1 30 DlCTYOSPONOID^. 



broader and the primary surface quadrules more nearly equilateral than in 

 that species ; yet it is probable that further knowledge will demonstrate the 

 superfluity of this specific name. 



• Locality. In the Chemung group, associated with Sjpirifer disjunctus; 

 Warren, Pennsylvania. 



TlIYSANODICTYA SACCU8, Sp. nOV. 

 Plate xxv, Figs. 1, 2. 



Sponge short, stout, broadest at the base, narrowing upward, with gently 

 incurving margins. Height somewhat less than the basal diameter. Circular 

 or subelliptical in cross-section. Basal obcone or diaphragm moderately deep 

 with a subcentral apex. 



Meticulum. Primary quadrules somewhat variable in size, smaller and 

 more nearly square than in Thysanodictya riidis. Subordinate divisions of 

 the net-work clearly shown in j)laces. The basal diaphragm is thickened 

 or nodose about the edges and, in the specimens observed, has a some- 

 what irregular reticulation, though the meshes of the lateral surfaces ai-e here 

 to some extent retained. This species may be recognized by its short and 

 robust form and its tapering rather than expanding cup. Two individuals 

 fi'om different localities sho^v the same characters. In the better of these, one 

 surface is covered ^vith low, apparently concretionary tubercles which, in a 

 measure, obscure the character of the reticulum ; a phenomenon not infre- 

 quent among these fossils. 



Dimensions. A typical example has a length of 74 mm., a basal 

 diameter of 88 mm., and an apertural diameter of 63 mm. A second specimen 

 has nearly the same proportions. 



Localities. In the upper part of the Chemung group, at Wellsville and 

 Whitesville, Allegany county, N. Y. (Collection of E. B. Hall.) 



Thysanodictya Johnstoxi, sp. nov. 



Plate xxiii, Fiqs. 7, 8. 



Sponge robust, subcylindrical or somewhat inflated medially, and sharply 

 constiicted above the base. Basal obcone or diaphragm very shallow, nearly 

 flat ; sharply and irregularly nodose about the margin. The surface of this 

 diaphragm is composed of fine and sharp spicular bauds intersecting at right 

 angles, the i)revailing (piadrule measuring from 3 to 5 mm. on a side. There 

 are no coarse spicular lidges of a higher order distinguishable, but the reticu- 

 lum shows, in addition to the regularly intersecting bands, iri-egularly arranged 

 or disordered bands piincipally of large size. The nodes of this basal surface 



