122 DlCTYOSPONGID^. 



genus some forms which, \vhen better known, may prove to belong in some other 

 association. Indeed, in the type-species only are the generic features clearly 

 defined, and hence the group must for the time being . serve in a measure as a 

 convenient receptacle for certain imperfectly known forms. 



Type, Cluth-ospongia abacus, Hall. (See description of this form among 

 the sjiecies of the Waverly group.) 



CliATIIROSPONGIA FENESTBATA, Hall (sp.). 

 Plate xiv, Fig. 2; Plate xxv, Fig. 5. 



1863. Bktyophyton fenestratum, Hall. Sixteenth Ann. Rept. N. Y. State 



Cab. Nat. Hist., p. 90, pi. iii, fig. 4. 

 1884. Dictyophyton femstraPum, Hall. Thirty-fifth Ann. Kept. N. Y. State 



Mus. Nat. Hist., p. 469. 



The original specimen of this species is a very incomplete fragment of a 

 moderately large cup, a portion of whose surface, involved in soft green shale, 

 retains the exterior character of the reticulation, while the remainder of the 

 specimen is only an internal cast of the skeleton. This specimen gives no 

 accurate idea of the form of the cup, except that it was subcylindrical with an 

 essentially smooth exterior, but an internal cast of a more complete example 

 from the same locality as the original furthers our knowledge of the species. 



Sponge of considerable size, elongate subcylindrical through most of its 

 length, with a short, rapidly expanding basal portion. Transverse section 

 subelliptical or subcirculai". Surface with only traces of low nodes at the 

 angles of the principal quadi'ules. 



ReticAtlmii in its external character, composed of (juadrules of ^vhich the 

 principal series measures about 12 mm. on the side. The honzontal and ver- 

 tical bands of the first series are of about equal prominence and at their inter- 

 section distinct nodes are formed. These main quadrules are regularly sub- 

 divided by four subordinate series of spicular bands and upon the internal 

 cast almost all distinction between these series is lost, the ultimate subdivision 

 of the quadrules being nearest the internal surface of the cup. 



It is evident that the principal spicular bands were produced outwaj-d in 

 the form of free lamellae ; at one spot on the cast these show a width of 

 about 2 mm. 



Dimensions. The original specimen has a length of 105 mm. and a width 

 of 45 mm. A second example measures 138 mm. from base to distal 

 extremity, and for five-sevenths of this length the diameter of the cup is 

 45 mm. The basal cone has a length of about 30 mm. 



