Speciks of the Ciikmuno Group. 79 



Birnensions. A small, appai-eiitly entire individual has a length of 60 

 ram. and an apertural diameter of 50 mm. A larger e.vample, which is nearly 

 entire, is 110 mm. in length and of about the same width at the ui)per 

 extremity. 



Locality. In the lower beds of the Chemung group ; from a shaly sand- 

 stone at Deyo basin, Naples, Ontario county, N. Y., in association with Hydiu>- 

 ceras variaUle, Ceratodictya annulata, various In-achiopods of the Chemung 

 fauna and abundant remains of terrestrial plants, 



Hydriodictya nephelia, sp. nov. 



Plate xxi, Fig. 10. 



This species is represented by the upper portion of a flattened cup, 

 characterized by its broadly expanded and regular aperture and perfectly 

 smooth surface. The median or lower part of the cup tapers much less 

 rapidly than the apertural portion. 



The reticulmn is composed of extremely fine spicular bands, those of the 

 horizontal series being rather the more clearly defined. They occur at inter- 

 vals of about 4 mm. and form, with the divergent vertical lines, somewhat 

 trapezoidal quadrules. These spaces become obsolete toward the aperture 

 and the entire surface is minutely subdivided by the subordinate spicular 

 bands. 



The dimensions of the single example observed are as follows : length 

 108 mm. ; width at the lower end 65 mm. ; at the aperture 125 mm. 



Locality. In the upper beds of the Chemung group at Wellsville, N. Y. 

 (Collection of E. B. Hall.) 



PRISMODICTYA, gen. nov. 



1863. DictyophyUyn, Hall. Sixteenth Ann, Rept, N. Y. State Cab. -Nat. 



Hist., pp, 88, 89, 

 1882. Blctyophyton (partim). Hall. Notes on the Family Dictyospongidae. 

 1884. Dlctyophytoii (partim), Hall. Thirty-fifth Ann. Rept, N, Y. State 

 Mus. Nat. Hist., pp. 466, 469-471. 



Elongate, usually slender sponges, with acute, gradually expanding base 

 and sharply prismatic surface, the prism-faces numbering eight ; aperture 

 slightly contracted ; surface without tufts or lamellar ridges ; rarely with 

 inconspicuous nodes on or between the interfacial angles, 



Ty])e, Dictyophyton telum, Hall. 



