84 DicnrospoNGiD.E. 



major quadrilles predominating, at others these being obscured by the lesser 

 meshes. At the intersections of the prism-angles with the horizontal spicular 

 bauds, the internal casts show small pits whicli probably indicate the presence 

 at those points of spicular tufts. All the principal bands, and perhaps, also 

 the subsidiary bands, were extended laterally from the body of the cup into 

 narrow, erect lamellae, from .5 to 1 mm. in width. 



Dimenshm. An average specimen which is nearly entire has a length of 

 i)0 mm. ; its diameter at the base is 8 mm. and at the top 27 mm. Incomplete 

 specimens of larger individuals having similar dimensions abound. In one 

 specimen there is no increase in diameter in a length of 80 mm., examples of 

 this character being of somewhat less frequent occurrence than the others. 



This sponge is not widely different from those described as Prisniodictya 

 parallekt,, and when both are better known it may prove that the more regu- 

 larly prismatic forms here descnbed are identical ^vith that species, but at 

 present there seems no sufficient ground for separating the various forms of 

 P. pristnatica, all of which occur in association. 



Localities. In the upper beds of the Chemung group ; in great numbers in 

 a light grey sandstone at Concord, Erie county, Pennsylvania ; also at Wells- 

 ville, Allegany county, Olean, Cattaraugus county, N. Y., and at "Warren, 

 Pennsylvania. 



Prismodictya Allegania, sp. nov. 



Plate xx, Fig. 4. 



Sponge large, octagonal in cross-section, prism-faces clearly but not 

 sharply defined ; each divided by a more or less prominent median vertical 

 ridge and rendered thereby somewhat convex. Basal portion rounded, the 

 prismatic surface being undefined for about one-fifth of the length of the 

 sponge. The expansion of the cup is gradual for nearly two-thirds of its 

 length where the greatest diameter is attained ; the upper part is considerably 

 expanded and again contracted towards and about the aperture. 



Meticulum. The prevalent major quadrules are formed by the intersec- 

 tion of low horizontal bands with those on the prism-angles and on the middle 

 of the prism- faces. These average about 9 mm. across the base and 11 mm. 

 in height. The subordinate reticulation is, as a rule, quite clearly retained to 

 the fifth or sixth degree. 



Dimensions. The largest specimen observed, which is incomplete at the 

 basal extremity and for a short distance near the aperture, is 210 mm. in 

 length, 53 mm. wide at the lower end and 75 rnna. in diameter at the greatest 



