184 NEW YORK STATE MUSEUM 



2 inches in diameter; are approximately circular, with some irregu- 

 larities in outline, and the upper surface is broadly convex. Many 

 of them show the effects of compression in a rifting of the surface, 

 and so we are obliged to infer that these biscuit-shaped bodies were 

 originally nearly as convex as the bell of a jelly fish. The surface 

 is marked by monticules or acute elevations, distributed with appar- 

 ent irregularity and varying very much in number. There are 

 some in which these conicles are hardly apparent; others may have 

 ten or twelve, while still others twice this number. In the slab 

 which Mr Armstrong has sent me, there are at least eleven indi- 

 viduals, and he speaks of there having been more in the rock from 

 which these were taken. The accompanying illustrations will eluci- 

 date the character of these specimens better than any further 

 description, but it may be added that there is no clearly defined 

 indication of spicular structure on these surfaces ; further, that 

 the surfaces of the organism must have been very thin, for the 

 space between the outer and under casts is tenuous. Several of the 

 specimens show the peculiarity of a scar or a broken, disordered 

 spot at or about the center of the convexity, but as this is not 

 shown by all, it does not now seem possible to regard this as a 

 structural feature. 



Whatever may have been the full form of these sponge bodies, 

 there seems no evidence now that they were attached to the bottom 

 by any other means than their spreading growth or by the margins 

 of their reticulum. No specimen shows any evidence of an upright 

 or vertical stem or other form of support. As the species is very 

 sharply defined from C. allen'i and occurs in a different 

 horizon, it is here distinguished by the name Cryptodictya 

 t y 1 e a . Mr Armstrong reports that his specimens were found 

 loose in the gorge of Six Mile creek, 7 miles east of Erie, Pa., and 

 he is of the opinion that they must have come from something less 

 than one hundred feet above the base of the Chemung. 



3 A Branching Form of Silicious Sponge 



This sponge expresses a peculiar type of growth so unusual to 

 this reticulate group that its silicious character may be held in some 

 degree of reserve. The quadrate skeleton structure, however, seems 

 to be evident on various parts of the surface, and the probability is 

 that in the predominant silicious character of the great sponge fauna 



