96 DiCTYOSPONOIDiE. 



1887. DlcUjophyton, Hall. Sixth Ann. Kept. N. Y. State Geologist, 



p[). 30-38. 

 1889. Jlydnocems, Beecher. Mem. Peabody Museum, vol. ii, pt. 1, p. 14. 

 1889. Dictyophyton, Neumayr. Die Stamme des Thierreichs, p. 228. 

 1895. Dictyophyton, Zittel. Grundziige der Palaeontologie, p. 52. 



Obconical, more or less rapidly expanding sponges, with an acute or 

 subacute base furnished with a short, often obscure tuft of anchoring spicules. 

 The surface, in elementary stages smooth, soon develops eight prism-faces and 

 thereafter prominent nodes arranged in horizontal and vertical rows, each 

 node normally lying at the intersection of adjoining prism-faces. These 

 nodes, therefore, correspond in number with the prism-angles, and are 

 normally eight in any horizontal row ; the number of horizontal rows in the 

 adult condition varying from four to eight. Abnormalities in place of 

 appearance of the nodes are not infrequent. The nodes may be small and 

 acutely triangular or very broad and semi-ovoid in outline. The extremity of 

 each is furnished with a small tuft of spicular rods. By the development of 

 the nodes the prism-faces of the body of the sponge are greatly obscured. 

 The surface also bears short erect lamellae connecting the nodes of any ver- 

 tical row, and it is probable that there were similar erect lamellae, both 

 .vertical and horizontal, which correspond to the principal reticulating bands. 

 About the aperture the surface is slightly expanded and the margin is smooth 

 and free of prostalia. 



Type, Hydnoceras tuheroBum, Conrad. 



Notwithstanding the fact that Conrad's term Hydnoceuas, based upon 

 the now well known s).ecies, //. tuberosum, was introduced under the con- 

 ception that the fossil represented an aberrant or extravagant type of orthoceran 

 cephalopod, there is nothing in the etymological construction of the name that 

 of itself conveys any erroneous notion of the structure. Consequently it seems 

 proper to rehabilitate this finely characterized genus of sponges ^vith its first 

 appellation, and restore to Mr. Conrad the credit for its discovery and first 

 description. It was, in fact, at Mr. Conrad's own suggestion, that his name 

 gave \vay to the later term Dictyophyton,* and, as else\vhere observed, 

 although this term has been generally adopted in the literature of these 

 fossils, it seems the wisest plan to discontinue it, not because it was founded 

 on a misconception but because it perpetuates one. The specified type-species 

 of Dictyophyton were three in number, representing according to our present 



* See Sixteenth Ann. Kept. N. Y. State Cab., p. 87. 



