Explanation of Plate 9. 



Figure 49. — Melonites sepfenarius, Whitfield. In tlie ambulacrum onlj- a portion of 

 the left half is complete, showing columns a, a\ with two interme- 

 diate columns, and one column, h\ of the right lialf. Column 7 in 

 the interambulacrum has 5 columns on the left and 1 on the right. 

 This is the most extreme irregularity in the position of a column of 

 any echinoid seen. Pentagonal plate P and heptagonal i)late A, are 

 local and most unusuai irregularities. Warsaw group, Subcarbonif- 

 erous, Buzzard Roost, Franklin count}^ Alabama. Specimen in 

 American INEuseum, New York. Life size. Page 182. 



Figure 50. — Oligoponis missouriensis, Jackson. Ambulacra have fan-shaped plates 

 opposite the sutures of interam])ulacral plates. Interambulacra have 

 5, as in area C, or 6 columns of plates ; when the latter, only for a brief 

 period, as in area ^. Adambulacral plates are rounded on their outer 

 borders (compare with plate 6, figure 30). Irregular pentagons and 

 heptagons (see text). Subcarboniferous, Webb City, Missouri. Speci- 

 men in Museum of Comparative Zoology, catalogue number 3078. 

 Life size. Pages 150, 184. 



FiGi'RE 51. — The same. Ambulacral detail of one half-area. ^Magnified 2 diam- 

 eters. Page 184. 



Figure 52. — The same, showing genital and ocular plates. Magnified 2 diam- 

 eters. Pages 156, 180. 



Figure 53. — LepidestJws worOieni, Jackson. Ambulacrum B ventrall}' has 4 columns 

 of hexagonal plates (compare with Melonites, plate 2, figure 2) ; at 

 the ambitus there are 8 columns of subhexagonal i)lates. Pores are 

 in the center of the plates. Interambulacra A and C ventrally have 

 4 columns of plates ; one of these columns drops out (see area C, 

 plate A) in passing dorsally, and three columns continue to the 

 dorsal pole. Two dental pyramids, />, D, are visible ventrally. 

 These are seen plainly on the other side of specimen. Incrusting 

 bryozoa obscure some details. Keokuk group, Subcarboniferous. 

 Specimen in the Boston Society of Natural History, catalogue num- 

 ber llGOl. INIagnitied 2 diameters. Page 207. 



Figure 54. — Pholidocidaris meeki, Jackson. Ambulacral plates liave central pores 

 surrounded by a depressed areola. Interambulacrum has ventrally 

 a single plate, 1^, and passing dorsally new colunms are added up to 

 (). In column 2 plates are apparently wanting, as indicated by the 

 dotted line, and an ambulacral plate. A, has been shoved out of 

 place. A few spines are scattered over the test ; dental pyramids, 

 D, exist ventrally. Below plate V is a plate which is ai)i)arently 

 an interainl)ulacral plate of the peristome. Keokuk group, Sub- 

 carboniferous, Warsaw, Illinois. Specimen in Museum of Compar- 

 ative Zoology, catalogue number 3070.. Life size. Page 210. 



Figure 55. —Immature (Mdaris j^dpUlcita, Leske; showing resorption of corona by 

 encroachment of the peristome. Spine tubercles are being cut away 

 together with the plates. Showing also imbricating interambulacral 

 plates of the peristome. Recent (compare with plate 8, figure 48). 

 After Loven (Echinologica, page 22). Magnified. Page 215. 



254 



