136 DlClYOSPONOID.E. 



is 4-5 mm. The other has a length of 42 mm., a basal width of 10 mm., across 

 the periloph, 18 mm. and across the aperture, 15 mm. 



The species is well characterized by its elongate form, small size and 

 the nature of its quadration. 



LiK-ality. In the upper Chemung sandstones at Wellsville, N. Y. (Col- 

 lection of E. B. Hall.) 



ARYSTIDICTYA, gen. nov. 



This genus comprises sponges which are cylindrical toward the base 

 but expand xipward to a broad, flaring aperture, the general form of the 

 sponge being like that of Lebedictya. The lower extremity is, however, 

 abruptly truncated by a circular, transverse or slightly convex diaphragm as 

 in TuYSANODicTYA and Phragmodictya. No basal frill has been observed. 



Surface smooth or with low, irregularly arranged nodes; more or less 

 distinctly reticidate. 



Apertural region with fine, branching channels running to the margin. 



Type, Arysiidictya elegans, sp. nov. 



Arystidictya elegans, sp. nov. 



Plate xli, Pig. 10; Plate xlii, Fio. 7. 



Sponge of considerable size. The single specimen has been compressed 

 but was undoubtedly circular at the base and regularly obconical for about 

 one third of its length, thence expanding abruptly to the very large aperture. 

 The form of the cup is, thus, somewhat broadly vase-shaped. 



Surface smooth, without nodes or other irregularities. Margin regular 

 and entire. 



The reticulnm as preserved appears to be composed, over the lower part of 

 the sponge, of rather sparse and loosely arranged spicular bands crossing at 

 right angles and forming square meshes about 4 mm. on a sitle. Whatever 

 subdivision of these meshes existed appears to have been quite irregular and 

 the principal quadrules themselves seem to be at times crossed by deviating 

 threads of the principal strands. Over the upper expanded surface of the cup 

 the reticulation is not distinctly visible, the surface being smooth or covered 

 with irrregularly distributed depressions, and toward the aperture these are 

 extended into grooves or branching channels, subparallel to one another and 

 perpendicular to the margin. 



The base of the sponge is truncated by a diaphragm the compression of 

 which has obscured the reticulation of the surface. 



