REPORT OF THE DIRECTOR I915 I25 



view of a portion of arm D of the holotype of U . p u 1 c h e 1 1 a 

 was given. The flooring plates there shown had lost a portion of 

 their oral surfaces by exfoliation. They display close sutures on 

 all sides and no trace of podial openings. 



The oral aspect of the floor plates differs very markedly from 

 the apical. In plate ii, figure 2, floor plate no. 23 of the right 

 row shows a broad inner end (in imbricated position?) from which 

 a narrow transverse ridge of uniform diameter runs to and abuts 

 against an inframarginal. This ridge, near the middle, bears a 

 marked angle projecting orally. It will be seen that the cover 

 plates, three of which are shown in the lower right corner of figure, 

 rest against the outer side of this angle when the arm is open. 

 Between these ridges and over the line of plate contact there is 

 thus left a groove with parallel sides, which is usually shown- 

 filled with sediment as in our figure. In this condition the outline 

 of a single plate resembles that of a round-headed tack. This 

 seems to be the appearance Schuchert had in mind when he stated 

 of this genus (1915, page 174), "Each plate is excavated laterally, 

 along a proximal edge, leaving a more or less long, slender podial 

 opening between adjoining plates." The floor plates of the left row 

 on our figure have lost more of their oral surfaces and present an 

 aspect somewhat like that figured by Schuchert (1915, plate 30, 

 figure 3) to show the podial openings of Urasterella gran- 

 d i s (Meek) and of which he says (page 298), " The podial open- 

 ings are situated laterally betv\^een the thinner ends of the ossicles.'* 

 The only other species of which Schuchert mentions the pores is 

 his U. girvanensis. His figure is in part copied from 

 Nicholson and Etheridge and shows somewhat diamond-shaped 

 openings (see his plate 28, figure 5). 



If now we examine plate 12, figure 2, we may clearly see a linear 

 series of comparatively large, black circles lying between the left 

 floor plates and their cover plates. These would most assuredly 

 be taken for outlines of podial openings by most students, but they 

 are truly the remains of organic structures lying wholly on the 

 oral side of the floor plates. It must be noted that the two apparent 

 pores nearest the twentieth cover plate seem to have double inner 

 walls. Here and elsewhere there are two distinct half circles 

 which, if completed, would cause the circles to intersect. We 

 must interpret these features as sections through the thin and more 

 or less crumpled walls of external ampullae or podia. This plate 

 affords another interesting example of the preservation of soft, 

 organic structures and of the value of the gum damar mounting 



