358 



Report of the State Geologist. 



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

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

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

 being frequently subdivided by subordinate series of spicules. The general 

 aspect of the specimen is like that of Lyrodictya, 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 812, part 1.) 



DlCTYOSPOXGIA CYLINDRICA, Whitfield (sp.). 

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



1881. Dictyopliyton eyli iidi'icum, Whitfield. Bull. No. 1, Amer. Mus. Nat. 



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

 1884. Dictyopliyton cylindricum. Hall. Thirty-fifth Ann. Rept. N. Y. State 



Mus. Nat. Hist., p. 475. 



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

 cylindrical or elongate obeonical 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 vertic«i spicular rods disposed at numerous 

 and somewhat unequal intervals in small bundles. 

 The outer or dermal quadrules are formed by 

 cruciform spicules, and measure about .5 mm. on 

 each side. Microscopic examinations of the 

 reticulum reveal among the parenchymalia or 

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

 curved diactins and fragments of minute eehinate 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 calcaivous shales at Crawfordsville, Indiana. 



Fioubb 32. Spicules of Dictyotpongla cylin 

 drica, x«00. (J. M. C.) 



