MIOCENE ECHINODERMATA. 207 



Determinative characters. — Test small to large in size, suboval to subovate in marginal 

 outline; truncated or convex posteriorly; shallow notches opposite the anterior petals, deep 

 ones opposite the posterior pair; one large lunule in the posterior interambulacrum; margin 

 thick; much depressed, being low and nearly flat along the front and sides, but rising toward 

 the center and posteriorly in a low longitudinally elongate mound. Apex slightly excentric 

 posteriorly, under surface flat. Ambulacral petals large, the posterior pair longer than the 

 rest and curved around the lunule. Apical system excentric anteriorly. Peristome small, 

 subcircular, excentric anteriorly; ambulacral furrows simple and straight for a short distance 

 from the peristome, then forking. Periproct very small, subelhptical, at the edge of the lunule 

 nearest the peristome. 



Dimensions. — Specimen A: Length 97 millimeters; width 79 millimeters; height IS milli- 

 meters. Specimen B: Length 62 millimeters; width 58 millimeters; height 11 millimeters. 

 Specimen C: Length 31 millimeters; width 28 millimeters; height .5 millimeters. 



Description. — This handsome species, the only representative of the genus Encope yet reported 

 from the Cenozoic deposits of the Atlantic coast, was described by Ravenel as early as 1842. At 

 first he placed it in the genus Scutella, but a few years later assigned it to the genus Encope. 

 Both Liitken and Conrad founded new genera upon this species, but there appears to be no good 

 ground for the recognition of either. Conrad's new species, Macrophora raveneli, is believed 

 to have been merely a young specimen of Ravenel's species. This species is rather abundant 

 in a few localities in South Carolina and Florida, but is rare elsewhere. The test is variable in 

 size, ranging from less than an inch to nearly 4 inches in longitudinal diameter. In marginal 

 outhne it is either suboval, somewhat ovate or obovate, or subquadrate; usually broader near 

 the posterior end than near the anterior end; posterior border usuaDy truncated, sometimes 

 convex; a shallow notch opposite the odd petal, slightly deeper rounded ones opposite the 

 anterior paired petals, and large deep angular ones opposite the posterior petals; the posterior 

 notches vary from a flaring and subrectangular form in small specimens to a less open and more 

 acute form, or one with parallel sides in larger specimens. A large lunule occupies the larger 

 part of the posterior interambulacrum, which varies in form from circular in very small speci- 

 mens to oval, subovate, or subspatulate in larger ones, the elongation being longitudinal when 

 occurring; the width of the lunule is usually greater near the under surface, especially in large 

 specimens. The whole form, including the margin, is thick, particularly so in large individuals. 

 The whole test is much depressed, being nearly flat along the front and sides; but rising toward 

 the center in a low longitudinally elongate mound which extends from about the middle of the 

 odd petal to the posterior border. The height of the mound varies directly with the size of the 

 specimen, ranging from less than an eighth to more than three-fourths of an inch. The apex 

 is central or subcentral, being usually slightly excentric anteriorly, though sometimes slightly 

 excentric posteriorly at the summit of the central mound, which is usually the anterior end 

 of the raised and thickened margin of the lunule. The depressed marginal area is more or 

 less distinctly corrugated by alternating low ridges and shallow troughs, there being two or 

 three troughs between the notches in the margin. The under surface is flat or slightly concave, 

 usually increasingly concave near the margin of the lunule. 



The ambulacral areas are narrow in the petaloid region, wide in the marginal region where 

 they about equal the interambulacral areas. The dorsal portions are petaloid. The petals are 

 large, unequal in length, divisible into a bivium and a trivium; those of the trivium usually sub- 

 equal in length, sometimes with the odd petal shorter than the other two, subelhptical or some- 

 what spatulate in form; those of the bivium much longer than the others, tapering gradually 

 from the distal ends toward the apical system, gracefully curved around the lunule, all the petals 

 open at the ends and extending about two-thirds the way to the margin. The poriferous zones 

 are wide, as wide as or slightly wider than the interporiferous areas; the inner rows of pores nearly 

 parallel and composed of rather large oval pores, outer row of smaller oval or elliptical pores at 

 the bottom of deepened portions of very narrow grooves by which the pairs of pores are 

 conjugated. 



