170 



DiOITOSPONGIDjE. 



decided than that in the genus CiiATHKospoNoiA, 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 {ina/r- 



ginalia), such as occurs in the living species Bathydorus Jhnbriatus* 



In figure 24 are 

 shown some of the 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. 



FiQUBE 24. Sploulw Of LebtiMya crinita, s400. -1- 



The figure at the bottom Is a fragment of one of the main rods, partly decorticated j JJllftlBTlSiOTlS. 1 llC 



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



Incomplete tripinuius, etc. (J. M. c.) best prescrved 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, fine net-work, low, erect tufts at ^vide intervals and very broad, 

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

 responding size. 



Type, Lyrodictya Romingeri, Hall. 



Lyeodictya Romingeri, Hall. 



Plxtb lvi, Fiq. 1. 

 1884. I/yrodictya Romingeri, Hall. Thirty-fifth Ann. Kept. N. 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 



• See ScHULZE, IlexactlnelUda, pi. IvllI, flg. 1. 



