232 DlCTYOSPONGIDJS. 



PLATE XVII. 

 PRISMODICTYA, gen. nov. 



Page 79. 

 (S«« Plates XVUI, XIX, XX, XXI, XXVII, XXXIII, XXXIV, XXXV, XXXVI, XLI, XLII, LV.) 



Prismodictya pkismatica, Hall (sp.). 



Page 83. 

 (See Plates XXI and XLII.) 



Figure 1. An incomplete specimen showing a tendency to spiral growth. 

 Chemung group. Wellsville, New Yo?'k. 



Prismodictya banano, sp. nov. 



Page 87. 



Figure 2. The type-specimen, which is an essentially entire individual oi 

 very slender and gracefully tapering form. 

 Chemung group. Scio, Allegany county, Kew YorTc. 



Pbismodictya telum, Hall (sp.). 



Page 8C. 

 (See Plates XXXV and XLII.) 



Figure 3. Two individuals, one of them entire and with the normal propor- 

 tions of the species, the other somewhat imperfect and having a 

 curvature which appears to be the result of natural growth. Both 

 bear casts of spiral vermiform tubes or furrows. 



Figures 4, 5. Opposite sides of an entire individual. The surface represented 

 in figure 4, is somewhat worn but shows distant obscure horizontal 

 grooves ; that shown in figure 5, is slightly broken at the aperture 

 and has the horizontal grooves represented by sharper reticular 

 furrows. 

 Chemung group. Wellsville, New Yorlc. 



Figure 6. An entire individual of small size and undisturbed proportions, 

 showing the character of the reticulation and the form and size of 

 the aperture. Here as in figures 5 and 7, the prism-faces are made 

 to appear somewhat too concave. 



Figure 8. Basal view of the same specimen. 



Chemung group. Cattaraugus county, New York. 



Figure 7. A small entire example. 



