362 



Report of the State Geologist. 



decided than that in the genus Clathrospongia, and upon internal casts is 

 much obscured or even lost. 



About the aperture the vertical spicules are extended into a long and 

 narrow marginal tuft, apparently a single row of coarse and fine rods (mar- 

 ginaUa), such as occurs in the living species Bathydorus jhnbriatus* 



In figure 24 are 

 shown some of t he skele- 

 tal elements of this 

 sponge, the dermalia 

 being represented by 

 umbels, micrumbels, tri- 

 pinulus and echinate 

 pentactins, and the par- 

 enchymalia by smooth 

 siliquiform diactins. 



The Hgure at the bottom is a fragment of one of the main rods, partly decorticated ; £) I )R€)IS10RS. The 



among the others are umbels and micrumbels in various attitudes, smooth diactins, an 



incomplete tripinuius, etc. (j. m. c.) best preserved speci- 



men, which is incomplete at the lower end, has a length from aperture 

 downward of 155 mm. Its lower diameter is 75 mm.; its apertural diameter 

 in its compressed condition 150 mm. The marginal fringe in some places has 

 a length of 30 mm. A somewhat larger specimen which has been com 

 pressed almost vertically has an apertural diameter of 180 mm. 



Locality. In the shales of the Keokuk group at Crawfordsville, Indiana. 

 (Collection of A. S. Tiffany.) 



LYRODICTYA, Hall. 



Cyathiform Dictyosponges with regularly expanding, generally smooth 

 exterior, line net-work, low, erect tufts at wide intervals and very broad, 

 thick vertical bundles of rods and clemes, with no horizontal bundles of cor- 

 responding size. 



Type, Lijrodictya Romingeri, Hall. 



Ltkodictya Romingeri, Hall. 



Plate lvi, Fig. 1. 



18S4. Lyrodictya Romingeri, Hall. Thirty-fifth Ann. Rept. X. Y. State 

 Mus. Nat. Hist, p. 476. 

 Sponge broadly expanding; its form imperfectly known. Surface proba- 

 bly covered originally with low and erect lamellae; ridges with short tufts at 



Figure 24. Spicules of Ltbedlctya crinita, xiOO. 



•See Schul/.k, Hexact Inellldn, pi. lvlii, fig. l. 



