132 NEW YORK STATE MUSEUM 



pedicel other " heads " are seen bearing similar tufts. Immediately 

 below the white-banded ambital the base of another is seen. The 

 latter has lost its pedicel and distinctly bears a white ovate scar 

 with acute tip. Immediately above the thirteenth floor plate is one 

 of a series of larger apical plates which Schuchert calls the supra- 

 marginals. This plate bears also a similar white scar indicating 

 loss of its pedicel at one of the white division planes. The separate 

 plate of the radial column, set over the inner ends of floor plates 14 

 and 15, possesses also a whitened central area. Similar indications 

 of loss of pedicels from other plates should be noted, as Schuchert's 

 description of the genus states (1915, page 173) that all the apical 

 plates of the arm " excepting one or three middle columns, are 

 drawn out into more or less long, blunt, stout, erect, nonarticulating 

 rods." In plate 3, figure i, a single plate of the radial series is pre- 

 served but this still shows the base of a pedicel. In plate 6, figure 

 2, just below the middle of the figure, there are two supramarginals, 

 one each side of the median line, which still retain their pedicels 

 while others distinctly show the whitened area denoting planes of 

 separation. That the pedicels broke up into " beads " is also shown 

 near the lower right corner of this figure. 



Two large spines or spinelets are to be seen in plate i, figure i, 

 near the beginning of arm C. Their position indicates some dis- 

 placement. If they belonged to the axillary inframarginal at the 

 left, its orally directed pedicel (indicated in plate 10) bore at least 

 two heavy spinelets. These may be simple spines borne at the ends 

 of the first cover plates, but a comparison with the tips of the latter, 

 two pairs of which are also shown in this figure, would indicate 

 that these spines are rather too large to be assigned to such an 

 origin. 



In comparing the horizontal outlines of the inframarginals of 

 U . medusa and U. pulchella, we shall omit the pedicels 

 and measure only the plate bases. In plate 2, figure i, the longest 

 horizontal axis of these plates has the proximal end tipped in a 

 little toward the ray and the plates at the same time are imbricated 

 with the proximal apical ends slightly overlapping the plate nearer 

 the oral cavity, as in the fourth marginal of this figure. A long 

 axis, as near as we can measure, appears to be .75 mm long. The 

 diameter at right angles to this measures about .45 mm. In 

 U . pulchella, on the other hand (plate 7, figure i ; fourth, 

 fifth and sixth marginals of arm C next interradius d), these 

 marginals have a radial diameter of but .5 mm or one-third less 

 than in U . medusa, while their diameters perpendicular to 



