172 NEW YORK STATE MUSEUM 



PAKOPSONEMA CRYPTOPHYA 



A peculiar echinoderm from the Intumescens-zone (Portage 



beds) of western New York 



BY JOHN M. CLARKE 



(Plates 5-9) 



WMle prosecuting paleontologic work in the Portage form- 

 ation of western New York during tlie season of 1895, D. D. 

 Luther brought to light a number of interesting hexactinellid 

 sponges or D i c t y o s p o n g i d a e at the horizon of the Portage 

 sandstones in the Tannery gully at Naples N. Y. These proved 

 to belong largely to the genus H y d n o c e r a s and constitute 

 the first evidence obtained of the existence of such bodies in this 

 formation. Among them was a single incomplete fragment, show- 

 ing a radial surface structure modified by fine, interrupted cross- 

 lines, that give the surface of the body a plaited aspect suggestive 

 of minute basket work. The body, through incompleteness and 

 obscure retention, failed to explain itself or even suggest its true 

 nature, though it was clearly evident that it had no relation to the 

 sponges with which it was found. In the season of 1897, Mr 

 Luther obtained from a loose slab of Portage sandstone in the 

 vicinity of the former locality several specimens of this fossil in 

 so complete a state as to justify the inference that all the parts 

 capable of preservation in such sediments are here retained. 

 Since then he has been successsful in locating the stratum con- 

 taining the fossil. These specimens are in different conditions 

 of excellence; one has suffered little modification in outline, 

 another is but slightly irregular in its periphery, and of the rest 

 only portions greater or less are preserved. v 



The fossil is discoid and of quite regularly elliptic outline; 

 the one best preserved has a length of 190 mm and a width of 

 160 mm^ the original shell being thus of no inconsiderable size. 

 The thickness of these large disks is very slight. We shall pres^ 

 ently observe the total difference in the aspect of the upper and 

 lower surfaces, and yet some of the examples show that between 

 these surfaces there was but a very narrow space. In the speci- 

 men represented by the two figures, plates 6 and 7, which are 



