Fo88il Sponges. 125 



Tetractinellid and Lithistid sponges ; but the sponges themselves Sponges, 

 are very seldom preserved. OAILERT 



The Gault is very poor in sponges ; but the Upper Greensand, wesf Side, 

 the Chalk Marl, and the Chloritic Marl of Eastbourne, near wall-casei 

 Folkestone, Blackdown (Devon), and more particularly in the 7 & 8. 

 vicinity of Warminster, Wiltshire, contain great numbers, which 

 still preserve their original form and structures. A large series is Ta|,ie. 

 exhibited. The principal Hexactinellid genera are Plocoscyphia, cases 

 Cralicularia, Stauronema, and Leptophragma. Lithistid sponges are ' 



very numerous, more particularly those belonging to the Megamorina case 8. 

 and Tetracladina family ; they comprise Doryderma, Pachypoterion, 

 Nematinioyiy Carterella, Siphonia, Hallirlioa^ Jerea, Kalpinella^ 

 Mhopalospongia, and Chenendopora. The Calcispongiae are less 

 prominent in these beds ; they include Peronidella, Corynella, 

 Tremacystia, Elasmostoma, Pharetroapongia, and Pachytilodia. 

 More particularly worthy of mention are the peculiar lobate 

 forms of the Lithistid Eallirhoa (Fig. 175) with long stems; the 



Fia. 175. — Hallirhoa costata, Lamx. Upper Greensand : "Warminster. 

 (Eeduced to one-fourth.) 



very perfect 8tpho7im from Blackdown; the large goblet forms of 

 Pachypoterion ] and the cylindrical and branching examples of 

 Doryderma (Fig. 177) from near Warminster. 



In the Chalk itself, comprising both the Upper and Lower or 

 Grey Chalk, the sponge fauna is perhaps more highly developed 

 than in the Upper Greensand, but the sponges themselves are less 

 favourably preserved. Those from the Upper Chalk of the South 



