142 Dictyospongid.t;. 



« 



Hallodictya Cottoniana, sp. nov. 



Platk xli, Fig. 12. 



A j)ortioii of a frond, evidently of the mode of growth characterizing 

 this genus, is less irregular than the foregoing species in the nodulation of its 

 surface, which bears only low and inconspicuous elevations. The reticulation 

 is quite as sharply defined as in IT. Sciensis, but it is notably less regular and 

 lacks even the suggestion of arrangement about any point. Notwithstanding 

 this irregularity, the impression of the reticulum clearly pertains to one and 

 the same layer, there being no evidence that such irregularity is due in any 

 way to the overlapping and compression of the reticular walls. 



The single specimen observed is of small size, measuring 85 by 50 mm., 

 evidently not the entire extent of the frond. 



Locality. In the middle beds of the Chemung group, at Cotton hill, one 

 mile north of Avoca, associated with Hydnoceras multinodosum, Arystidictya 

 elegans and A. nodifera. (Collected by Jacob Van Deloo.) 



ACTINODICTYA, Hall. 



1890. AcUiwduiya, Hall. Ninth Ann. llept. N. Y. State Geol., p. 59 ; Forty- 

 third Ann. Kept. N. Y. State Museum; p. 261. 



This genus was constituted for explanate, somewhat irregularly growing 

 sponges, whose surface is depressed convex and whose form appears, from the 

 aspect of the majority of specimens, to have been broadly oval. The fronds 

 have not shown the mode of attachment, but the absence of any cicatrix, or 

 stem, may perhaps indicate that the sponge was fixed by a marginal foot-stalk. 

 There are among the living hexactinellids species having this explanate or 

 leaf-shaped aspect and attached by such a stalk-like basal extension ; and 

 these bodies may be compared with the Euryplegma auriculare as figured by 

 SciiULZE (Voyage of H. M. S. "Challenger"; Hexactinellida, pi. cii, fig. 1). 

 The surface of the specimens is crossed in all directions by ridges and lines 

 of various sizes representing the interlacing spicular bands, and yet, notwith- 

 standing the conspicuous irregularity in the disposition of these bands, every 

 specimen shows more or less distinctly a certain degree of rectangidar reticu- 

 lation among both the coarser and finer bands. The coarse bands are com- 

 paratively few in number, and the differences in size in the coarse and fine 

 ridges are gradational and never abrupt. The irregular intersection of the 

 various spicular bands gives the reticulum a some^vhat stellate aspect. 



In the living species, Walteria Flemiyvlngl^ Schulze (see work cited, pi. ix)^ 



