478 SUCCESSION IN TIME OF GENERA OF SPONGES. 



Upper Chalk are Opliiraphidites, Ttthyopsis, Stelleta, Geodia, Thenia, 

 and Pachastrella. The Triassic rocks have only yielded calcareous 

 sponges, among which are Colospongia, Enoplocoelia, Celyphia, &c., 

 chiefly known from the St. Cassian beds ; but some genera, like 

 Eudia, range through the Jurassic, and some, like Peronella, through 

 the Secondary rocks. Other Lower Secondary genera are Corynella, 

 which sends species to the Upper Greensand, Eusiphonella, Lym- 

 norea, Inobolia, Stellispongia, Diaplectia. The Upper Secondary rocks 

 yield Synopella, Oculospongia, Masmostoma, Raphidonema, Phare- 

 trospongia, and Pachytilodia. 



The Lithistid sponges are numerous in the Jurassic rocks of the 

 continent of Europe, though almost unrepresented in this country. 

 Among characteristic genera are Cnemidiastrum, Hyalotragos, Platy- 

 clionia Placonella, Melonella. The Neocomian period is barren, with 

 the exception of a species of Mastosia. The Upper Greensand yields 

 Chenendopora, which is also represented in the Chalk. Indeed, many 

 genera are common to these formations, such as Seliscothon, Jereica, 

 Doryderma, PJiymatella, Trachysycon, Siphonia, 1 Jerea. Other genera 

 characteristic of the Upper Greensand are Holodictyon, Pachypoterion, 

 Nematinion, Hdllirlwa, Kalpinella, and Rhopalospongia. Among the 

 genera limited to the Upper Chalk are Verruculina, Scytalia, Stachy- 

 spongia, Pachinion, Heterostinia, Aulaxinia, Callopegma, Nelumbia, 

 Bolospongia, Thecosiphonia, Thamnospongia, Pholidodadia, Ragadinia, 

 Plinthocella, and PJiymaplectia. 



The Hexactinellid sponges are largely represented in the Jurassic 

 strata of the Continent. Among them are Tremadictyon, Sphenaulax, 

 Platyteichisma, Trochobolus, Cypellia, Stauroderma, and Porospongia. 

 Of genera common to the Oolites and newer Secondary series may be 

 mentioned Craticularia (which ranges up to the Chalk), Sporadopyle 

 (which ranges to the Neocomian), Verrucoccelia, and Toulminia (which 

 range to the Chalk). Plocoscyphia ranges from the Neocomian to the 

 Chalk. The Upper Greensand is characterised by some peculiar types, 

 and contains others which range to the Chalk. Among the former are 

 Brachiospongia, Eubrochus, and Sderokalia. Among the genera which 

 appear first in the Upper Greensand and range to the Chalk are Lepto- 

 phragma, Guettardia, and Ophrystoma. Genera limited to the Chalk 

 comprise Strepliinia (found in the Grey Chalk), Pleurostoma, Aphro- 

 lidllistes, Ventriculites, Rhizopoterion, Sporadoscinia, Plolyblastidium, 

 CephaUtes, Camerospongia, Callodictyon, Diplodictyon, Cceloptycliium, 

 and Stauractinella. 



A few sponges have been described from Tertiary strata, but among 

 the Miocene genera of Lithistids Siphonia, Jerea, Chenenopora, and 

 Astrocladia reappear. 2 



Dr. Hinde regards Eeceptaculites, Ischadites, and Sphaerospongia 

 of the Silurian and Devonian rocks as Hexactinellid sponges. 



1 Sollas, Q. J. G. S., vol. xxxiii. 



2 M any species of British sponges are figured by Dr. Hinde in his catalogue of 

 the fossil sponges in the Geological department of the British Museum, 1883, 

 which see. See also Zittel : Handbuch der Palceontologie (Miinchen u. Leipzig). 



