North American index fossils, invertebrates . 1923.) , orbicular, very much depressed, but swelling towards the middle, and depressed at apex; diameter 160 mm. X (Choptank) of Maryland. (Abundant.) 29. S. fairbanksi Merriam. than preceding (maximum diameter 36 mm.), broadest posteriorly; margin scarcely notched. Lower Miocenic (Vaqueros formation) of California. 592 NORTH AMERICAN INDEX FOSSILS. XX. EcHiNARACHNius from Scufella in its excentric apical system. Pliocenic-Recent. 30. E. gibbsi Remond. outline much li
North American index fossils, invertebrates . 1923.) , orbicular, very much depressed, but swelling towards the middle, and depressed at apex; diameter 160 mm. X (Choptank) of Maryland. (Abundant.) 29. S. fairbanksi Merriam. than preceding (maximum diameter 36 mm.), broadest posteriorly; margin scarcely notched. Lower Miocenic (Vaqueros formation) of California. 592 NORTH AMERICAN INDEX FOSSILS. XX. EcHiNARACHNius from Scufella in its excentric apical system. Pliocenic-Recent. 30. E. gibbsi Remond. outline much like Scutella fairhanksi, but larger, and apical system about one fourth the longitudinal diameter from the pos-terior end; ambulacra broad, the transverse grooves continuednearly to center; posterior petals flexuous; periproct of California. 31. E. interlineatus Stimpson. (Fig. 1924.) (ranging to over 120 mm. in diameter), pentagonal to circular; summit nearly central, in front of excentric apical system;.
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