalis Clark. (Fig. 1931,0-0?.) contracted posteriorly; peristome near anterior margin; periproct situated on a slight (Vincentown) of New Jersey. XXVII. HoLASTER oval in marginal outline, flat beneath, swollen and highabove. Plates large. Anterior ambulacrum in a shallow opening subanterior, elliptical, broadest transversely. Analopening situated above the lower posterior margin, oval. Apicalsystem elongate. Comanchic to Tertiary. 41. H. completus Cragin. small, subcylindrical on a rotund ovate to broadly oval base; sides subvertical btit slightly convex; summit flattish-convex;unpaired ambulacrum about as conspicuous as the others; madre-poric function shared by four gen
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Keywords: ., bookcentury1900, bookdecade1900, bookidn, booksubjectpaleontology
