INTKODUCTION. 



15 



and, as a rule, these features are more frequently recognizable in fossil examples than 

 the spicular structures. 



The following is a list of the different Orders, Families, and Genera in which the 

 fossil sponges referred to in the following pages are arranged. Genera of existing 

 sponges are only included when represented by fossil species. 



Class SPONGI^. 



Division I. SILICEOUS SPONGES. 



Order Monactinellid.e. 



Climacospongia, Hinck. 

 Lasiocladia, Hinde. 

 Reuiera, 0. Schmidt. 

 Dirrhopalunij Ridley. 

 Acanthorapliis, Hinde. 

 Spongilla, Lamarck. 

 Cliona, Grant. 



Order Tetractinellid^. 



Ophirapliidites, Carter. 

 Tethyopsis, Zittel. 

 Stelletta, O. Schmidt. 

 Geodia, Lamarck, 

 Thenea, Gray. 

 Pachastrella, 0. Sch. 



Order Lithistid^. 



Family Rhizomor[na. 

 Cnemidiastrum, Zittel. 

 Corallidium, Qiienst. 

 Hyalotragos, Zift. 

 Pyrgoclionia, Gold/. 

 Leiodorella, Zitt. 

 Platychonia, Zitt. 

 Bolidium, Zitt. 

 Chonella, Zitt. 

 Seliscothon, Zitt. 

 Chenendopora, Lam. 

 Verruculina^ Zitt. 

 Stichophyma, Pomel, 

 Jereica, Zitt. 



Scytalia, Zitt. 

 Stachyspongia^ Zitt. 

 Pachinion, Zitt. 



Family Megamorina. 



Placonella, Hinde. 

 Doryderma, Zitt. 

 Holodictyon, Hinde. 

 Pachypoterion, Hinde. 

 Heterostinia, Zitt. 

 Nematinion, Hinde. 

 Carterella, Zitt. 

 Isoraphinia, Zitt. 



Family Ano.mocladina. 



Cylindrophyma, Zitt. 

 Melonella, Zitt. 

 Lecanella, Zitt. 

 Mastosia, Zitt. 

 Hiudia, Duncan. 



Family Tetiiacladixa. 



Aulocopium, Osivatd. 

 Phymatella, Zitt. 

 Aulaxinia, Zitt. 

 Callopegma, Zitt. 

 Tracliysycon, Zitt. 

 Siphonia, Goldfuss. 

 Hallirhoaj Lamx. 

 Jerea, Lamx. 

 Nelumbia, Pomel. 

 Polyjerea, From. 

 Bolospongia, Hinde. 



