144 DlOTTOSPONGID^. 



CRYPTOBICTYA, Hall. 



1890. CryptoiUetija, Hall. Ninth Anji. Rept. N. Y. State Geologist, p. 60; 

 Forty-third Ann. Rept. N. Y. State Museum, p. 202. 



Irregularly growing, tuberose, coarsely nodose, and probably uninclosed 

 sponges, with a surface showing no reticulating spicular bands; the skeleton 

 being presiunably composed of extremely fine isolated spicules, except at the 

 summits of the nodes which show evidence of short tufts of prostalia. 



Athough these specimens do not, of themselves, clearly demonstrate their 

 title to a position among the hexactinellid sponges, yet in the light of the asso- 

 ciated generic structures, Hallodictya and Actinodictya, we are doubtless 

 justified in regarding them as Silicea, having a matted or felted reticulum of 

 very minute spicules, and nodes with distinct pi'ostalia developed at their 

 summit. 



In addition to this structure, the surface frequently presents a sort of 

 linear striation or brush of lines departing from the nodes or sweeping irregu- 

 larly over the concave spaces. 



Type, Cryptodictya Alleni, Hall. 



Cryptodictta Alleni, Hall. 



Platk XXXI, Figs. 3-6 ; Platb xxxii, Figs. 1-4. 



1890. Cryptodictya Alleni, Hall. Ninth Ann. Rept. N. Y. State Geol., 

 p. 60 ; Forty-third Ann. Rept. N. Y. State Museum, p. 262. 



Sponges of moderately large size, with a general tendency to a suboval 

 or elongate outline, and a depressed convex sux'face with abruptly deflected 

 margins. In the majority of the best preserved examples this margin is 

 clearly defined for more or less of its extent, showing that the form was frond- 

 shaped or scaphate, though highly irregular and tubei'ose in contour and vari- 

 able in outline. In one example the frond has been so enfolded by lateral 

 compression as to bring the edges close together and produce the appearance 

 of a nearly closed cup. The attachment of these bodies must have been 

 either by means of a foot-stalk or by the margins of the frond. The nodes 

 upon the surface are of various shapes and irregular in disposition ; usually a 

 number of small nodes are situated upon the summit of a large one, these 

 being connected by a more or less sharply defined ridge, an arrangement also 

 seen in the genus Hallodictya. The entire surface of the rock covered by 

 the frond is invariably tinted of a deep chocolate or reddish bro\vn, in 

 strong contrast to the color of the matrix. An obscure, irregular lineation of 



