PAROPSONEMA CRYPTOPHYA ♦ 177 



radial bands, which at the center of the disk are not less than 25 

 and are probably as many as 50 in number. These increase by the 

 simple bifurcation of the long and narrow interambulacral spaces, 

 at two distinct. ontogenic periods, so that the outcome of this sub- 

 division is three slightly interpenetrating cycles of ambulacral 

 bands. No oral, genital or anal structures have been determined. 

 The center of the surface is the point of convergence of all the 

 ambulacral bands and is smooth or has not retained essential 

 structural details. The existence of geometric plates on these 

 ambulacra is shown in only a few places; most distinctly along 

 the edges of the interambulacral spaces of the second cycle, where 

 the lateral ends of the ambulacral plates make a visible notching 

 of the margin, and again now and then the horizontal edges of 

 the perforate plates are shown. In no part of the fossil is there 

 evidence of plates on the imperforate surfaces. 



The evidence of the presence of plates over the ambulacra 

 is definite though imperfect, but their apparent total absence 

 on the major parts of the surface of the body prompts the fol- 

 lowing suggestion. The matrix of the fossils, a highly laminated 

 or '^ reedy " silico-felspathic sandstone, contains, in the Tannery 

 gully at Naples, dictyosponges and considerable masses of 

 comminuted floatwood, but no fossils with calcareous test of 

 considerable thickness. Elsewhere this same Portage sandstone 

 is not infrequently found to contain joints of crinoid columns pre- 

 served in the usual crystalline calcite. If these echinoid bodies, 

 which we propose to term Paropsonema cryptophya, 

 possessed a calcareous test in any degree corresponding to their 

 considerable size, we should expect to find even in this arenaceous 

 matrix some direct or at least more reliable indirect evidence of 

 its presence. It may, therefore, be well to consider whether these 

 fossils were not provided for the most part with a leathery or 

 imperfectly calcified integument. 



The foregoing description gives an account of the characters 

 of this singular fossil so far as it seems possible to make them 

 out. These are so unusual and so different from structures pre- 

 sented by the fossil and recent E c h i n o d e r m a t a that it 

 would be venturesome to make farther suggestions as to the prob- 

 able affinities of the organism. The specimens and drawings 



