M. K. A. Zittel on Fossil Lithistidce. 325 



riorly, and then anastomose. Intervening skeletal mass at 

 least twice as wide as tlie fissures. In unrubbed specimens 

 the radial fissures are seen to consist of vertical rows of canals, 

 the round pore-like apertures of which are quite distinct in 

 the furrows. Within the wall, also, the canals of a row are 

 often separated by a thin layer of skeletal mass ; but sometimes 

 they coalesce and form a sing-le fissure-canal traversing the 

 whole height of the wall. When these fissures are filled 

 with rock-mass which offers more resistance to weathering 

 than the skeleton, they project like radiating ridges at the 

 vertex, giving the sponge some resemblance to the calice of a 

 coral. 



When well preserved, the outer and inner surfaces of the 

 wall are clothed with a nearly smooth covering- layer, through 

 which the oscula of the radial canals either project as small 

 perforated warts or are simply pierced. Goldfuss figures a 

 specimen of C. stellahim with well-preserved oscula, under the 

 name of C. granulosum (Taf. xxxv. fig. 7). 



The skeletal elements, which are generally converted into 

 calc-spar, are of moderate size, crooked, irregular, branched at 

 the ends, and covered with pointed or blunt spiny excres- 

 cences. 



The name Cnemklium, applied by Goldfuss to this genus, 

 has been given up, although it has been adopted by Quenstedt 

 in South Germany for the cup- and top- shaped sponges with 

 radiate furrows from the Upper Jura. Goldfuss brought 

 together very different things under the name of Cnemidmm ; 

 and although it is evident that Cnemtdtum rimulosum and 

 stellatum were specially in mind in the formation of the 

 generic diagnosis, the first species {C. lamellosum) belongs to 

 the hexactinellid genus PachyteicMsma. Quenstedt in 1843 

 (Flotzgeb. p. 424) limited the name Cnemidium to the forms 



Mich. Ic.=Miclielin, H., Iconographie Zoopbytologique. Paris, 1840-47. 

 Pom. Pal.=:Pomel, A., Paleontologie oil description des animaux fos- 



siles de la province d'Orau : Zoophytes. Oran, 1872. 

 Quenst. Handb. = Quenstedt, F. A., Ilandbuch der Petrefactenkunde, 



2te Aufl. 1867. 

 Quenst. Jura = Quenstedt, F. A., Der Jura. Tiibingeu, 1858. 

 Quenst. Petr.= Quenstedt, F. A,, Petrefactenkunde Deutscblands, Bd. v. 



Korallen. Leipzig, 1877-78. 

 Reuss, Kr. = Keiiss, A. E., Die Versteinerungen der bohmischen Kreide- 



formatiou. Stuttgart, 1845. 

 Rcim. Kr.=Iionier, F. A., Die Versteinerungen der norddeutschen 



Kreideformation. Hannover, 1841. 

 Rom. Spong. = Ronier, F. A., '' Die Spongitarieii des norddeutschen Kreide- 



gebirges," Paliioutogr. xiii. 18()4. 

 Rom. Sad. = Homer, Ferd., Die ibssile Fauua der siliu'ischen Diluvial- 



Geschiebe von Sadewitz. Breslau, 1801. 



