124 



Guide to the Invertebrata. 



Sponges. 

 GALLEKY 

 X. 



West Side. 



Wall-caaes 

 7& 8, 

 Table- 

 cases 

 11 15. 



Wall- 

 case 8. 



Table- 

 case 14. 



From the Carboniferous Limestone of Yorkshire there are well- 

 preserved examples of the anchoring spicular ropes of Hyalostelia 

 and small portions of the peculiar Tholiasterella and Asteractinella. 

 Detached spicules of Pachaslrella, Geodites, and Bcryderma, prove 

 the occurrence of these Tetractiuellid and Lithistid genera in the 

 Carboniferous period. 



Mesozoic, — From the Triassic strata of St. Cassian there is 

 a series of small Calcisponges which have been referred to Stelli- 

 spongia, Corynella, and other genera of Pharetrones. 



Prom the Great Oolite and the Corallian beds of this country 

 many fairly well - preserved Calcisponges have been obtained 

 belonging to Feronidella (Fig. 174), Corynella, JEusiphonella, Lymno- 

 rella, and Ilolcospongia, 



Fig. 174. — Peronidella pistilUformis, Lamx. Great Oolite 

 Cliff, near Bath, (Reduced one-half.) 



Hampton 



Wall- 

 case 8. 



Table- 

 case 14. 



The Upper or White Jurassic strata of "Wiirtemberg and Switzer- 

 land contain a large number of Lithistid and Hexactinellid 

 sponges, some beds of the rock being mainly composed of these 

 organisms. They retain their outer form, but in nearly all, the 

 siliceous skeleton has been replaced by calcite. A representative 

 scries is shown, comprising the Lithistid genera, Cnemidiastrum, 

 ITyalotragos, Pyrgochonia, Leiodorella, Platychonia, Placonelluy 

 Cylindrophyma, and Melonella, and the following Hexactinellids : 

 Tremadictyon, Craticulariay SphenauUx, Sporadopyle, VerrucocosUa, 

 Pachyleichisma, IVochobvlus, Cypellta, Stauroderma, Casearia, and 

 Porospongia. Some of these genera also occur in the Inferior 

 Oolite of Dorsetshire. 



Passing now to the Cretaceous system, the Lower Greensand of 

 Faringdon, in Berkshire, yields a great variety of Calcisponges, 

 retaining their forms very perfectly. They belong to Rhaphidonema, 

 Barrokia {Tremacydia), Peronidella, Corynella, JElasmocmlia, Oculo- 

 spongia, etc. The chtrt beds of the Lower Greensand in Kent 

 and Surrey are mainly composed of detached siliceous spicules of 



