148 DlCTYOSPONGID^.. 



horizontal ridges in the total length of the sponge. There is still another 

 feature in which this species diifers from H. tuberosum, viz. ; (5) the preva- 

 lence of a very fine network, the meshes being of subequal size, contracting 

 over the constricted areas. Large quadrules such as are usually found in 

 H. tuberosum are wanting. Professor Babrois's excellent figures of this species 

 show the curvature of the sponge, which seems to be probably an accidental 

 feature of the specimen. 



Locality. In compact greenish sandstone of the Psammites du Condroz 

 (=Chemung group of New York), Jeumont, Brittany. 



Hydnoceuas Jeumontense, sp. nov. 



Plate xlvi, Figs. 5, 6. 



This form is represented by several more or less compressed speci- 

 mens in which the cup is broad and has somewhat the aspect of the 

 Chemung species, H. pJiymatodes, though Avith coarser, less abundant and 

 less regular nodes. 



The form of sponge is rather broadly turbinate, its lower portion being 

 distinctly prismatic for a considerable distance from the apex. The horizontal 

 constrictions appear to be rather narrow and shallow, while the node-bearing 

 ridges are decidedly elevated and often quite broad. The nodes themselves 

 are elongate and those of the vertical rows are more or less distinctly con- 

 nected by the ridge at the angle of the prism-faces. A remarkable character 

 of the species is the rapid multiplication of nodes. At the base of the sponge 

 the number of the prism-faces appears to be, as normally, eight, liut even on 

 the first node-bearing row, nodes may appear on the interspaces between the 

 angles of the prism and as many as twelve nodes may be counted upon the 

 second row in one of the specimens. The increase by intercalation is not, 

 however, always so rapid, as another example shows nine, with an incipient 

 tenth, in the second row. The nodes also multiply in another manner, namely 

 by the transverse division of a single node into two, or to express the fact 

 with greater accuracy, the appearance of two nodes one above the other in the 

 place usually occupied by one. This is seen on the specimens figured, Avhile 

 another example not here illustrated shows the duplication of all the nodes of 

 one row, thus making a complete double row of nodes. This interesting 

 mode of duplication of the nodes has not been observed in any American 

 species, but seems to indicate an approximation to the condition attained in 

 the genus Botryodictya. 



