BiBMooRAPinr. 41 



highest development upon the sands and arenaceous muds of the upper 

 Devonian, and among them are those most frequently provided with a root 

 tuft. The species of the Keokuk group grew on a soft muddy l)ottom like 

 many of their modern representatives, accompanied by a profuse growth of 

 crinoids and Avith many mollusca and brachiopoda ; and wliile some of tlie 

 species of the latter fauna are provided with root-tufts, the majority have 

 broad bases indicating a sessile mode of growth on solid objects such as 

 stones or dead shells, 



HISTORICAL. 



Bibliography of the Dictyospongid^ 

 1842. 



1. T. A. Conrad. Observations on tlie Silurmn and Devonian Systems of 



the United States, with descriptions of New Organic Jienmins. (Proc. 

 Acad. Nat. Sci. Philadelphia, vol. 8, pp. 267-8, pi. xvi, fig. 1.) 



Describes the genus PIydnockras and the species H. tuherosuni, stated to 

 be from the Chemung sandstones near Addison, Steuben county, N. Y. The 

 author's account of this sponge was based on an internal cast which he con- 

 ceived to represent an extravagant form of cephalopoda. 



2. L. Vanuxem. Geology of New York; lieport on the Third District, 



pp. 182-3, fig. 60. • ' 



A brief description is given, with a figure of an incomplete specimen 

 of Uphantcenia (Ilyphantcenia) CJiemungensis, obtained from the Chemung 

 sandstones " near the south end of the Ithaca and Oswego railroad." The 

 author expresses his belief that the fossil was a marine plant. A figure 

 of the original specimen will be found among the plates of this voliune. 



1852. 



3. Frederick McCoy. A systematic Description of the British Palaeozoic 



Fossils in the Geological Museum of the University of Cambridge, 

 p. 62, pi. 1. D,figs. 7,8. 



Under the name Tetragonis Danbyi, the author describes a species of 

 DiCTYOSPONGiA from the upper Ludlow rocks of AVestmoreland, evidently 

 regarding the fossil a cystidean. It is placed among the EchinalermMa 

 in Morris's Catalogue of British Fossils, p. 90, 1854, Murchison's 

 Siluria, third edition p. 536, 1859, and fourth edition, p. 509, 1872. In 

 Salter's Catalogue of tlie Cambrian and Silurian Fossils contained in the 



