Fossil Reticulate Sponges. 481 



Physospostgia alternata. 



Plate 20, Fig. 9. 



Physospongia alternata, Hall. Notes on the Family Dictyospongidae ; pre- 

 lim.' for the 35th Rept., pi. 19, %. 9. 1882. 



Cap cylindrical. Proportions of length and breadth unknown. 

 Base unknown. 



Substance consisting of closely reticulated tissue, with stronger 

 longitudinal and transverse bands of spicules, which divide it into 

 twelve longitudinal rows of qaadrules; these are alternately elevated 

 and depressed. 



The fragment described has a length of about 45 mm.; in its com- 

 pressed condition it has a greatest width of 25 mm., and the shortest 

 diameter is 10 mm. 



Formation and locality. In the shales of the Keokuk group; 

 Crawfordsville, Ind. 



Uphant^enia Chemungensis. 



Uphantmnia Chemung 'ensis. Vanuxem. Rept. 3d Geol. Dist. N. Y., p. 183, fig. 



50. 1842. 

 Uphantamia Chemungensis (Vanuxem). Hall. Sixteenth Rept. State Cab., p. 



86. 1863. 

 Not Uphantcenia Chemungensis (Vanuxem), Dawson. Quarterly Jour. Geol. 



Soc. London. 1862. 



Frond circular or subcircular, gently convex on the lower side, with 

 a depression in th'e middle ; consisting of continuous bands radiating 

 from a central point or defined central area, increasing in width as 

 they recede from the center, and arranged at subequal distances from 

 each other. The entire number of these radiating bands is thirty-two, 

 every fourth one being stronger than the intermediate ones. These 

 radiating bands are crossed concentrically, but not intersected, by 

 another set of bands which are of equal width throughout their ex- 

 tent, each successive one being a little wider than the preceding, until 

 the frond is completed. The interstices between these bands are en- 

 tirely free from any substance in the original frond, and as preserved 

 in the rock, the interspaces are filled with the substance of the matrix. 



The surface of the frond, both in the radiating and concentric 

 bands, is similar, and shows evidence of fine striations, and was, 

 doubtless, finely reticulate. Where these bands cross each other, there 

 is no proper intergrowth, but a double thickness of the tissue is ob- 

 servable, while each band maintains its independent growth and 

 limitation. 



The original specimen, from center to circumference, has an extent 

 of 155 mm.; across the greatest width, at right angles to this, it 

 measures 140 mm. The largest specimen known has a greatest 

 diameter of nearly 350 mm., the semi-diameter on the most extended 

 side is 190 mm. 



Formation and locality. In the fine grained sandstone of the upper 

 Chemung group ; near Owego, N. Y. 

 [Sen. Doc. No. 38.] 61 



