28 SILICEOUS SPONGES. 



flint nodules. A great variety of forms of trifid and acerate spicules are found 

 commingled together. Rarely, too, in the clialk itself similar spicules are found 

 grouped together; but in this case the spicules are replaced by iron peroxide. 

 Specimens from Norfolk and the south of England. 



The spicules which thus occur in enormous numbers in the Oolite, the Lower and 

 Upper Green Sand, and the Upper Chalk are principally of Tetractinellid sponges, 

 and resemble those of the existing genera Geodia, Tethya, Stelletta, &c.; but their 

 forms are not sufficiently characteristic to allow a generic or specific determination 

 to be made from them. 



Order L I T H I S T I D .E, a Schmidt. 



Family RHIZ02I0RINA, Zittel. 



Genus CNEMIDIASTRUM, Zittel, 1878. 



CPfEMIDIASTRUM STELLATUM, GoMf. Sp. 



1833. Cnemidhm steUatum, Goldfuss, Petref. Th. 1, p. 15, t. 6. f. 2. 

 1833. Cnemidium gramdomm, Miinst., Goldf. Petref. p. 97, t. 35. f. 7. 



1878. Cnemispongia Goldfussi, Quenst. Petref. Bd. 5, p. 259, t. 126. f. 73^ 74, and t. 127. 

 f. 1-16. 



1878. Cnemidiastrum steUatum, Zitt. Studien, II Ab. p. 46, t. 3. f. 1, 2. 



1879. Cnemidiastrum steUatum, Zitt. Handbuch der Paloeont. Bd. 1, p. 150, f. 66. 



Bistrihution. Upper Jura : Randen, Heuberg ; Wiirtemberg. 



Cnemidiastrum striato-punctatdm, Goldf. sp. 



1833. Cnemidium striato-punctatum, Goldf. Petref. Th. 1, p. 15, t. 6. f. 3. 



1878. Cnemispongia Goldfussi, Queust. p. p. Petref. Bd. 5, p. 268, t. 127. f. 19-22. 



1878. Cnemidiastrum striato-punctatum, Zitt. Stud. II Ab. p. 46. 



Distribution. Upper Jura : Randen, Heuberg ; Wiirtemberg. 



Cnemidiastrum coR.iLLiNUM, Quenst. sp. 



1858. Cnemidium corallinum, Quenst. Der Jura, p. 694, t. 84. f. 1. 



1878. Cnemidium corallinum, Quenst. Petref. Bd. 5, p. 267, t. 127. f. 16-18. 



1878. Cnemidiastrum corallinum, Zitt. Stud. II Ab. p. 46. 



Distribtction. Upper Jura : Randen. 



Cnemidiastrum Hoheneggeri, Zitt. 



1878. Cnemidiastrum Holienegyeri, Zitt. Stud. II Ab. p. 46, t. 2. f. 8. 

 Microscopic slides with the spicules of this species, from Zittel's collection. 

 Distribution. Upper Jura : Wodna, Cracow. 



