SpKCraS OF THK CHKMITN(J GrOITP, 07 



understaudiiig tliree distinct genera ; none of thene, however, are nodc.se species 

 of the Hydnoceuas type. 



The genus is well characterized, definitely restricted and most abundantly 

 developed in the Chemung sandstones of New York. 



Hydnocekas tubeuosum, Conrad. 



PLATE ", Fios 5-7; PLAT. i„, Fio-s. 1, 2,4; Platk iv, F.os. 2-.; P,.^tk v, F.oh. 3. 4; Pi.^rr. v., 

 Fig. 3; Plate vh, Figs. 2, 3; Plate vin, Figs. 1, 2; Platk xxxvm. Fio«. 1, 2. 



1842. Hydnocerm tuberosum, Conrad. Journal Philadeli.hia Academy of 

 Natural Sciences, vol. viii, p. 267, pi. xvi, fig. 1. 



1863. Dictyophyton tuberosum, Hall. Sixteenth Ann. Kept. N. Y. State Cab. 

 Nat. Hist., p. 90, pi. iii, fig. i. 



1880. Dictyophyton tuberosum, F. Roemer. Lethiea Pala3ozoica, part 1 

 p. 128. 



1883. Duityophyton tuberosum, Hinde. Catalogue Fossil Sponges British 



Museum, p. 130, pi. xxviii, fig. 3. 



1884. Dictyophyton tuberosum. Hall. Thirty-fifth Ann. Kept. N. Y. State 



Mus. Nat. Hist., p. 473, pi. 17 (18), figs. 7, 8. 

 Not Dictyophyton tuberosum, Barrois. Annales de la Soc. Geol. du Nord, vol. 

 xi, p. 82, pi. 1, figs. la-e. 1883. 



Sponge of ample dimensions, turbinate or obconical, expanding with 

 regularity ami moderate rapidity; aperture not contracted. Transverse sec- 

 tion of the Ijody of the cup normally subcircular or obscurely octagonal, but 

 usually subelliptical from compression. Surface bearing strong, elevated, 

 subangular nodes which are distinctly arranged in two series, one horizontal! 

 the other longitudinal. The horizontal rows do not, in any mature individual 

 obsei-ved, exceed four or five, and each row is separated from the next adjacent 

 by a regularly and broadly concave constriction. The vertical i-ows are, nor- 

 mally, eight in number, and these usually present the aspect of four double 

 rows, the concavity of the surface between adjoining double rows being notice- 

 ably deeper than that between nodes of the same double row. The effect of 

 this arrangement into double rows is heightened by the compression of the cup. 

 The nodes are low. subacute or blunt, with broad bases connected vertically 

 by sharp, slightly elevated ridges which cross the transverse constrictions, and 

 honzontally by quite shallow depressions. In the most slender examples 

 the height of these nodes, measured from the greatest depth of the horizontal 

 constrictions, is not more than one-seventh of the full diameter of the cup • 

 in robust individuals and young sponges it is very much less. 



