Report of the State Geologist. 



25 



from the Trenton limestone is described as Sfreptophyllum cystosum. A new 

 species from the Hamilton group is, as Lqphotasma earmatum, made the type 

 of a new genus. The Pctniia Fannirigdni, of Safford, is likewise made the 

 type of a new genus. The genus Duncanella, Nicholson, is also reviewed, 

 additional structural features determined, and some new specific forms 

 described. The paper is accompanied by a lithographic plate and numerous 

 text illustrations 



The Palaeozoic Hexactinellid Sponges Constituting the Family 



Dictyospongidae. 



Part I. 



This work was communicated with the annual report of last year, but on 

 account of its necessarily extensive illustration, the State printer was deterred 

 from producing it. The appreciative co-operation of the Wynkoop Hallenbeek 

 Crawford Company, the present State printers, and the endorsement of the 

 Hon. James A. Roberts, Comptroller of the State, have made its publication 

 at this time possible. It is proposed to present with this report that portion 

 of the work concerned with the general introductory discussion of the nature 

 and structure of these interesting fossils, and the description of such species 

 as are known to occur in the Silurian and Devonian formations. This will be 

 followed, in the next annual report, by accounts of other representatives of 

 this family occurring in the faunas of the lower Carboniferous formation. 

 This arrangement will make possible the publication of the one thousand 

 separate copies of this monograph which are called for by Chapter 932 of the 

 Laws of 18^5, without serious delay. 



The Dictyospongidm constitute a family of thin-walled, reticulate, siliceous 

 sponges whose life, so far as known, was restricted to palaeozoic time. The 

 first of these fossils to be described was regarded as a Cephaloppd and termed 

 Hydnoceras (JHydnoceras tuberosum, Conrad. Journal Philadelphia Academy 

 Natural Science, vol. viii. 1842); subsequently this and other species were 

 interpreted as remains of marine algae and a few species from the later 

 Devonian rocks became pretty well known to collectors of New York State 

 fossils. Their real nature was recognized about fifteen years ago by Prof. 

 R. P. Whitfield, from the study of specimens found in the soft calcareous 

 shales of Crawfordsville, Indiana, which retained the spicular skeleton of the 

 sponge in the condition of iron pyrites. 



