Species of tiie Psammttrs dit Condroz. 149 



The reticulwm is very fine, as in //. Barroini, showing none of the coarner 

 meshes prevailing in the Chemung species of this genus. None of the speci- 

 mens are so preserved as to sho\v tufts at the end of the nodes. 



Dimensions. The most complete individual, which bears three horizontal 

 ro\vs of nodes and a considerable portion of an anodose base, has a length of 

 155 mm. and a width across the top (exaggerated by compression) of 100 mm. 



Locality. In the Psammites du Condroz, Jeumont, Brittany. 



RlIABDOSISPONGIA CoNDROZIANA, Sp. HOV. 

 Plate xlvii, Fios. 1, 2. 



This magnificient species shows some of the exterior characters of the 

 Chemung form, Dictyophyton AmaUliea, which has elsewhere been taken as 

 the type of the proposed genus Rhabdosisponoia. These are, briefly, the suc- 

 cessive annulations, separated by deep constrictions and crossed by vertical or 

 divergent ridges. 



In the French specimens the apical portion of the cup is regular and with- 

 out annulations for a considerable distance, the surface here being divided into 

 eight prism-faces. In the best preserved example the first annulation is, on 

 one side, an enormous bulging of the cup, which covers more than one-half 

 the length of the specimen and makes its greatest width. On the other side, 

 this large swelling is divided into two, by a broad constriction near its lower 

 portion, which extends rather more than half-way around the cup. This forms 

 a small annulation beneath and a large one above. The constriction above this 

 double annulation encircles the entire cup, but the succeeding swelling is of 

 less size and is apparently of equal width on both sides of the sponge. Above 

 this is evidence of a still fainter constriction and annulation, making in all 

 four annulations on the best preserved side. There are three specimens of 

 this species in the material at hand, and all of them show the tendency to 

 develop an annulation or swelling on one side earlier than on the other. To 

 this fact are due the slight curvature and lateral asymmetry of the sponge. 

 The eight vertical ridges near the base of the cup maintain themselves over 

 the entire extent of the sponge, diverging greatly as they pass over the 

 expanded portions. Their number is increased by the gradual appearance of 

 new ones at the center of the faces, but the latter are never so strong as the 

 primary ridges. 



The reticulum is fine-meshed throughout, as in the other species from this 

 horizon. 



