M. K. A. Zittel on Fossil Calcispongiw. 125 



quently appear to be continued downwards into simple fine 

 tubes. 



The only species which certainly belongs here occurs in 

 the Middle Jura : — 



Lymnorea wami7for*V,Lamx.Exp. Meth.pl. lxxix. figs. 2-4; 

 Mich. Ic. pi. lvii. fig. 10. 



Stellispongia, D'Orb. 



Manon, AchUleum, Cnemidium auctt. 



Stellispongia, D'Orb. 



Stellispongia, Enaulofungia, Diasteroftingia, From. 



Stellispongia, IAmnoreiheles p. p., Laube. 



Stellispongia, Asterospongia, Desmospongia, Didesmospongia, Cerio- 



spongia, Etal. 

 Atehracia, Cncmiracia, Holoracia, Trachysphecion, Pom. 



Sponge simple or, more frequently, composite. Individuals 

 globular, semiglobular, clavate, or cylindrical ; stock often 

 nodular, clothed, almost always at the base, and sometimes 

 also on the sides, with a thick, wrinkled, dermal layer. Ver- 

 tex convex, with a shallow radiate osculum, into which open 

 a larger or smaller number of efferent canals. The round 

 ostia of the latter are situated partly at the bottom, partly on 

 the sides of the osculum ; the former are connected with 

 vertical, the latter with radial canals. The uppermost radial 

 canals are frequently open, and then form more or less im- 

 pressed radial furrows. Over all the rest of the surface of 

 the sponge-body, so far as it is not covered with epitheca, 

 there are smaller ostia, connected with vertical or oblique 

 incurrent canals. 



The anastomosing skeletal fibres are generally of consider- 

 able thickness. 



I have limited D'Orbigny's name Stellispongia to those 

 calcareous sponges which are characterized by radiate oscula 

 into which vertical and radial canals open, and by numerous 

 smaller ostia on the surface. The round orifices at the bottom 

 of the oscula have previously often been overlooked, but they 

 are wanting in no true Stellispongia. 



Fromentcl's genus Enaulofungia is founded upon an erro- 

 neous observation ; for upon the typical species (E. coraUina) 

 itself the ostia on the surface are very distinctly developed. 



The species belonging to this genus are from the Trias 

 Jura, and Cretaceous. 



a. From the Trias. 



1. Cnemidium rotulare, Miinst. Beitr. iv. Taf. i. fig. 20. 

 Cnemidium Manon, Miinst. ib. Taf. i. fig. 20? 

 Cnemidium astroites, Miinst. ib. Taf. i. fig. 24. 



