Reviews — Hall 8f Clarke — Palceozoic Sjjonges. 231 



of the piQule, and a comparatively new form, termed an umbel, 

 consisting of a plump rod with an umbrella-shaped summit. There 

 are also rods with anchor-shaped terminations as in recent sponges 

 of the same group. 



The Dictyospongidae in the Chemung rocks of New York are 

 not infrequently met with associated together in large numbers in 

 particular beds of a somewhat coarse sandstone, in which they lived 

 and flourished in large colonies. This habitat is in striking contrast 

 to that of recent hexactinellid sponges, of which the greater number 

 live in mud or ooze and often at considerable depths, whereas the 

 sandy matrix on the surface of which their Devonian progenitors 

 lived indicates a comparatively shallow sea. 



The Bibliography of the Dictyospougidse is not without interest. 

 The earliest known example, Eydnoceras tuberosum, was thus named 

 by Conrad, in 18i2, under the supposition that it was an unusual 

 form of Cephalopod, and in the same year Vanuxem described 

 Uphant(snia Chemungensis, another member of the family, as a marine 

 plant. In 1863 James Hall, the senior author of the present 

 monograph, proposed a new genus, Dictijophyton, with nine species, 

 including Eydnoceras tuberosum, Conrad, the generic name signifying 

 that in Hall's opinion the fossils belonged to marine Algae. That 

 these supposed fossil plants were in reality siliceous sponges related 

 to the recent Euplectellidse, was clearly shown by E. P. Whitfield 

 in 1881, who pointed out that in this case the generic term 

 Dictyophyton, Hall, was a misnomer, and that therefore it would 

 be necessary to go back to one of the earlier names, Eydnoceras, 

 Conrad, or TJphantcenia, Vanuxem. In 1884: Professor Hall defined 

 several new genera, but though the spongoid character of the family 

 is fully recognized in the name given to it, the term Dictyophyton is 

 retained, and the same course is followed in 1890, when other new 

 species were placed in the genus. In the meantime a large collection 

 of these fossils had been gathered together by Professor Hall, who 

 handed them over to Dr. J. M. Clarke for revision, and it may 

 therefore be fairly assumed that this latter author is mainly 

 responsible for the classification and descriptions in the present 

 monograph. We find in it a veritable revolution as regards the 

 nomenclature : the name Dictyophyton, Hall, is entirely given up, 

 since it "has proved a misleading term among the sponges"; 

 Conrad's genus Eydnoceras, which Hall had merged in Dictyophyton, 

 is again revived, and the various species placed under Dictyophyton 

 by Hall, and by others who had adopted the generic name without 

 reference to its original signification, are now distributed among 

 Eydnoceras and ten new genera ! 



A summary of the monograph shows that the Dictyospougidse 

 family is divided into 7 subfamilies, all new ; 32 genera, 20 of 

 which are new ; and 128 species, of which 77 are new. The 

 descriptions of genera and species are drawn up very carefully, but, 

 as already remarked, the structural characters of the skeleton in 

 these sponges are very imperfectly shown in their casts, and 

 differences of mere outer form and mode of growth, on which many 



