CHAPTER VI. 

 ECHINODERMS: ECHINOIDS. 



Melonites multipora Norwood & Owen. 



Plate xvi, figs, la-b; and plate xvii, ligB. la-c. 



Melonites multipora Norwood & Owen, 1846: Am. Jour. Sci., (2), vol. II, 



p. 222, figs. 1, 2, 3. 

 Melonites multipora Meek & WoTthen, 1866: Geol. Sur. Illinois, vol. II, 



p. 228. 

 Melonites irregularis Hambach, 1884: Trans. St. Louis Acad. Sci., vol. Ill, 



p. 549, pi. C, fig. 2. 



Test large, spherical, with 10 meridional folds, of which 

 the ambulacral are the narrower. Ambulacral areas about 

 two-thirds the width of the interambulacra, each composed 

 of about 10 rather poorly defined rows of very irregular 

 pore-plates, the ossicles of the central two ranges being 

 about three times as large as the others. The interambu- 

 lacral areas each have eight rows of hexagonal ossicles, the 

 marginal ones being only about half the width of the others ; 

 toward the poles, however, the plates are somewhat irregu- 

 lar and the ranges are not distinctly defined. The apical 

 disk is rather small in size; the oculars are very small, only 

 about one-fifth the size of the genitals, quadrangular in 

 outline, and so far as is known, have not been observed to be 

 perforated. The genitals are quite large, sub-pentagonal in 

 shape, one being slightly larger than the other four. The 

 madreporic plate is perforated by numerous very minute 

 openings, with apparently a single large one. The two gen- 

 itals nearest the madreporite have each four large perfora- 

 tions, and the two opposite each three. The number of holes 

 in the genital plates appears to differ somewhat in different 

 specimens. The oral aperture is rather small, subcircular in 

 outline. Five strong triangular jaws have been observed 



