gg DlCTYOSPONGIUvE. 



This species will be readily recognized by its persistently slender and 

 graceful form and subprismatic surface. Among the examples figured one is 

 given which again shows that a spiral mode of growth, such as that ali-eady 

 shown to occur in specimens of P. telum, occasionally manifests itself here. 



Bimensions. The best preserved specimen has a length of 90 mm. Its 

 greatest width, one- third of its length from the base, is 13 mm,; at the 

 aperture the width is 9 mm. 



Locality. Several specimens of this form have been found in the upper 

 sandstones of the Chemung group at Friendship, Allegany county. (Collec- 

 tion of E. B. Hall.) 



Prismodictya aulophia, sp. nov. 



Pij^TE XX, Figs. 7, 8 ; Plate xxxiv, Figs. 4, 5 ; Plate xli, Fig. 7. 



Sponge of moderate size, gradually expanding to its full width at about 

 two-thirds of its length, again contracting towards the aperture. Surface 

 with deeply concave prism-faces and elevated prism-angles. Each prism-face 

 is divided medially by a vertical spicular band, which is clearly defined on all 

 specimens. These and the longitudinal bands upon the prism-angles, bound 

 opposite sides of major quadndes about 6 mm. square, the reticulum over each 

 of these areas being extremely fine. A small specimen which appears to be 

 complete, is 50 mm. in length and 27 mm. in diameter across the upper ex- 

 tremity. A fragment of a larger cup measures 85 mrii. in length, and the 

 entire length, judging from the inclination of the sides, was upward of 

 100 mm. The concave, fluted surface of this sponge renders it unlike any 

 other here described. 



Localities. This species has been found in numbers in some blocks of 

 compact and finegrained red sandstone, belonging to the upper beds of the 

 Chemung group, at Wellsville ; less abundantly in greenish and more argilla- 

 ceous layers at the same locality, and, also, in pome abundance in a greenish 

 siliceous sandstone at Scio, N. Y. (Collection of E. B. Hall.) 



Pkismodictya ptionia, sp. nov. 



Plate xxxiv, Fig. 3. 



This sponge is of rather large size and of somewhat similar aspect to the 

 smaller species, P. cithara and P. cercidea, the cup expanding rapidly 

 from a narrow, doubtless somewhat extended stalk into a broad and inflated 

 body whose prism-faces are gently concave. At, or just above, the greatest 

 width of the sponge, low nodes are formed on the prism-angles, as in the 



