166 DlOTYOSPONGID^. 



of the vertical spicular Inuidles toward the base and extending upward in one 

 or two broad and irregular strands. The reticulum is fine-meshed and over 

 most of the surface the prevailing quadrille has a diameter of about 3 mm., 

 being frecpieutly subdivided by subordinate series of spicules. The general 

 aspect of the specimen is like that of Lybodictya, and the species is therefore 

 provisionally referred to this genus. 



Dimensions. Length of the fragment 135 mm., greatest width 130 mm. 



Locality. In the yellow sandstone below the Burlington limestone, Bur- 

 lington, Iowa. 



SPECIES OF THE KEOKUK GROUP. 



DICTYOSPONGIA, gen. nov. 

 (For description see page 72, part 1.) 



DiCTYOSPONGIA CYLINDRIOA, Whitfield (sp.). 

 Plate lv, Fig. 3; Plate lxi, Fig. 6. 



1881. Dictyophyton cyliiulriciim, Whitfield. Bull. No. 1, Amer. Mus. Nat. 



Hist., p. 19, pi. iv, fig, 3. 

 1884. Dictyophyton cylindrimim, Hall. Thirty-fifth Ann. Rept. N. Y. Stat© 



Mus. Nat. Hist., p. 475. 



The original specimen of tliis species is a fragment of a flattened sub- 

 cylindiical or elongate obconical tube, exposing, for the most part, the inner 

 portions of the reticulum but also showing that the exterior of the sponge 



was devoid of ornamental features. The ex- 

 posed surface exhibits fine smooth horizontal 

 and vertical spicular rods disposed at numerous 

 and someAvhat unequal intervals in small bundles. 

 The outer or dei-mal quadrules are formed by 

 cruciform spicules, and measure about .5 mm. on 

 „ .«,„.. . ^ each side. Microscopic examinations of the 



FlODUl 33. SplculM ot Dietyotpongia oyUn. -C 



<ir«>o.x«oo. (J.M.C.) reticulum reveal among the parenchymalla or 



dermalia, umbels of a form somewhat different from those in Cleodictya, 

 curved diactins and fragments of minute echinate hexactins. 



This species seems to be of rare occurrence ; besides the original speci- 

 men, there are, in the material in hand, only one or two small fragments, so that 

 the species is still quite imperfectly known. The typical example has a length 

 of 60 mm. and a width of 56 mm. 



Locality. In the calcareous shales at Crawfordsville, Indiana. 



