420 ZOOLOGY, 



Peculiar Palceozoic Sponges. 



In rocks of the Devonian ijeriod and of the Chemung group of New 

 York, the Waverly beds of Ohio, and the Keokuk beds of Iowa and 

 Indiana, are found certain problematical fossils to which the generic 

 names Hydnoceras, JDictyophyton, and Uphantwnia have been given. 

 These fossils have been supjiosed by most palaeontologists to have been 

 plants related to the algse. Mr. R. P. Whitfield, of New York, has 

 recently sought to ascertain their affinities, and has come to the conclu- 

 sion that they were, in fact, of sponge origin. His later researches were 

 seconded by PrinciiJal Dawson, of McGill University, who now enter- 

 tains the same opinion. The organisms in question are more or less 

 elongated tubes, and " have been composed of a thin film or pellicle of 

 net- work made of longitudinal and horizontal threads which cross each 

 other at right angles"; when carefully examined "one set ai^pears to 

 pass on the outside and the other on the inside of the body." A Uphan- 

 Uenia from Indiana, which was later examined, exhibited the original 

 structure better and "retained the substance of the organism. Under 

 a hand-glass of moderate power it is seen to have been composed of 

 cylindrical threads of various sizes, now replaced by pjaite." It had 

 broad, radiating bands, and between them narrow, thread-like bands as 

 well as " circular," narrow or thread ones. " The broad bands are com- 

 posed of very fine thread-like spicules, and the narrow ones of much 

 stronger ones, while the thin film occupying the intermediate spaces is 

 composed of still smaller spicules, apparently arranged in radiating 

 manner." According to Principal Dawson, viewed as opaque objects, 

 " the reticulating bands are seen to be fascicles of slender cylindrical 

 rods or si)icules," and the spicules are " usually cylindrical and smooth," 

 but occasionally taper gently to a point. " In their present state they 

 appear as solid, shining rods of pyrite." It is aptly added, that " the 

 most puzzling fact" is " the mineral condition of the spicules, now wholly 

 replaced by pyrite." Nevertheless, "the study of the specimen" in 

 question "inclined" Princii^al Dawson "to regard it as more probably 

 a sponge" than as a fucoid, as he had previously supposed. (A. J. S., 

 (3,) XXII, pp. 53-54; 132-133.) 



Subsequently, Mr. C. D. Walcott re-examined a fossil from the Utica 

 slate, which he had described in 1879 as an alga, under the name Cyatho- 

 phycus, and now considers it likewise to have been a sponge. It exhib- 

 ited the same general features of structure as the Hynoceratidw and the 

 spicules in it, too, had been all apparently replaced by pyrite. (A. J. S.. 

 (3,) XXII, ])}). 394-395.) All the fossils referred to have been compared, 

 as to structure, with Unplectella, and it has been said that they exhibited 

 the greatest similarity to that genus, but doubtless it was meant in a 

 general manner, and not, as might be inferred, that there was any inti- 

 mate relationship, or, in fact, closer aftinity between the forms discussed 

 and the recent genus than Avith the living relatives of the last. 



