Species of the Chkmuno Gkoup. 73 



DiOTYOSPONOIA 8CKPTRITM, Hall (sp.). 

 Plate xiv, Fios. 3-6; Plate xv, Fios. 8, 9; Platk xvi, Fioh. 3, 4 ; Platf. xxvil, Pio. 3; 



PlJkTE XXXVI, Fio. 7. 



1890. Dictyophyton sceptnim, Hall. Ninth Ann. Rept. N. Y. State Geolo- 

 gist, p. 56 ; and Forty-third Ann. Rept. N. Y. State Museum of 

 Natural History, p. 258. 



Sponge elongate, conical or subcylindrical ; circular or elliptical in trans- 

 verse section. Usually abnormally compressed, sometimes curved. Very 

 gradually expanding from the base upward for one-half to two thirds its length, 

 narro-wing more abruptly toward the aperture. 



Surface smooth or without prism-faces or any iiregularities except those 

 arising from distortion in fossilization. 



Reticulum characterized by coarse, subequidistant transveree spicular 

 bands, from 10 to 15 mm. apart, crossed by vertical bands of subequal size not 

 more than one-half of this distance from each other. The impressions left by 

 the .vertical bands are not as deep and conspicuous as those of the horizontal, 

 hence the first effect produced by the appearance of the specimens is that of a 

 strong transverse lineation, and a secondary and very characteristic impression 

 that of a division of the surface into vertical, elongate rectangles. Some of the 

 specimens Avhich have been enveloped in a soft clay-shale, retain the spicular 

 bands themselves, changed through pyritization and o.xidation into limonite, a 

 very unusual occurrence in species from the Chemung sandstones. This pres- 

 ervation is insufficient to demonstrate the character of the individual spicules, 

 though it shows the very fine reticulation of the primary quadrules. 



Dimensions. The specimens at hand show considerable variation in fonu 

 and size. The most robust of these, in which the aperture is retained Avhile 

 a small part of the basal portion is lost, has a length of 200 mm., a width 

 at the base of 40 mm., greatest width at two-thirds its length from the base, of 

 70 mm. and a width at the aperture of 50 mm. This specimen has unquestion- 

 ably been much flattened, which accounts for its great proportional width. 

 A more slender cup, nearly complete from base to apertui-e and but slightly 

 compressed, measures 252 ram. in length and 38 mm. in greatest width. In 

 one example the cup is greatly curved, but instances of this kind seem to be 

 due to the easy distortion of such long and slender bodies. 



LocaUties. In the shaly sandstones of the upper part of the Chemung 

 group at Alfred, Scio, Friendship, Nile, Andover, Cuba and Wellsville, Allegany 

 county ; Olean, Cattaraugus county, and Jamestown, Chautauqua county, N. Y. 



