1 26 DlCTYOSPONGID^. 



surface. In Thysanodictya the reticulation of this surface is rendered 

 reguhuly quadrate by the crossing of the strands whicli are vertical in the 

 wall of the cup; the margins of the base are frequently puckered into low and 

 irregularly disposed nodes, the peripheral fi-ill being produced directly from 

 this margin. The aspect of this surface is somewhat similar to that in the 

 species Oncosella catinum, Rauff, from the Wenlock limestone*, although the 

 latter is a thick-bodied sponge, and in this respect unlike Tiiysajj^odictya, 

 Rauff is disposed to believe that Oncosella possessed one or more tufts of 

 anchoring spicules, though they have not yet been found, and that, therefore, 

 the sj>onge was not yet attached by this flattened base. Presumably, in 

 Thysanodictya, the basal attachment was essentially effected by the encircling 

 frill-like tuft. 



It may be added that all the species of this genus now known show evi- 

 dence of a sixth series of reticulating spicular bands, which produces an 

 extremely minute ultimate division of the quadrules. 



Thysanodictya Edwin-Halli, nom. nov. 



Platk XXIV, Figs. 1-9. 



1890. Dkiyopliiitoti? {Pliragmodictya) HalU, Hall. Ninth Ann. Rept. N. Y. 

 State Geologist, p. 59; Forty-third Ann. Rept. N. Y. State 

 Museum, p. 261. 



Sponge generally small, obconical or subclavate, narrowest above the 

 base, rapidly expanding to the aperture ; very variable in form, sometimes long 

 and extremely slender, at other times short and stout. Base somewhat 

 expanded, nearly flat, in some instances apparently concave ; nodose on 

 the periphery and with a broad marginal spicular frill extended downward or 

 over the surface of attachment. 



Meticulmn of the lateral walls coarse, the main spicular bands forming 

 vertically elongate quadrules measuring on an average 7x11 mm. The size of 

 these quadrules varies greatly in different individuals and in different parts of 

 the same individual. The subordinate reticulation even to the last degree, is 

 often retained, but does not in any way obscure the predominance of the main 

 ridges. These vertical and transverse ridges of the first and second series are 

 expanded into lamellae which lie vertical to the surface of the cup and are 

 free for a width of from 2 to 4 mm. At the base of the cup the vertical 

 ridges thicken and form a single series of sharp, nodiform periphei-al ridges 

 which may extend for a short distance on the surface of the flattened or 



•8«e Ra0ff; Palaeospongiologie, Part 1, p. 264, pi. vii, figs. 5-10 (especially fig. 7). 1894. 



